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Preface
The Spring Data Elasticsearch project applies core Spring concepts to the development of solutions using the Elasticsearch Search Engine. It provides:
-
Templates as a high-level abstraction for storing, searching, sorting documents and building aggregations.
-
Repositories which for example enable the user to express queries by defining interfaces having customized method names (for basic information about repositories see Working with Spring Data Repositories).
You will notice similarities to the Spring data solr and mongodb support in the Spring Framework.
1. What’s new
1.1. New in Spring Data Elasticsearch 4.1
-
Uses Spring 5.3.
-
Upgrade to Elasticsearch 7.9.3.
-
Improved API for alias management.
-
Introduction of
ReactiveIndexOperations
for index management. -
Index templates support.
-
Support for Geo-shape data with GeoJson.
1.2. New in Spring Data Elasticsearch 4.0
-
Uses Spring 5.2.
-
Upgrade to Elasticsearch 7.6.2.
-
Deprecation of
TransportClient
usage. -
Implements most of the mapping-types available for the index mappings.
-
Removal of the Jackson
ObjectMapper
, now using the MappingElasticsearchConverter -
Cleanup of the API in the
*Operations
interfaces, grouping and renaming methods so that they match the Elasticsearch API, deprecating the old methods, aligning with other Spring Data modules. -
Introduction of
SearchHit<T>
class to represent a found document together with the relevant result metadata for this document (i.e. sortValues). -
Introduction of the
SearchHits<T>
class to represent a whole search result together with the metadata for the complete search result (i.e. max_score). -
Introduction of
SearchPage<T>
class to represent a paged result containing aSearchHits<T>
instance. -
Introduction of the
GeoDistanceOrder
class to be able to create sorting by geographical distance -
Implementation of Auditing Support
-
Implementation of lifecycle entity callbacks
1.3. New in Spring Data Elasticsearch 3.2
-
Secured Elasticsearch cluster support with Basic Authentication and SSL transport.
-
Upgrade to Elasticsearch 6.8.1.
-
Reactive programming support with Reactive Elasticsearch Operations and Reactive Elasticsearch Repositories.
-
Introduction of the ElasticsearchEntityMapper as an alternative to the Jackson
ObjectMapper
. -
Field name customization in
@Field
. -
Support for Delete by Query.
2. Project Metadata
-
Version Control - https://github.com/spring-projects/spring-data-elasticsearch
-
API Documentation - https://docs.spring.io/spring-data/elasticsearch/docs/current/api/
-
Bugtracker - https://jira.spring.io/browse/DATAES
-
Release repository - https://repo.spring.io/libs-release
-
Milestone repository - https://repo.spring.io/libs-milestone
-
Snapshot repository - https://repo.spring.io/libs-snapshot
3. Requirements
Requires an installation of Elasticsearch.
3.1. Versions
The following table shows the Elasticsearch versions that are used by Spring Data release trains and version of Spring Data Elasticsearch included in that, as well as the Spring Boot versions referring to that particular Spring Data release train:
Spring Data Release Train | Spring Data Elasticsearch | Elasticsearch | Spring Boot |
---|---|---|---|
2020.0.0[1] |
4.1.x[1] |
7.9.3 |
2.3.x[1] |
Neumann |
4.0.x |
7.6.2 |
2.3.x |
Moore |
3.2.x |
6.8.12 |
2.2.x |
Lovelace |
3.1.x |
6.2.2 |
2.1.x |
Kay[2] |
3.0.x[2] |
5.5.0 |
2.0.x[2] |
Ingalls[2] |
2.1.x[2] |
2.4.0 |
1.5.x[2] |
Support for upcoming versions of Elasticsearch is being tracked and general compatibility should be given assuming the usage of the high-level REST client.
4. Working with Spring Data Repositories
The goal of the Spring Data repository abstraction is to significantly reduce the amount of boilerplate code required to implement data access layers for various persistence stores.
Spring Data repository documentation and your module This chapter explains the core concepts and interfaces of Spring Data repositories. The information in this chapter is pulled from the Spring Data Commons module. It uses the configuration and code samples for the Java Persistence API (JPA) module. You should adapt the XML namespace declaration and the types to be extended to the equivalents of the particular module that you use. “Namespace reference” covers XML configuration, which is supported across all Spring Data modules that support the repository API. “Repository query keywords” covers the query method keywords supported by the repository abstraction in general. For detailed information on the specific features of your module, see the chapter on that module of this document. |
4.1. Core concepts
The central interface in the Spring Data repository abstraction is Repository
. It takes the domain class to manage as well as the ID type of the domain class as type arguments. This interface acts primarily as a marker interface to capture the types to work with and to help you to discover interfaces that extend this one. The CrudRepository
interface provides sophisticated CRUD functionality for the entity class that is being managed.
CrudRepository
Interfacepublic interface CrudRepository<T, ID> extends Repository<T, ID> {
<S extends T> S save(S entity); (1)
Optional<T> findById(ID primaryKey); (2)
Iterable<T> findAll(); (3)
long count(); (4)
void delete(T entity); (5)
boolean existsById(ID primaryKey); (6)
// … more functionality omitted.
}
1 | Saves the given entity. |
2 | Returns the entity identified by the given ID. |
3 | Returns all entities. |
4 | Returns the number of entities. |
5 | Deletes the given entity. |
6 | Indicates whether an entity with the given ID exists. |
We also provide persistence technology-specific abstractions, such as JpaRepository or MongoRepository . Those interfaces extend CrudRepository and expose the capabilities of the underlying persistence technology in addition to the rather generic persistence technology-agnostic interfaces such as CrudRepository .
|
On top of the CrudRepository
, there is a PagingAndSortingRepository
abstraction that adds additional methods to ease paginated access to entities:
PagingAndSortingRepository
interfacepublic interface PagingAndSortingRepository<T, ID> extends CrudRepository<T, ID> {
Iterable<T> findAll(Sort sort);
Page<T> findAll(Pageable pageable);
}
To access the second page of User
by a page size of 20, you could do something like the following:
PagingAndSortingRepository<User, Long> repository = // … get access to a bean
Page<User> users = repository.findAll(PageRequest.of(1, 20));
In addition to query methods, query derivation for both count and delete queries is available. The following list shows the interface definition for a derived count query:
interface UserRepository extends CrudRepository<User, Long> {
long countByLastname(String lastname);
}
The following listing shows the interface definition for a derived delete query:
interface UserRepository extends CrudRepository<User, Long> {
long deleteByLastname(String lastname);
List<User> removeByLastname(String lastname);
}
4.2. Query Methods
Standard CRUD functionality repositories usually have queries on the underlying datastore. With Spring Data, declaring those queries becomes a four-step process:
-
Declare an interface extending Repository or one of its subinterfaces and type it to the domain class and ID type that it should handle, as shown in the following example:
interface PersonRepository extends Repository<Person, Long> { … }
-
Declare query methods on the interface.
interface PersonRepository extends Repository<Person, Long> { List<Person> findByLastname(String lastname); }
-
Set up Spring to create proxy instances for those interfaces, either with JavaConfig or with XML configuration.
-
To use Java configuration, create a class similar to the following:
import org.springframework.data.jpa.repository.config.EnableJpaRepositories; @EnableJpaRepositories class Config { … }
-
To use XML configuration, define a bean similar to the following:
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:jpa="http://www.springframework.org/schema/data/jpa" xsi:schemaLocation="http://www.springframework.org/schema/beans https://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/data/jpa https://www.springframework.org/schema/data/jpa/spring-jpa.xsd"> <jpa:repositories base-package="com.acme.repositories"/> </beans>
The JPA namespace is used in this example. If you use the repository abstraction for any other store, you need to change this to the appropriate namespace declaration of your store module. In other words, you should exchange
jpa
in favor of, for example,mongodb
.Also, note that the JavaConfig variant does not configure a package explicitly, because the package of the annotated class is used by default. To customize the package to scan, use one of the
basePackage…
attributes of the data-store-specific repository’s@Enable${store}Repositories
-annotation.
-
-
Inject the repository instance and use it, as shown in the following example:
class SomeClient { private final PersonRepository repository; SomeClient(PersonRepository repository) { this.repository = repository; } void doSomething() { List<Person> persons = repository.findByLastname("Matthews"); } }
The sections that follow explain each step in detail:
4.3. Defining Repository Interfaces
To define a repository interface, you first need to define a domain class-specific repository interface. The interface must extend Repository
and be typed to the domain class and an ID type. If you want to expose CRUD methods for that domain type, extend CrudRepository
instead of Repository
.
4.3.1. Fine-tuning Repository Definition
Typically, your repository interface extends Repository
, CrudRepository
, or PagingAndSortingRepository
. Alternatively, if you do not want to extend Spring Data interfaces, you can also annotate your repository interface with @RepositoryDefinition
. Extending CrudRepository
exposes a complete set of methods to manipulate your entities. If you prefer to be selective about the methods being exposed, copy the methods you want to expose from CrudRepository
into your domain repository.
Doing so lets you define your own abstractions on top of the provided Spring Data Repositories functionality. |
The following example shows how to selectively expose CRUD methods (findById
and save
, in this case):
@NoRepositoryBean
interface MyBaseRepository<T, ID> extends Repository<T, ID> {
Optional<T> findById(ID id);
<S extends T> S save(S entity);
}
interface UserRepository extends MyBaseRepository<User, Long> {
User findByEmailAddress(EmailAddress emailAddress);
}
In the prior example, you defined a common base interface for all your domain repositories and exposed findById(…)
as well as save(…)
.These methods are routed into the base repository implementation of the store of your choice provided by Spring Data (for example, if you use JPA, the implementation is SimpleJpaRepository
), because they match the method signatures in CrudRepository
. So the UserRepository
can now save users, find individual users by ID, and trigger a query to find Users
by email address.
The intermediate repository interface is annotated with @NoRepositoryBean . Make sure you add that annotation to all repository interfaces for which Spring Data should not create instances at runtime.
|
4.3.2. Using Repositories with Multiple Spring Data Modules
Using a unique Spring Data module in your application makes things simple, because all repository interfaces in the defined scope are bound to the Spring Data module. Sometimes, applications require using more than one Spring Data module. In such cases, a repository definition must distinguish between persistence technologies. When it detects multiple repository factories on the class path, Spring Data enters strict repository configuration mode. Strict configuration uses details on the repository or the domain class to decide about Spring Data module binding for a repository definition:
-
If the repository definition extends the module-specific repository, it is a valid candidate for the particular Spring Data module.
-
If the domain class is annotated with the module-specific type annotation, it is a valid candidate for the particular Spring Data module. Spring Data modules accept either third-party annotations (such as JPA’s
@Entity
) or provide their own annotations (such as@Document
for Spring Data MongoDB and Spring Data Elasticsearch).
The following example shows a repository that uses module-specific interfaces (JPA in this case):
interface MyRepository extends JpaRepository<User, Long> { }
@NoRepositoryBean
interface MyBaseRepository<T, ID> extends JpaRepository<T, ID> { … }
interface UserRepository extends MyBaseRepository<User, Long> { … }
MyRepository
and UserRepository
extend JpaRepository
in their type hierarchy. They are valid candidates for the Spring Data JPA module.
The following example shows a repository that uses generic interfaces:
interface AmbiguousRepository extends Repository<User, Long> { … }
@NoRepositoryBean
interface MyBaseRepository<T, ID> extends CrudRepository<T, ID> { … }
interface AmbiguousUserRepository extends MyBaseRepository<User, Long> { … }
AmbiguousRepository
and AmbiguousUserRepository
extend only Repository
and CrudRepository
in their type hierarchy. While this is fine when using a unique Spring Data module, multiple modules cannot distinguish to which particular Spring Data these repositories should be bound.
The following example shows a repository that uses domain classes with annotations:
interface PersonRepository extends Repository<Person, Long> { … }
@Entity
class Person { … }
interface UserRepository extends Repository<User, Long> { … }
@Document
class User { … }
PersonRepository
references Person
, which is annotated with the JPA @Entity
annotation, so this repository clearly belongs to Spring Data JPA. UserRepository
references User
, which is annotated with Spring Data MongoDB’s @Document
annotation.
The following bad example shows a repository that uses domain classes with mixed annotations:
interface JpaPersonRepository extends Repository<Person, Long> { … }
interface MongoDBPersonRepository extends Repository<Person, Long> { … }
@Entity
@Document
class Person { … }
This example shows a domain class using both JPA and Spring Data MongoDB annotations. It defines two repositories, JpaPersonRepository
and MongoDBPersonRepository
. One is intended for JPA and the other for MongoDB usage. Spring Data is no longer able to tell the repositories apart, which leads to undefined behavior.
Repository type details and distinguishing domain class annotations are used for strict repository configuration to identify repository candidates for a particular Spring Data module. Using multiple persistence technology-specific annotations on the same domain type is possible and enables reuse of domain types across multiple persistence technologies. However, Spring Data can then no longer determine a unique module with which to bind the repository.
The last way to distinguish repositories is by scoping repository base packages. Base packages define the starting points for scanning for repository interface definitions, which implies having repository definitions located in the appropriate packages. By default, annotation-driven configuration uses the package of the configuration class. The base package in XML-based configuration is mandatory.
The following example shows annotation-driven configuration of base packages:
@EnableJpaRepositories(basePackages = "com.acme.repositories.jpa")
@EnableMongoRepositories(basePackages = "com.acme.repositories.mongo")
class Configuration { … }
4.4. Defining Query Methods
The repository proxy has two ways to derive a store-specific query from the method name:
-
By deriving the query from the method name directly.
-
By using a manually defined query.
Available options depend on the actual store. However, there must be a strategy that decides what actual query is created. The next section describes the available options.
4.4.1. Query Lookup Strategies
The following strategies are available for the repository infrastructure to resolve the query. With XML configuration, you can configure the strategy at the namespace through the query-lookup-strategy
attribute. For Java configuration, you can use the queryLookupStrategy
attribute of the Enable${store}Repositories
annotation. Some strategies may not be supported for particular datastores.
-
CREATE
attempts to construct a store-specific query from the query method name. The general approach is to remove a given set of well known prefixes from the method name and parse the rest of the method. You can read more about query construction in “Query Creation”. -
USE_DECLARED_QUERY
tries to find a declared query and throws an exception if it cannot find one. The query can be defined by an annotation somewhere or declared by other means. See the documentation of the specific store to find available options for that store. If the repository infrastructure does not find a declared query for the method at bootstrap time, it fails. -
CREATE_IF_NOT_FOUND
(the default) combinesCREATE
andUSE_DECLARED_QUERY
. It looks up a declared query first, and, if no declared query is found, it creates a custom method name-based query. This is the default lookup strategy and, thus, is used if you do not configure anything explicitly. It allows quick query definition by method names but also custom-tuning of these queries by introducing declared queries as needed.
4.4.2. Query Creation
The query builder mechanism built into the Spring Data repository infrastructure is useful for building constraining queries over entities of the repository. The mechanism strips the find…By
, read…By
, query…By
, count…By
, and get…By
prefixes from the method and starts parsing the rest of it. The introducing clause can contain further expressions, such as a Distinct
to set a distinct flag on the query to be created. However, the first By
acts as a delimiter to indicate the start of the actual criteria. At a very basic level, you can define conditions on entity properties and concatenate them with And
and Or
. The following example shows how to create a number of queries:
interface PersonRepository extends Repository<Person, Long> {
List<Person> findByEmailAddressAndLastname(EmailAddress emailAddress, String lastname);
// Enables the distinct flag for the query
List<Person> findDistinctPeopleByLastnameOrFirstname(String lastname, String firstname);
List<Person> findPeopleDistinctByLastnameOrFirstname(String lastname, String firstname);
// Enabling ignoring case for an individual property
List<Person> findByLastnameIgnoreCase(String lastname);
// Enabling ignoring case for all suitable properties
List<Person> findByLastnameAndFirstnameAllIgnoreCase(String lastname, String firstname);
// Enabling static ORDER BY for a query
List<Person> findByLastnameOrderByFirstnameAsc(String lastname);
List<Person> findByLastnameOrderByFirstnameDesc(String lastname);
}
The actual result of parsing the method depends on the persistence store for which you create the query. However, there are some general things to notice:
-
The expressions are usually property traversals combined with operators that can be concatenated. You can combine property expressions with
AND
andOR
. You also get support for operators such asBetween
,LessThan
,GreaterThan
, andLike
for the property expressions. The supported operators can vary by datastore, so consult the appropriate part of your reference documentation. -
The method parser supports setting an
IgnoreCase
flag for individual properties (for example,findByLastnameIgnoreCase(…)
) or for all properties of a type that supports ignoring case (usuallyString
instances — for example,findByLastnameAndFirstnameAllIgnoreCase(…)
). Whether ignoring cases is supported may vary by store, so consult the relevant sections in the reference documentation for the store-specific query method. -
You can apply static ordering by appending an
OrderBy
clause to the query method that references a property and by providing a sorting direction (Asc
orDesc
). To create a query method that supports dynamic sorting, see “Special parameter handling”.
4.4.3. Property Expressions
Property expressions can refer only to a direct property of the managed entity, as shown in the preceding example. At query creation time, you already make sure that the parsed property is a property of the managed domain class. However, you can also define constraints by traversing nested properties. Consider the following method signature:
List<Person> findByAddressZipCode(ZipCode zipCode);
Assume a Person
has an Address
with a ZipCode
. In that case, the method creates the x.address.zipCode
property traversal. The resolution algorithm starts by interpreting the entire part (AddressZipCode
) as the property and checks the domain class for a property with that name (uncapitalized). If the algorithm succeeds, it uses that property. If not, the algorithm splits up the source at the camel-case parts from the right side into a head and a tail and tries to find the corresponding property — in our example, AddressZip
and Code
. If the algorithm finds a property with that head, it takes the tail and continues building the tree down from there, splitting the tail up in the way just described. If the first split does not match, the algorithm moves the split point to the left (Address
, ZipCode
) and continues.
Although this should work for most cases, it is possible for the algorithm to select the wrong property. Suppose the Person
class has an addressZip
property as well. The algorithm would match in the first split round already, choose the wrong property, and fail (as the type of addressZip
probably has no code
property).
To resolve this ambiguity you can use _
inside your method name to manually define traversal points. So our method name would be as follows:
List<Person> findByAddress_ZipCode(ZipCode zipCode);
Because we treat the underscore character as a reserved character, we strongly advise following standard Java naming conventions (that is, not using underscores in property names but using camel case instead).
4.4.4. Special parameter handling
To handle parameters in your query, define method parameters as already seen in the preceding examples. Besides that, the infrastructure recognizes certain specific types like Pageable
and Sort
, to apply pagination and sorting to your queries dynamically. The following example demonstrates these features:
Pageable
, Slice
, and Sort
in query methodsPage<User> findByLastname(String lastname, Pageable pageable);
Slice<User> findByLastname(String lastname, Pageable pageable);
List<User> findByLastname(String lastname, Sort sort);
List<User> findByLastname(String lastname, Pageable pageable);
APIs taking Sort and Pageable expect non-null values to be handed into methods.
If you do not want to apply any sorting or pagination, use Sort.unsorted() and Pageable.unpaged() .
|
The first method lets you pass an org.springframework.data.domain.Pageable
instance to the query method to dynamically add paging to your statically defined query. A Page
knows about the total number of elements and pages available. It does so by the infrastructure triggering a count query to calculate the overall number. As this might be expensive (depending on the store used), you can instead return a Slice
. A Slice
knows only about whether a next Slice
is available, which might be sufficient when walking through a larger result set.
Sorting options are handled through the Pageable
instance, too. If you need only sorting, add an org.springframework.data.domain.Sort
parameter to your method. As you can see, returning a List
is also possible. In this case, the additional metadata required to build the actual Page
instance is not created (which, in turn, means that the additional count query that would have been necessary is not issued). Rather, it restricts the query to look up only the given range of entities.
To find out how many pages you get for an entire query, you have to trigger an additional count query. By default, this query is derived from the query you actually trigger. |
Paging and Sorting
You can define simple sorting expressions by using property names. You can concatenate expressions to collect multiple criteria into one expression.
Sort sort = Sort.by("firstname").ascending()
.and(Sort.by("lastname").descending());
For a more type-safe way to define sort expressions, start with the type for which to define the sort expression and use method references to define the properties on which to sort.
TypedSort<Person> person = Sort.sort(Person.class);
Sort sort = person.by(Person::getFirstname).ascending()
.and(person.by(Person::getLastname).descending());
TypedSort.by(…) makes use of runtime proxies by (typically) using CGlib, which may interfere with native image compilation when using tools such as Graal VM Native.
|
If your store implementation supports Querydsl, you can also use the generated metamodel types to define sort expressions:
QSort sort = QSort.by(QPerson.firstname.asc())
.and(QSort.by(QPerson.lastname.desc()));
4.4.5. Limiting Query Results
You can limit the results of query methods by using the first
or top
keywords, which you can use interchangeably. You can append an optional numeric value to top
or first
to specify the maximum result size to be returned.
If the number is left out, a result size of 1 is assumed. The following example shows how to limit the query size:
Top
and First
User findFirstByOrderByLastnameAsc();
User findTopByOrderByAgeDesc();
Page<User> queryFirst10ByLastname(String lastname, Pageable pageable);
Slice<User> findTop3ByLastname(String lastname, Pageable pageable);
List<User> findFirst10ByLastname(String lastname, Sort sort);
List<User> findTop10ByLastname(String lastname, Pageable pageable);
The limiting expressions also support the Distinct
keyword. Also, for the queries that limit the result set to one instance, wrapping the result into with the Optional
keyword is supported.
If pagination or slicing is applied to a limiting query pagination (and the calculation of the number of available pages), it is applied within the limited result.
Limiting the results in combination with dynamic sorting by using a Sort parameter lets you express query methods for the 'K' smallest as well as for the 'K' biggest elements.
|
4.4.6. Repository Methods Returning Collections or Iterables
Query methods that return multiple results can use standard Java Iterable
, List
, and Set
.
Beyond that, we support returning Spring Data’s Streamable
, a custom extension of Iterable
, as well as collection types provided by Vavr.
Using Streamable as Query Method Return Type
You can use Streamable
as alternative to Iterable
or any collection type.
It provides convenience methods to access a non-parallel Stream
(missing from Iterable
) and the ability to directly ….filter(…)
and ….map(…)
over the elements and concatenate the Streamable
to others:
interface PersonRepository extends Repository<Person, Long> {
Streamable<Person> findByFirstnameContaining(String firstname);
Streamable<Person> findByLastnameContaining(String lastname);
}
Streamable<Person> result = repository.findByFirstnameContaining("av")
.and(repository.findByLastnameContaining("ea"));
Returning Custom Streamable Wrapper Types
Providing dedicated wrapper types for collections is a commonly used pattern to provide an API for a query result that returns multiple elements. Usually, these types are used by invoking a repository method returning a collection-like type and creating an instance of the wrapper type manually. You can avoid that additional step as Spring Data lets you use these wrapper types as query method return types if they meet the following criteria:
-
The type implements
Streamable
. -
The type exposes either a constructor or a static factory method named
of(…)
orvalueOf(…)
that takesStreamable
as an argument.
The following listing shows an example:
class Product { (1)
MonetaryAmount getPrice() { … }
}
@RequiredArgConstructor(staticName = "of")
class Products implements Streamable<Product> { (2)
private Streamable<Product> streamable;
public MonetaryAmount getTotal() { (3)
return streamable.stream() //
.map(Priced::getPrice)
.reduce(Money.of(0), MonetaryAmount::add);
}
}
interface ProductRepository implements Repository<Product, Long> {
Products findAllByDescriptionContaining(String text); (4)
}
1 | A Product entity that exposes API to access the product’s price. |
2 | A wrapper type for a Streamable<Product> that can be constructed by using Products.of(…) (factory method created with the Lombok annotation). |
3 | The wrapper type exposes an additional API, calculating new values on the Streamable<Product> . |
4 | That wrapper type can be used as a query method return type directly. You need not return Streamable<Product> and manually wrap it in the repository client. |
Support for Vavr Collections
Vavr is a library that embraces functional programming concepts in Java. It ships with a custom set of collection types that you can use as query method return types, as the following table shows:
Vavr collection type | Used Vavr implementation type | Valid Java source types |
---|---|---|
|
|
|
|
|
|
|
|
|
You can use the types in the first column (or subtypes thereof) as query method return types and get the types in the second column used as implementation type, depending on the Java type of the actual query result (third column).
Alternatively, you can declare Traversable
(the Vavr Iterable
equivalent), and we then derive the implementation class from the actual return value. That is, a java.util.List
is turned into a Vavr List
or Seq
, a java.util.Set
becomes a Vavr LinkedHashSet
Set
, and so on.
4.4.7. Null Handling of Repository Methods
As of Spring Data 2.0, repository CRUD methods that return an individual aggregate instance use Java 8’s Optional
to indicate the potential absence of a value.
Besides that, Spring Data supports returning the following wrapper types on query methods:
-
com.google.common.base.Optional
-
scala.Option
-
io.vavr.control.Option
Alternatively, query methods can choose not to use a wrapper type at all.
The absence of a query result is then indicated by returning null
.
Repository methods returning collections, collection alternatives, wrappers, and streams are guaranteed never to return null
but rather the corresponding empty representation.
See “Repository query return types” for details.
Nullability Annotations
You can express nullability constraints for repository methods by using Spring Framework’s nullability annotations.
They provide a tooling-friendly approach and opt-in null
checks during runtime, as follows:
-
@NonNullApi
: Used on the package level to declare that the default behavior for parameters and return values is, respectively, neither to accept nor to producenull
values. -
@NonNull
: Used on a parameter or return value that must not benull
(not needed on a parameter and return value where@NonNullApi
applies). -
@Nullable
: Used on a parameter or return value that can benull
.
Spring annotations are meta-annotated with JSR 305 annotations (a dormant but widely used JSR). JSR 305 meta-annotations let tooling vendors (such as IDEA, Eclipse, and Kotlin) provide null-safety support in a generic way, without having to hard-code support for Spring annotations.
To enable runtime checking of nullability constraints for query methods, you need to activate non-nullability on the package level by using Spring’s @NonNullApi
in package-info.java
, as shown in the following example:
package-info.java
@org.springframework.lang.NonNullApi
package com.acme;
Once non-null defaulting is in place, repository query method invocations get validated at runtime for nullability constraints.
If a query result violates the defined constraint, an exception is thrown. This happens when the method would return null
but is declared as non-nullable (the default with the annotation defined on the package in which the repository resides).
If you want to opt-in to nullable results again, selectively use @Nullable
on individual methods.
Using the result wrapper types mentioned at the start of this section continues to work as expected: an empty result is translated into the value that represents absence.
The following example shows a number of the techniques just described:
package com.acme; (1)
import org.springframework.lang.Nullable;
interface UserRepository extends Repository<User, Long> {
User getByEmailAddress(EmailAddress emailAddress); (2)
@Nullable
User findByEmailAddress(@Nullable EmailAddress emailAdress); (3)
Optional<User> findOptionalByEmailAddress(EmailAddress emailAddress); (4)
}
1 | The repository resides in a package (or sub-package) for which we have defined non-null behavior. |
2 | Throws an EmptyResultDataAccessException when the query does not produce a result. Throws an IllegalArgumentException when the emailAddress handed to the method is null . |
3 | Returns null when the query does not produce a result. Also accepts null as the value for emailAddress . |
4 | Returns Optional.empty() when the query does not produce a result. Throws an IllegalArgumentException when the emailAddress handed to the method is null . |
Nullability in Kotlin-based Repositories
Kotlin has the definition of nullability constraints baked into the language.
Kotlin code compiles to bytecode, which does not express nullability constraints through method signatures but rather through compiled-in metadata. Make sure to include the kotlin-reflect
JAR in your project to enable introspection of Kotlin’s nullability constraints.
Spring Data repositories use the language mechanism to define those constraints to apply the same runtime checks, as follows:
interface UserRepository : Repository<User, String> {
fun findByUsername(username: String): User (1)
fun findByFirstname(firstname: String?): User? (2)
}
1 | The method defines both the parameter and the result as non-nullable (the Kotlin default). The Kotlin compiler rejects method invocations that pass null to the method. If the query yields an empty result, an EmptyResultDataAccessException is thrown. |
2 | This method accepts null for the firstname parameter and returns null if the query does not produce a result. |
4.4.8. Streaming Query Results
You can process the results of query methods incrementally by using a Java 8 Stream<T>
as the return type. Instead of wrapping the query results in a Stream
, data store-specific methods are used to perform the streaming, as shown in the following example:
Stream<T>
@Query("select u from User u")
Stream<User> findAllByCustomQueryAndStream();
Stream<User> readAllByFirstnameNotNull();
@Query("select u from User u")
Stream<User> streamAllPaged(Pageable pageable);
A Stream potentially wraps underlying data store-specific resources and must, therefore, be closed after usage. You can either manually close the Stream by using the close() method or by using a Java 7 try-with-resources block, as shown in the following example:
|
Stream<T>
result in a try-with-resources
blocktry (Stream<User> stream = repository.findAllByCustomQueryAndStream()) {
stream.forEach(…);
}
Not all Spring Data modules currently support Stream<T> as a return type.
|
4.4.9. Asynchronous Query Results
You can run repository queries asynchronously by using Spring’s asynchronous method running capability. This means the method returns immediately upon invocation while the actual query occurs in a task that has been submitted to a Spring TaskExecutor
. Asynchronous queries differ from reactive queries and should not be mixed. See the store-specific documentation for more details on reactive support. The following example shows a number of asynchronous queries:
@Async
Future<User> findByFirstname(String firstname); (1)
@Async
CompletableFuture<User> findOneByFirstname(String firstname); (2)
@Async
ListenableFuture<User> findOneByLastname(String lastname); (3)
1 | Use java.util.concurrent.Future as the return type. |
2 | Use a Java 8 java.util.concurrent.CompletableFuture as the return type. |
3 | Use a org.springframework.util.concurrent.ListenableFuture as the return type. |
4.5. Creating Repository Instances
This section covers how to create instances and bean definitions for the defined repository interfaces. One way to do so is by using the Spring namespace that is shipped with each Spring Data module that supports the repository mechanism, although we generally recommend using Java configuration.
4.5.1. XML Configuration
Each Spring Data module includes a repositories
element that lets you define a base package that Spring scans for you, as shown in the following example:
<?xml version="1.0" encoding="UTF-8"?>
<beans:beans xmlns:beans="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://www.springframework.org/schema/data/jpa"
xsi:schemaLocation="http://www.springframework.org/schema/beans
https://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/data/jpa
https://www.springframework.org/schema/data/jpa/spring-jpa.xsd">
<repositories base-package="com.acme.repositories" />
</beans:beans>
In the preceding example, Spring is instructed to scan com.acme.repositories
and all its sub-packages for interfaces extending Repository
or one of its sub-interfaces.
For each interface found, the infrastructure registers the persistence technology-specific FactoryBean
to create the appropriate proxies that handle invocations of the query methods.
Each bean is registered under a bean name that is derived from the interface name, so an interface of UserRepository
would be registered under userRepository
.
Bean names for nested repository interfaces are prefixed with their enclosing type name.
The base-package
attribute allows wildcards so that you can define a pattern of scanned packages.
Using Filters
By default, the infrastructure picks up every interface that extends the persistence technology-specific Repository
sub-interface located under the configured base package and creates a bean instance for it. However, you might want more fine-grained control over which interfaces have bean instances created for them. To do so, use <include-filter />
and <exclude-filter />
elements inside the <repositories />
element. The semantics are exactly equivalent to the elements in Spring’s context namespace. For details, see the Spring reference documentation for these elements.
For example, to exclude certain interfaces from instantiation as repository beans, you could use the following configuration:
<repositories base-package="com.acme.repositories">
<context:exclude-filter type="regex" expression=".*SomeRepository" />
</repositories>
The preceding example excludes all interfaces ending in SomeRepository
from being instantiated.
4.5.2. Java Configuration
You can also trigger the repository infrastructure by using a store-specific @Enable${store}Repositories
annotation on a Java configuration class. For an introduction to Java-based configuration of the Spring container, see JavaConfig in the Spring reference documentation.
A sample configuration to enable Spring Data repositories resembles the following:
@Configuration
@EnableJpaRepositories("com.acme.repositories")
class ApplicationConfiguration {
@Bean
EntityManagerFactory entityManagerFactory() {
// …
}
}
The preceding example uses the JPA-specific annotation, which you would change according to the store module you actually use. The same applies to the definition of the EntityManagerFactory bean. See the sections covering the store-specific configuration.
|
4.5.3. Standalone Usage
You can also use the repository infrastructure outside of a Spring container — for example, in CDI environments. You still need some Spring libraries in your classpath, but, generally, you can set up repositories programmatically as well. The Spring Data modules that provide repository support ship with a persistence technology-specific RepositoryFactory
that you can use, as follows:
RepositoryFactorySupport factory = … // Instantiate factory here
UserRepository repository = factory.getRepository(UserRepository.class);
4.6. Custom Implementations for Spring Data Repositories
This section covers repository customization and how fragments form a composite repository.
When a query method requires a different behavior or cannot be implemented by query derivation, you need to provide a custom implementation. Spring Data repositories let you provide custom repository code and integrate it with generic CRUD abstraction and query method functionality.
4.6.1. Customizing Individual Repositories
To enrich a repository with custom functionality, you must first define a fragment interface and an implementation for the custom functionality, as follows:
interface CustomizedUserRepository {
void someCustomMethod(User user);
}
class CustomizedUserRepositoryImpl implements CustomizedUserRepository {
public void someCustomMethod(User user) {
// Your custom implementation
}
}
The most important part of the class name that corresponds to the fragment interface is the Impl postfix.
|
The implementation itself does not depend on Spring Data and can be a regular Spring bean. Consequently, you can use standard dependency injection behavior to inject references to other beans (such as a JdbcTemplate
), take part in aspects, and so on.
Then you can let your repository interface extend the fragment interface, as follows:
interface UserRepository extends CrudRepository<User, Long>, CustomizedUserRepository {
// Declare query methods here
}
Extending the fragment interface with your repository interface combines the CRUD and custom functionality and makes it available to clients.
Spring Data repositories are implemented by using fragments that form a repository composition. Fragments are the base repository, functional aspects (such as QueryDsl), and custom interfaces along with their implementations. Each time you add an interface to your repository interface, you enhance the composition by adding a fragment. The base repository and repository aspect implementations are provided by each Spring Data module.
The following example shows custom interfaces and their implementations:
interface HumanRepository {
void someHumanMethod(User user);
}
class HumanRepositoryImpl implements HumanRepository {
public void someHumanMethod(User user) {
// Your custom implementation
}
}
interface ContactRepository {
void someContactMethod(User user);
User anotherContactMethod(User user);
}
class ContactRepositoryImpl implements ContactRepository {
public void someContactMethod(User user) {
// Your custom implementation
}
public User anotherContactMethod(User user) {
// Your custom implementation
}
}
The following example shows the interface for a custom repository that extends CrudRepository
:
interface UserRepository extends CrudRepository<User, Long>, HumanRepository, ContactRepository {
// Declare query methods here
}
Repositories may be composed of multiple custom implementations that are imported in the order of their declaration. Custom implementations have a higher priority than the base implementation and repository aspects. This ordering lets you override base repository and aspect methods and resolves ambiguity if two fragments contribute the same method signature. Repository fragments are not limited to use in a single repository interface. Multiple repositories may use a fragment interface, letting you reuse customizations across different repositories.
The following example shows a repository fragment and its implementation:
save(…)
interface CustomizedSave<T> {
<S extends T> S save(S entity);
}
class CustomizedSaveImpl<T> implements CustomizedSave<T> {
public <S extends T> S save(S entity) {
// Your custom implementation
}
}
The following example shows a repository that uses the preceding repository fragment:
interface UserRepository extends CrudRepository<User, Long>, CustomizedSave<User> {
}
interface PersonRepository extends CrudRepository<Person, Long>, CustomizedSave<Person> {
}
Configuration
If you use namespace configuration, the repository infrastructure tries to autodetect custom implementation fragments by scanning for classes below the package in which it found a repository. These classes need to follow the naming convention of appending the namespace element’s repository-impl-postfix
attribute to the fragment interface name. This postfix defaults to Impl
. The following example shows a repository that uses the default postfix and a repository that sets a custom value for the postfix:
<repositories base-package="com.acme.repository" />
<repositories base-package="com.acme.repository" repository-impl-postfix="MyPostfix" />
The first configuration in the preceding example tries to look up a class called com.acme.repository.CustomizedUserRepositoryImpl
to act as a custom repository implementation. The second example tries to look up com.acme.repository.CustomizedUserRepositoryMyPostfix
.
Resolution of Ambiguity
If multiple implementations with matching class names are found in different packages, Spring Data uses the bean names to identify which one to use.
Given the following two custom implementations for the CustomizedUserRepository
shown earlier, the first implementation is used.
Its bean name is customizedUserRepositoryImpl
, which matches that of the fragment interface (CustomizedUserRepository
) plus the postfix Impl
.
package com.acme.impl.one;
class CustomizedUserRepositoryImpl implements CustomizedUserRepository {
// Your custom implementation
}
package com.acme.impl.two;
@Component("specialCustomImpl")
class CustomizedUserRepositoryImpl implements CustomizedUserRepository {
// Your custom implementation
}
If you annotate the UserRepository
interface with @Component("specialCustom")
, the bean name plus Impl
then matches the one defined for the repository implementation in com.acme.impl.two
, and it is used instead of the first one.
Manual Wiring
If your custom implementation uses annotation-based configuration and autowiring only, the preceding approach shown works well, because it is treated as any other Spring bean. If your implementation fragment bean needs special wiring, you can declare the bean and name it according to the conventions described in the preceding section. The infrastructure then refers to the manually defined bean definition by name instead of creating one itself. The following example shows how to manually wire a custom implementation:
<repositories base-package="com.acme.repository" />
<beans:bean id="userRepositoryImpl" class="…">
<!-- further configuration -->
</beans:bean>
4.6.2. Customize the Base Repository
The approach described in the preceding section requires customization of each repository interfaces when you want to customize the base repository behavior so that all repositories are affected. To instead change behavior for all repositories, you can create an implementation that extends the persistence technology-specific repository base class. This class then acts as a custom base class for the repository proxies, as shown in the following example:
class MyRepositoryImpl<T, ID>
extends SimpleJpaRepository<T, ID> {
private final EntityManager entityManager;
MyRepositoryImpl(JpaEntityInformation entityInformation,
EntityManager entityManager) {
super(entityInformation, entityManager);
// Keep the EntityManager around to used from the newly introduced methods.
this.entityManager = entityManager;
}
@Transactional
public <S extends T> S save(S entity) {
// implementation goes here
}
}
The class needs to have a constructor of the super class which the store-specific repository factory implementation uses. If the repository base class has multiple constructors, override the one taking an EntityInformation plus a store specific infrastructure object (such as an EntityManager or a template class).
|
The final step is to make the Spring Data infrastructure aware of the customized repository base class. In Java configuration, you can do so by using the repositoryBaseClass
attribute of the @Enable${store}Repositories
annotation, as shown in the following example:
@Configuration
@EnableJpaRepositories(repositoryBaseClass = MyRepositoryImpl.class)
class ApplicationConfiguration { … }
A corresponding attribute is available in the XML namespace, as shown in the following example:
<repositories base-package="com.acme.repository"
base-class="….MyRepositoryImpl" />
4.7. Publishing Events from Aggregate Roots
Entities managed by repositories are aggregate roots.
In a Domain-Driven Design application, these aggregate roots usually publish domain events.
Spring Data provides an annotation called @DomainEvents
that you can use on a method of your aggregate root to make that publication as easy as possible, as shown in the following example:
class AnAggregateRoot {
@DomainEvents (1)
Collection<Object> domainEvents() {
// … return events you want to get published here
}
@AfterDomainEventPublication (2)
void callbackMethod() {
// … potentially clean up domain events list
}
}
1 | The method that uses @DomainEvents can return either a single event instance or a collection of events. It must not take any arguments. |
2 | After all events have been published, we have a method annotated with @AfterDomainEventPublication . You can use it to potentially clean the list of events to be published (among other uses). |
The methods are called every time one of a Spring Data repository’s save(…)
, saveAll(…)
, delete(…)
or deleteAll(…)
methods are called.
4.8. Spring Data Extensions
This section documents a set of Spring Data extensions that enable Spring Data usage in a variety of contexts. Currently, most of the integration is targeted towards Spring MVC.
4.8.1. Querydsl Extension
Querydsl is a framework that enables the construction of statically typed SQL-like queries through its fluent API.
Several Spring Data modules offer integration with Querydsl through QuerydslPredicateExecutor
, as the following example shows:
public interface QuerydslPredicateExecutor<T> {
Optional<T> findById(Predicate predicate); (1)
Iterable<T> findAll(Predicate predicate); (2)
long count(Predicate predicate); (3)
boolean exists(Predicate predicate); (4)
// … more functionality omitted.
}
1 | Finds and returns a single entity matching the Predicate . |
2 | Finds and returns all entities matching the Predicate . |
3 | Returns the number of entities matching the Predicate . |
4 | Returns whether an entity that matches the Predicate exists. |
To use the Querydsl support, extend QuerydslPredicateExecutor
on your repository interface, as the following example shows:
interface UserRepository extends CrudRepository<User, Long>, QuerydslPredicateExecutor<User> {
}
The preceding example lets you write type-safe queries by using Querydsl Predicate
instances, as the following example shows:
Predicate predicate = user.firstname.equalsIgnoreCase("dave")
.and(user.lastname.startsWithIgnoreCase("mathews"));
userRepository.findAll(predicate);
4.8.2. Web support
This section contains the documentation for the Spring Data web support as it is implemented in the current versions of Spring Data Commons. As the newly introduced support changes many things, we kept the documentation of the former behavior in [web.legacy]. |
Spring Data modules that support the repository programming model ship with a variety of web support. The web related components require Spring MVC JARs to be on the classpath. Some of them even provide integration with Spring HATEOAS. In general, the integration support is enabled by using the @EnableSpringDataWebSupport
annotation in your JavaConfig configuration class, as the following example shows:
@Configuration
@EnableWebMvc
@EnableSpringDataWebSupport
class WebConfiguration {}
The @EnableSpringDataWebSupport
annotation registers a few components. We discuss those later in this section. It also detects Spring HATEOAS on the classpath and registers integration components (if present) for it as well.
Alternatively, if you use XML configuration, register either SpringDataWebConfiguration
or HateoasAwareSpringDataWebConfiguration
as Spring beans, as the following example shows (for SpringDataWebConfiguration
):
<bean class="org.springframework.data.web.config.SpringDataWebConfiguration" />
<!-- If you use Spring HATEOAS, register this one *instead* of the former -->
<bean class="org.springframework.data.web.config.HateoasAwareSpringDataWebConfiguration" />
Basic Web Support
The configuration shown in the previous section registers a few basic components:
-
A Using the
DomainClassConverter
Class to let Spring MVC resolve instances of repository-managed domain classes from request parameters or path variables. -
HandlerMethodArgumentResolver
implementations to let Spring MVC resolvePageable
andSort
instances from request parameters.
Using the DomainClassConverter
Class
The DomainClassConverter
class lets you use domain types in your Spring MVC controller method signatures directly so that you need not manually lookup the instances through the repository, as the following example shows:
@Controller
@RequestMapping("/users")
class UserController {
@RequestMapping("/{id}")
String showUserForm(@PathVariable("id") User user, Model model) {
model.addAttribute("user", user);
return "userForm";
}
}
The method receives a User
instance directly, and no further lookup is necessary. The instance can be resolved by letting Spring MVC convert the path variable into the id
type of the domain class first and eventually access the instance through calling findById(…)
on the repository instance registered for the domain type.
Currently, the repository has to implement CrudRepository to be eligible to be discovered for conversion.
|
HandlerMethodArgumentResolvers for Pageable and Sort
The configuration snippet shown in the previous section also registers a PageableHandlerMethodArgumentResolver
as well as an instance of SortHandlerMethodArgumentResolver
. The registration enables Pageable
and Sort
as valid controller method arguments, as the following example shows:
@Controller
@RequestMapping("/users")
class UserController {
private final UserRepository repository;
UserController(UserRepository repository) {
this.repository = repository;
}
@RequestMapping
String showUsers(Model model, Pageable pageable) {
model.addAttribute("users", repository.findAll(pageable));
return "users";
}
}
The preceding method signature causes Spring MVC try to derive a Pageable
instance from the request parameters by using the following default configuration:
|
Page you want to retrieve. 0-indexed and defaults to 0. |
|
Size of the page you want to retrieve. Defaults to 20. |
|
Properties that should be sorted by in the format |
To customize this behavior, register a bean that implements the PageableHandlerMethodArgumentResolverCustomizer
interface or the SortHandlerMethodArgumentResolverCustomizer
interface, respectively. Its customize()
method gets called, letting you change settings, as the following example shows:
@Bean SortHandlerMethodArgumentResolverCustomizer sortCustomizer() {
return s -> s.setPropertyDelimiter("<-->");
}
If setting the properties of an existing MethodArgumentResolver
is not sufficient for your purpose, extend either SpringDataWebConfiguration
or the HATEOAS-enabled equivalent, override the pageableResolver()
or sortResolver()
methods, and import your customized configuration file instead of using the @Enable
annotation.
If you need multiple Pageable
or Sort
instances to be resolved from the request (for multiple tables, for example), you can use Spring’s @Qualifier
annotation to distinguish one from another. The request parameters then have to be prefixed with ${qualifier}_
. The following example shows the resulting method signature:
String showUsers(Model model,
@Qualifier("thing1") Pageable first,
@Qualifier("thing2") Pageable second) { … }
You have to populate thing1_page
, thing2_page
, and so on.
The default Pageable
passed into the method is equivalent to a PageRequest.of(0, 20)
, but you can customize it by using the @PageableDefault
annotation on the Pageable
parameter.
Hypermedia Support for Pageables
Spring HATEOAS ships with a representation model class (PagedResources
) that allows enriching the content of a Page
instance with the necessary Page
metadata as well as links to let the clients easily navigate the pages. The conversion of a Page
to a PagedResources
is done by an implementation of the Spring HATEOAS ResourceAssembler
interface, called the PagedResourcesAssembler
. The following example shows how to use a PagedResourcesAssembler
as a controller method argument:
@Controller
class PersonController {
@Autowired PersonRepository repository;
@RequestMapping(value = "/persons", method = RequestMethod.GET)
HttpEntity<PagedResources<Person>> persons(Pageable pageable,
PagedResourcesAssembler assembler) {
Page<Person> persons = repository.findAll(pageable);
return new ResponseEntity<>(assembler.toResources(persons), HttpStatus.OK);
}
}
Enabling the configuration, as shown in the preceding example, lets the PagedResourcesAssembler
be used as a controller method argument. Calling toResources(…)
on it has the following effects:
-
The content of the
Page
becomes the content of thePagedResources
instance. -
The
PagedResources
object gets aPageMetadata
instance attached, and it is populated with information from thePage
and the underlyingPageRequest
. -
The
PagedResources
may getprev
andnext
links attached, depending on the page’s state. The links point to the URI to which the method maps. The pagination parameters added to the method match the setup of thePageableHandlerMethodArgumentResolver
to make sure the links can be resolved later.
Assume we have 30 Person
instances in the database. You can now trigger a request (GET http://localhost:8080/persons
) and see output similar to the following:
{ "links" : [ { "rel" : "next",
"href" : "http://localhost:8080/persons?page=1&size=20" }
],
"content" : [
… // 20 Person instances rendered here
],
"pageMetadata" : {
"size" : 20,
"totalElements" : 30,
"totalPages" : 2,
"number" : 0
}
}
The assembler produced the correct URI and also picked up the default configuration to resolve the parameters into a Pageable
for an upcoming request. This means that, if you change that configuration, the links automatically adhere to the change. By default, the assembler points to the controller method it was invoked in, but you can customize that by passing a custom Link
to be used as base to build the pagination links, which overloads the PagedResourcesAssembler.toResource(…)
method.
Web Databinding Support
You can use Spring Data projections (described in [projections]) to bind incoming request payloads by using either JSONPath expressions (requires Jayway JsonPath or XPath expressions (requires XmlBeam), as the following example shows:
@ProjectedPayload
public interface UserPayload {
@XBRead("//firstname")
@JsonPath("$..firstname")
String getFirstname();
@XBRead("/lastname")
@JsonPath({ "$.lastname", "$.user.lastname" })
String getLastname();
}
You can use the type shown in the preceding example as a Spring MVC handler method argument or by using ParameterizedTypeReference
on one of methods of the RestTemplate
.
The preceding method declarations would try to find firstname
anywhere in the given document.
The lastname
XML lookup is performed on the top-level of the incoming document.
The JSON variant of that tries a top-level lastname
first but also tries lastname
nested in a user
sub-document if the former does not return a value.
That way, changes in the structure of the source document can be mitigated easily without having clients calling the exposed methods (usually a drawback of class-based payload binding).
Nested projections are supported as described in [projections].
If the method returns a complex, non-interface type, a Jackson ObjectMapper
is used to map the final value.
For Spring MVC, the necessary converters are registered automatically as soon as @EnableSpringDataWebSupport
is active and the required dependencies are available on the classpath.
For usage with RestTemplate
, register a ProjectingJackson2HttpMessageConverter
(JSON) or XmlBeamHttpMessageConverter
manually.
For more information, see the web projection example in the canonical Spring Data Examples repository.
Querydsl Web Support
For those stores that have QueryDSL integration, you can derive queries from the attributes contained in a Request
query string.
Consider the following query string:
?firstname=Dave&lastname=Matthews
Given the User
object from the previous examples, you can resolve a query string to the following value by using the QuerydslPredicateArgumentResolver
, as follows:
QUser.user.firstname.eq("Dave").and(QUser.user.lastname.eq("Matthews"))
The feature is automatically enabled, along with @EnableSpringDataWebSupport , when Querydsl is found on the classpath.
|
Adding a @QuerydslPredicate
to the method signature provides a ready-to-use Predicate
, which you can run by using the QuerydslPredicateExecutor
.
Type information is typically resolved from the method’s return type. Since that information does not necessarily match the domain type, it might be a good idea to use the root attribute of QuerydslPredicate .
|
The following example shows how to use @QuerydslPredicate
in a method signature:
@Controller
class UserController {
@Autowired UserRepository repository;
@RequestMapping(value = "/", method = RequestMethod.GET)
String index(Model model, @QuerydslPredicate(root = User.class) Predicate predicate, (1)
Pageable pageable, @RequestParam MultiValueMap<String, String> parameters) {
model.addAttribute("users", repository.findAll(predicate, pageable));
return "index";
}
}
1 | Resolve query string arguments to matching Predicate for User . |
The default binding is as follows:
-
Object
on simple properties aseq
. -
Object
on collection like properties ascontains
. -
Collection
on simple properties asin
.
You can customize those bindings through the bindings
attribute of @QuerydslPredicate
or by making use of Java 8 default methods
and adding the QuerydslBinderCustomizer
method to the repository interface, as follows:
interface UserRepository extends CrudRepository<User, String>,
QuerydslPredicateExecutor<User>, (1)
QuerydslBinderCustomizer<QUser> { (2)
@Override
default void customize(QuerydslBindings bindings, QUser user) {
bindings.bind(user.username).first((path, value) -> path.contains(value)) (3)
bindings.bind(String.class)
.first((StringPath path, String value) -> path.containsIgnoreCase(value)); (4)
bindings.excluding(user.password); (5)
}
}
1 | QuerydslPredicateExecutor provides access to specific finder methods for Predicate . |
2 | QuerydslBinderCustomizer defined on the repository interface is automatically picked up and shortcuts @QuerydslPredicate(bindings=…) . |
3 | Define the binding for the username property to be a simple contains binding. |
4 | Define the default binding for String properties to be a case-insensitive contains match. |
5 | Exclude the password property from Predicate resolution. |
4.8.3. Repository Populators
If you work with the Spring JDBC module, you are probably familiar with the support for populating a DataSource
with SQL scripts. A similar abstraction is available on the repositories level, although it does not use SQL as the data definition language because it must be store-independent. Thus, the populators support XML (through Spring’s OXM abstraction) and JSON (through Jackson) to define data with which to populate the repositories.
Assume you have a file called data.json
with the following content:
[ { "_class" : "com.acme.Person",
"firstname" : "Dave",
"lastname" : "Matthews" },
{ "_class" : "com.acme.Person",
"firstname" : "Carter",
"lastname" : "Beauford" } ]
You can populate your repositories by using the populator elements of the repository namespace provided in Spring Data Commons. To populate the preceding data to your PersonRepository
, declare a populator similar to the following:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:repository="http://www.springframework.org/schema/data/repository"
xsi:schemaLocation="http://www.springframework.org/schema/beans
https://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/data/repository
https://www.springframework.org/schema/data/repository/spring-repository.xsd">
<repository:jackson2-populator locations="classpath:data.json" />
</beans>
The preceding declaration causes the data.json
file to
be read and deserialized by a Jackson ObjectMapper
.
The type to which the JSON object is unmarshalled is determined by inspecting the _class
attribute of the JSON document. The infrastructure eventually selects the appropriate repository to handle the object that was deserialized.
To instead use XML to define the data the repositories should be populated with, you can use the unmarshaller-populator
element. You configure it to use one of the XML marshaller options available in Spring OXM. See the Spring reference documentation for details. The following example shows how to unmarshall a repository populator with JAXB:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:repository="http://www.springframework.org/schema/data/repository"
xmlns:oxm="http://www.springframework.org/schema/oxm"
xsi:schemaLocation="http://www.springframework.org/schema/beans
https://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/data/repository
https://www.springframework.org/schema/data/repository/spring-repository.xsd
http://www.springframework.org/schema/oxm
https://www.springframework.org/schema/oxm/spring-oxm.xsd">
<repository:unmarshaller-populator locations="classpath:data.json"
unmarshaller-ref="unmarshaller" />
<oxm:jaxb2-marshaller contextPath="com.acme" />
</beans>
Reference Documentation
5. Elasticsearch Clients
This chapter illustrates configuration and usage of supported Elasticsearch client implementations.
Spring Data Elasticsearch operates upon an Elasticsearch client that is connected to a single Elasticsearch node or a cluster. Although the Elasticsearch Client can be used to work with the cluster, applications using Spring Data Elasticsearch normally use the higher level abstractions of Elasticsearch Operations and Elasticsearch Repositories.
5.1. Transport Client
The well known TransportClient is deprecated as of Elasticsearch 7 and will be removed in Elasticsearch 8. (see the Elasticsearch documentation). Spring Data Elasticsearch will support the TransportClient as long as it is available in the used
Elasticsearch version but has deprecated the classes using it since version 4.0.
|
We strongly recommend to use the High Level REST Client instead of the TransportClient
.
@Configuration
public class TransportClientConfig extends ElasticsearchConfigurationSupport {
@Bean
public Client elasticsearchClient() throws UnknownHostException {
Settings settings = Settings.builder().put("cluster.name", "elasticsearch").build(); (1)
TransportClient client = new PreBuiltTransportClient(settings);
client.addTransportAddress(new TransportAddress(InetAddress.getByName("127.0.0.1"), 9300)); (2)
return client;
}
@Bean(name = { "elasticsearchOperations", "elasticsearchTemplate" })
public ElasticsearchTemplate elasticsearchTemplate() throws UnknownHostException {
return new ElasticsearchTemplate(elasticsearchClient());
}
}
// ...
IndexRequest request = new IndexRequest("spring-data", "elasticsearch", randomID())
.source(someObject)
.setRefreshPolicy(IMMEDIATE);
IndexResponse response = client.index(request);
1 | The TransportClient must be configured with the cluster name. |
2 | The host and port to connect the client to. |
5.2. High Level REST Client
The Java High Level REST Client is the default client of Elasticsearch, it provides a straight forward replacement for the TransportClient
as it accepts and returns
the very same request/response objects and therefore depends on the Elasticsearch core project.
Asynchronous calls are operated upon a client managed thread pool and require a callback to be notified when the request is done.
@Configuration
public class RestClientConfig extends AbstractElasticsearchConfiguration {
@Override
@Bean
public RestHighLevelClient elasticsearchClient() {
final ClientConfiguration clientConfiguration = ClientConfiguration.builder() (1)
.connectedTo("localhost:9200")
.build();
return RestClients.create(clientConfiguration).rest(); (2)
}
}
// ...
@Autowired
RestHighLevelClient highLevelClient;
RestClient lowLevelClient = highLevelClient.lowLevelClient(); (3)
// ...
IndexRequest request = new IndexRequest("spring-data", "elasticsearch", randomID())
.source(singletonMap("feature", "high-level-rest-client"))
.setRefreshPolicy(IMMEDIATE);
IndexResponse response = highLevelClient.index(request);
1 | Use the builder to provide cluster addresses, set default HttpHeaders or enable SSL. |
2 | Create the RestHighLevelClient. |
3 | It is also possible to obtain the lowLevelRest() client. |
5.3. Reactive Client
The ReactiveElasticsearchClient
is a non official driver based on WebClient
.
It uses the request/response objects provided by the Elasticsearch core project.
Calls are directly operated on the reactive stack, not wrapping async (thread pool bound) responses into reactive types.
static class Config {
@Bean
ReactiveElasticsearchClient client() {
ClientConfiguration clientConfiguration = ClientConfiguration.builder() (1)
.connectedTo("localhost:9200", "localhost:9291")
.withWebClientConfigurer(webClient -> { (2)
ExchangeStrategies exchangeStrategies = ExchangeStrategies.builder()
.codecs(configurer -> configurer.defaultCodecs()
.maxInMemorySize(-1))
.build();
return webClient.mutate().exchangeStrategies(exchangeStrategies).build();
})
.build();
return ReactiveRestClients.create(clientConfiguration);
}
}
// ...
Mono<IndexResponse> response = client.index(request ->
request.index("spring-data")
.type("elasticsearch")
.id(randomID())
.source(singletonMap("feature", "reactive-client"))
.setRefreshPolicy(IMMEDIATE);
);
1 | Use the builder to provide cluster addresses, set default HttpHeaders or enable SSL. |
2 | when configuring a reactive client, the withWebClientConfigurer hook can be used to customize the WebClient. |
The ReactiveClient response, especially for search operations, is bound to the from (offset) & size (limit) options of the request.
|
5.4. Client Configuration
Client behaviour can be changed via the ClientConfiguration
that allows to set options for SSL, connect and socket timeouts, headers and other parameters.
HttpHeaders httpHeaders = new HttpHeaders();
httpHeaders.add("some-header", "on every request") (1)
ClientConfiguration clientConfiguration = ClientConfiguration.builder()
.connectedTo("localhost:9200", "localhost:9291") (2)
.useSsl() (3)
.withProxy("localhost:8888") (4)
.withPathPrefix("ela") (5)
.withConnectTimeout(Duration.ofSeconds(5)) (6)
.withSocketTimeout(Duration.ofSeconds(3)) (7)
.withDefaultHeaders(defaultHeaders) (8)
.withBasicAuth(username, password) (9)
.withHeaders(() -> { (10)
HttpHeaders headers = new HttpHeaders();
headers.add("currentTime", LocalDateTime.now().format(DateTimeFormatter.ISO_LOCAL_DATE_TIME));
return headers;
})
. // ... other options
.build();
1 | Define default headers, if they need to be customized |
2 | Use the builder to provide cluster addresses, set default HttpHeaders or enable SSL. |
3 | Optionally enable SSL. |
4 | Optionally set a proxy. |
5 | Optionally set a path prefix, mostly used when different clusters a behind some reverse proxy. |
6 | Set the connection timeout. Default is 10 sec. |
7 | Set the socket timeout. Default is 5 sec. |
8 | Optionally set headers. |
9 | Add basic authentication. |
10 | A Supplier<Header> function can be specified which is called every time before a request is sent to Elasticsearch - here, as an example, the current time is written in a header. |
Adding a Header supplier as shown in above example allows to inject headers that may change over the time, like authentication JWT tokens. If this is used in the reactive setup, the supplier function must not block! |
5.5. Client Logging
To see what is actually sent to and received from the server Request
/ Response
logging on the transport level needs
to be turned on as outlined in the snippet below.
<logger name="org.springframework.data.elasticsearch.client.WIRE" level="trace"/>
The above applies to both the RestHighLevelClient and ReactiveElasticsearchClient when obtained via RestClients respectively ReactiveRestClients , is not available for the TransportClient .
|
6. Elasticsearch Object Mapping
Spring Data Elasticsearch Object Mapping is the process that maps a Java object - the domain entity - into the JSON representation that is stored in Elasticsearch and back.
Earlier versions of Spring Data Elasticsearch used a Jackson based conversion, Spring Data Elasticsearch 3.2.x introduced the Meta Model Object Mapping.
As of version 4.0 only the Meta Object Mapping is used, the Jackson based mapper is not available anymore and the MappingElasticsearchConverter
is used.
The main reasons for the removal of the Jackson based mapper are:
-
Custom mappings of fields needed to be done with annotations like
@JsonFormat
or@JsonInclude
. This often caused problems when the same object was used in different JSON based datastores or sent over a JSON based API. -
Custom field types and formats also need to be stored into the Elasticsearch index mappings. The Jackson based annotations did not fully provide all the information that is necessary to represent the types of Elasticsearch.
-
Fields must be mapped not only when converting from and to entities, but also in query argument, returned data and on other places.
Using the MappingElasticsearchConverter
now covers all these cases.
6.1. Meta Model Object Mapping
The Metamodel based approach uses domain type information for reading/writing from/to Elasticsearch.
This allows to register Converter
instances for specific domain type mapping.
6.1.1. Mapping Annotation Overview
The MappingElasticsearchConverter
uses metadata to drive the mapping of objects to documents.
The metadata is taken from the entity’s properties which can be annotated.
The following annotations are available:
-
@Document
: Applied at the class level to indicate this class is a candidate for mapping to the database. The most important attributes are:-
indexName
: the name of the index to store this entity in. This can contain a SpEL template expression like"log-#{T(java.time.LocalDate).now().toString()}"
-
type
: the mapping type. If not set, the lowercased simple name of the class is used. (deprecated since version 4.0) -
shards
: the number of shards for the index. -
replicas
: the number of replicas for the index. -
refreshIntervall
: Refresh interval for the index. Used for index creation. Default value is "1s". -
indexStoreType
: Index storage type for the index. Used for index creation. Default value is "fs". -
createIndex
: flag whether to create an index on repository bootstrapping. Default value is true. See Automatic creation of indices with the corresponding mapping -
versionType
: Configuration of version management. Default value is EXTERNAL.
-
-
@Id
: Applied at the field level to mark the field used for identity purpose. -
@Transient
: By default all fields are mapped to the document when it is stored or retrieved, this annotation excludes the field. -
@PersistenceConstructor
: Marks a given constructor - even a package protected one - to use when instantiating the object from the database. Constructor arguments are mapped by name to the key values in the retrieved Document. -
@Field
: Applied at the field level and defines properties of the field, most of the attributes map to the respective Elasticsearch Mapping definitions (the following list is not complete, check the annotation Javadoc for a complete reference):-
name
: The name of the field as it will be represented in the Elasticsearch document, if not set, the Java field name is used. -
type
: the field type, can be one of Text, Keyword, Long, Integer, Short, Byte, Double, Float, Half_Float, Scaled_Float, Date, Date_Nanos, Boolean, Binary, Integer_Range, Float_Range, Long_Range, Double_Range, Date_Range, Ip_Range, Object, Nested, Ip, TokenCount, Percolator, Flattened, Search_As_You_Type. See Elasticsearch Mapping Types -
format
andpattern
definitions for the Date type.format
must be defined for date types. -
store
: Flag whether the original field value should be store in Elasticsearch, default value is false. -
analyzer
,searchAnalyzer
,normalizer
for specifying custom analyzers and normalizer.
-
-
@GeoPoint
: marks a field as geo_point datatype. Can be omitted if the field is an instance of theGeoPoint
class.
Properties that derive from TemporalAccessor must either have a @Field annotation of type FieldType.Date or a custom converter must be registered for this type.If you are using a custom date format, you need to use uuuu for the year instead of yyyy. This is due to a change in Elasticsearch 7. |
The mapping metadata infrastructure is defined in a separate spring-data-commons project that is technology agnostic.
6.1.2. Mapping Rules
Type Hints
Mapping uses type hints embedded in the document sent to the server to allow generic type mapping.
Those type hints are represented as _class
attributes within the document and are written for each aggregate root.
public class Person { (1)
@Id String id;
String firstname;
String lastname;
}
{
"_class" : "com.example.Person", (1)
"id" : "cb7bef",
"firstname" : "Sarah",
"lastname" : "Connor"
}
1 | By default the domain types class name is used for the type hint. |
Type hints can be configured to hold custom information.
Use the @TypeAlias
annotation to do so.
Make sure to add types with @TypeAlias to the initial entity set (AbstractElasticsearchConfiguration#getInitialEntitySet ) to already have entity information available when first reading data from the store.
|
@TypeAlias("human") (1)
public class Person {
@Id String id;
// ...
}
{
"_class" : "human", (1)
"id" : ...
}
1 | The configured alias is used when writing the entity. |
Type hints will not be written for nested Objects unless the properties type is Object , an interface or the actual value type does not match the properties declaration.
|
Geospatial Types
Geospatial types like Point
& GeoPoint
are converted into lat/lon pairs.
public class Address {
String city, street;
Point location;
}
{
"city" : "Los Angeles",
"street" : "2800 East Observatory Road",
"location" : { "lat" : 34.118347, "lon" : -118.3026284 }
}
GeoJson Types
Spring Data Elasticsearch supports the GeoJson types by providing an interface GeoJson
and implementations for the different geometries.
They are mapped to Elasticsearch documents according to the GeoJson specification.
The corresponding properties of the entity are specified in the index mappings as geo_shape
when the index mappings is written. (check the Elasticsearch documentation as well)
public class Address {
String city, street;
GeoJsonPoint location;
}
{
"city": "Los Angeles",
"street": "2800 East Observatory Road",
"location": {
"type": "Point",
"coordinates": [-118.3026284, 34.118347]
}
}
The following GeoJson types are implemented:
-
GeoJsonPoint
-
GeoJsonMultiPoint
-
GeoJsonLineString
-
GeoJsonMultiLineString
-
GeoJsonPolygon
-
GeoJsonMultiPolygon
-
GeoJsonGeometryCollection
Collections
For values inside Collections apply the same mapping rules as for aggregate roots when it comes to type hints and Custom Conversions.
public class Person {
// ...
List<Person> friends;
}
{
// ...
"friends" : [ { "firstname" : "Kyle", "lastname" : "Reese" } ]
}
Maps
For values inside Maps apply the same mapping rules as for aggregate roots when it comes to type hints and Custom Conversions. However the Map key needs to a String to be processed by Elasticsearch.
public class Person {
// ...
Map<String, Address> knownLocations;
}
{
// ...
"knownLocations" : {
"arrivedAt" : {
"city" : "Los Angeles",
"street" : "2800 East Observatory Road",
"location" : { "lat" : 34.118347, "lon" : -118.3026284 }
}
}
}
6.1.3. Custom Conversions
Looking at the Configuration
from the previous section ElasticsearchCustomConversions
allows registering specific rules for mapping domain and simple types.
@Configuration
public class Config extends AbstractElasticsearchConfiguration {
@Override
public RestHighLevelClient elasticsearchClient() {
return RestClients.create(ClientConfiguration.create("localhost:9200")).rest();
}
@Bean
@Override
public ElasticsearchCustomConversions elasticsearchCustomConversions() {
return new ElasticsearchCustomConversions(
Arrays.asList(new AddressToMap(), new MapToAddress())); (1)
}
@WritingConverter (2)
static class AddressToMap implements Converter<Address, Map<String, Object>> {
@Override
public Map<String, Object> convert(Address source) {
LinkedHashMap<String, Object> target = new LinkedHashMap<>();
target.put("ciudad", source.getCity());
// ...
return target;
}
}
@ReadingConverter (3)
static class MapToAddress implements Converter<Map<String, Object>, Address> {
@Override
public Address convert(Map<String, Object> source) {
// ...
return address;
}
}
}
{
"ciudad" : "Los Angeles",
"calle" : "2800 East Observatory Road",
"localidad" : { "lat" : 34.118347, "lon" : -118.3026284 }
}
1 | Add Converter implementations. |
2 | Set up the Converter used for writing DomainType to Elasticsearch. |
3 | Set up the Converter used for reading DomainType from search result. |
7. Elasticsearch Operations
Spring Data Elasticsearch uses several interfaces to define the operations that can be called against an Elasticsearch index (for a description of the reactive interfaces see Reactive Elasticsearch Operations).
-
IndexOperations
defines actions on index level like creating or deleting an index. -
DocumentOperations
defines actions to store, update and retrieve entities based on their id. -
SearchOperations
define the actions to search for multiple entities using queries -
ElasticsearchOperations
combines theDocumentOperations
andSearchOperations
interfaces.
These interfaces correspond to the structuring of the Elasticsearch API.
The default implementations of the interfaces offer:
-
index management functionality.
-
Read/Write mapping support for domain types.
-
A rich query and criteria api.
-
Resource management and Exception translation.
Index management and automatic creation of indices and mappings.
The None of these operations are done automatically by the implementations of There is support for automatic creation of indices and writing the mappings when using Spring Data Elasticsearch repositories, see Automatic creation of indices with the corresponding mapping |
7.1. ElasticsearchTemplate
Usage of the ElasticsearchTemplate is deprecated as of version 4.0, use ElasticsearchRestTemplate instead. |
The ElasticsearchTemplate
is an implementation of the ElasticsearchOperations
interface using the Transport Client.
@Configuration
public class TransportClientConfig extends ElasticsearchConfigurationSupport {
@Bean
public Client elasticsearchClient() throws UnknownHostException { (1)
Settings settings = Settings.builder().put("cluster.name", "elasticsearch").build();
TransportClient client = new PreBuiltTransportClient(settings);
client.addTransportAddress(new TransportAddress(InetAddress.getByName("127.0.0.1"), 9300));
return client;
}
@Bean(name = {"elasticsearchOperations", "elasticsearchTemplate"})
public ElasticsearchTemplate elasticsearchTemplate() throws UnknownHostException { (2)
return new ElasticsearchTemplate(elasticsearchClient());
}
}
1 | Setting up the Transport Client. Deprecated as of version 4.0. |
2 | Creating the ElasticsearchTemplate bean, offering both names, elasticsearchOperations and elasticsearchTemplate. |
7.2. ElasticsearchRestTemplate
The ElasticsearchRestTemplate
is an implementation of the ElasticsearchOperations
interface using the High Level REST Client.
@Configuration
public class RestClientConfig extends AbstractElasticsearchConfiguration {
@Override
public RestHighLevelClient elasticsearchClient() { (1)
return RestClients.create(ClientConfiguration.localhost()).rest();
}
// no special bean creation needed (2)
}
1 | Setting up the High Level REST Client. |
2 | The base class AbstractElasticsearchConfiguration already provides the elasticsearchTemplate bean. |
7.3. Usage examples
As both ElasticsearchTemplate
and ElasticsearchRestTemplate
implement the ElasticsearchOperations
interface, the code to use them is not different.
The example shows how to use an injected ElasticsearchOperations
instance in a Spring REST controller.
The decision, if this is using the TransportClient
or the RestClient
is made by providing the corresponding Bean with one of the configurations shown above.
@RestController
@RequestMapping("/")
public class TestController {
private ElasticsearchOperations elasticsearchOperations;
public TestController(ElasticsearchOperations elasticsearchOperations) { (1)
this.elasticsearchOperations = elasticsearchOperations;
}
@PostMapping("/person")
public String save(@RequestBody Person person) { (2)
IndexQuery indexQuery = new IndexQueryBuilder()
.withId(person.getId().toString())
.withObject(person)
.build();
String documentId = elasticsearchOperations.index(indexQuery);
return documentId;
}
@GetMapping("/person/{id}")
public Person findById(@PathVariable("id") Long id) { (3)
Person person = elasticsearchOperations
.queryForObject(GetQuery.getById(id.toString()), Person.class);
return person;
}
}
1 | Let Spring inject the provided ElasticsearchOperations bean in the constructor. |
2 | Store some entity in the Elasticsearch cluster. |
3 | Retrieve the entity with a query by id. |
To see the full possibilities of ElasticsearchOperations
please refer to the API documentation.
7.4. Reactive Elasticsearch Operations
ReactiveElasticsearchOperations
is the gateway to executing high level commands against an Elasticsearch cluster using the ReactiveElasticsearchClient
.
The ReactiveElasticsearchTemplate
is the default implementation of ReactiveElasticsearchOperations
.
7.4.1. Reactive Elasticsearch Template
To get started the ReactiveElasticsearchTemplate
needs to know about the actual client to work with.
Please see Reactive Client for details on the client.
Reactive Template Configuration
The easiest way of setting up the ReactiveElasticsearchTemplate
is via AbstractReactiveElasticsearchConfiguration
providing
dedicated configuration method hooks for base package
, the initial entity set
etc.
@Configuration
public class Config extends AbstractReactiveElasticsearchConfiguration {
@Bean (1)
@Override
public ReactiveElasticsearchClient reactiveElasticsearchClient() {
// ...
}
}
1 | Configure the client to use. This can be done by ReactiveRestClients or directly via DefaultReactiveElasticsearchClient . |
If applicable set default HttpHeaders via the ClientConfiguration of the ReactiveElasticsearchClient . See Client Configuration.
|
If needed the ReactiveElasticsearchTemplate can be configured with default RefreshPolicy and IndicesOptions that get applied to the related requests by overriding the defaults of refreshPolicy() and indicesOptions() .
|
However one might want to be more in control over the actual components and use a more verbose approach.
@Configuration
public class Config {
@Bean (1)
public ReactiveElasticsearchClient reactiveElasticsearchClient() {
// ...
}
@Bean (2)
public ElasticsearchConverter elasticsearchConverter() {
return new MappingElasticsearchConverter(elasticsearchMappingContext());
}
@Bean (3)
public SimpleElasticsearchMappingContext elasticsearchMappingContext() {
return new SimpleElasticsearchMappingContext();
}
@Bean (4)
public ReactiveElasticsearchOperations reactiveElasticsearchOperations() {
return new ReactiveElasticsearchTemplate(reactiveElasticsearchClient(), elasticsearchConverter());
}
}
1 | Configure the client to use. This can be done by ReactiveRestClients or directly via DefaultReactiveElasticsearchClient . |
2 | Set up the ElasticsearchConverter used for domain type mapping utilizing metadata provided by the mapping context. |
3 | The Elasticsearch specific mapping context for domain type metadata. |
4 | The actual template based on the client and conversion infrastructure. |
Reactive Template Usage
ReactiveElasticsearchTemplate
lets you save, find and delete your domain objects and map those objects to documents stored in Elasticsearch.
Consider the following:
@Document(indexName = "marvel")
public class Person {
private @Id String id;
private String name;
private int age;
// Getter/Setter omitted...
}
template.save(new Person("Bruce Banner", 42)) (1)
.doOnNext(System.out::println)
.flatMap(person -> template.findById(person.id, Person.class)) (2)
.doOnNext(System.out::println)
.flatMap(person -> template.delete(person)) (3)
.doOnNext(System.out::println)
.flatMap(id -> template.count(Person.class)) (4)
.doOnNext(System.out::println)
.subscribe(); (5)
The above outputs the following sequence on the console.
> Person(id=QjWCWWcBXiLAnp77ksfR, name=Bruce Banner, age=42)
> Person(id=QjWCWWcBXiLAnp77ksfR, name=Bruce Banner, age=42)
> QjWCWWcBXiLAnp77ksfR
> 0
1 | Insert a new Person document into the marvel index under type characters. The id is generated on server side and set into the instance returned. |
2 | Lookup the Person with matching id in the marvel index under type characters. |
3 | Delete the Person with matching id , extracted from the given instance, in the marvel index under type characters. |
4 | Count the total number of documents in the marvel index under type characters. |
5 | Don’t forget to subscribe(). |
7.5. Search Result Types
When a document is retrieved with the methods of the DocumentOperations
interface, just the found entity will be returned.
When searching with the methods of the SearchOperations
interface, additional information is available for each entity, for example the score or the sortValues of the found entity.
In order to return this information, each entity is wrapped in a SearchHit
object that contains this entity-specific additional information.
These SearchHit
objects themselves are returned within a SearchHits
object which additionally contains informations about the whole search like the maxScore or requested aggregations.
The following classes and interfaces are now available:
Contains the following information:
-
Id
-
Score
-
Sort Values
-
Highlight fields
-
Inner hits (this is an embedded
SearchHits
object containing eventually returned inner hits) -
The retrieved entity of type <T>
Contains the following information:
-
Number of total hits
-
Total hits relation
-
Maximum score
-
A list of
SearchHit<T>
objects -
Returned aggregations
Defines a Spring Data Page
that contains a SearchHits<T>
element and can be used for paging access using repository methods.
Returned by the low level scroll API functions in ElasticsearchRestTemplate
, it enriches a SearchHits<T>
with the Elasticsearch scroll id.
An Iterator returned by the streaming functions of the SearchOperations
interface.
7.6. Queries
Almost all of the methods defined in the SearchOperations
and ReactiveSearchOperations
interface take a Query
parameter that defines the query to execute for searching. Query
is an interface and Spring Data Elasticsearch provides three implementations: CriteriaQuery
, StringQuery
and NativeSearchQuery
.
7.6.1. CriteriaQuery
CriteriaQuery
based queries allow the creation of queries to search for data without knowing the syntax or basics of Elasticsearch queries. They allow the user to build queries by simply chaining and combining Criteria
objects that specifiy the criteria the searched documents must fulfill.
when talking about AND or OR when combining criteria keep in mind, that in Elasticsearch AND are converted to a must condition and OR to a should |
Criteria
and their usage are best explained by example
(let’s assume we have a Book
entity with a price
property):
Criteria criteria = new Criteria("price").is(42.0);
Query query = new CriteriaQuery(criteria);
Conditions for the same field can be chained, they will be combined with a logical AND:
Criteria criteria = new Criteria("price").greaterThan(42.0).lessThan(34.0L);
Query query = new CriteriaQuery(criteria);
When chaining Criteria
, by default a AND logic is used:
Criteria criteria = new Criteria("lastname").is("Miller") (1)
.and("firstname").is("James") (2)
Query query = new CriteriaQuery(criteria);
1 | the first Criteria |
2 | the and() creates a new Criteria and chaines it to the first one. |
If you want to create nested queries, you need to use subqueries for this. Let’s assume we want to find all persons with a last name of Miller and a first name of either Jack or John:
Criteria miller = new Criteria("lastName").is("Miller") (1)
.subCriteria( (2)
new Criteria().or("firstName").is("John") (3)
.or("firstName").is("Jack") (4)
);
Query query = new CriteriaQuery(criteria);
1 | create a first Criteria for the last name |
2 | this is combined with AND to a subCriteria |
3 | This sub Criteria is an OR combination for the first name John |
4 | and the first name Jack |
Please refer to the API documentation of the Criteria
class for a complete overview of the different available operations.
7.6.2. StringQuery
This class takes an Elasticsearch query as JSON String. The following code shows a query that searches for persons having the first name "Jack":
Query query = new SearchQuery("{ \"match\": { \"firstname\": { \"query\": \"Jack\" } } } ");
SearchHits<Person> searchHits = operations.search(query, Person.class);
Using StringQuery
may be appropriate if you already have an Elasticsearch query to use.
7.6.3. NativeSearchQuery
NativeSearchQuery
is the class to use when you have a complex query, or a query that cannot be expressed by using the Criteria
API, for example when building queries and using aggregates.
It allows to use all the different QueryBuilder
implementations from the Elasticsearch library therefore named "native".
The following code shows how to search for persons with a given firstname and for the found documents have a terms aggregation that counts the number of occurences of the lastnames for these persons:
Query query = new NativeSearchQueryBuilder()
.addAggregation(terms("lastnames").field("lastname").size(10)) //
.withQuery(QueryBuilders.matchQuery("firstname", firstName))
.build();
SearchHits<Person> searchHits = operations.search(query, Person.class);
8. Elasticsearch Repositories
This chapter includes details of the Elasticsearch repository implementation.
Book
entity@Document(indexName="books")
class Book {
@Id
private String id;
@Field(type = FieldType.text)
private String name;
@Field(type = FieldType.text)
private String summary;
@Field(type = FieldType.Integer)
private Integer price;
// getter/setter ...
}
8.1. Automatic creation of indices with the corresponding mapping
The @Document
annotation has an argument createIndex
. If this argument is set to true - which is the default value - Spring Data Elasticsearch will during bootstrapping the repository support on application startup check if the index defined by the @Document
annotation exists.
If it does not exist, the index will be created and the mappings derived from the entity’s annotations (see Elasticsearch Object Mapping) will be written to the newly created index.
8.2. Query methods
8.2.1. Query lookup strategies
The Elasticsearch module supports all basic query building feature as string queries, native search queries, criteria based queries or have it being derived from the method name.
Declared queries
Deriving the query from the method name is not always sufficient and/or may result in unreadable method names.
In this case one might make use of the @Query
annotation (see Using @Query Annotation ).
8.2.2. Query creation
Generally the query creation mechanism for Elasticsearch works as described in Query Methods. Here’s a short example of what a Elasticsearch query method translates into:
interface BookRepository extends Repository<Book, String> {
List<Book> findByNameAndPrice(String name, Integer price);
}
The method name above will be translated into the following Elasticsearch json query
{
"query": {
"bool" : {
"must" : [
{ "query_string" : { "query" : "?", "fields" : [ "name" ] } },
{ "query_string" : { "query" : "?", "fields" : [ "price" ] } }
]
}
}
}
A list of supported keywords for Elasticsearch is shown below.
Keyword | Sample | Elasticsearch Query String |
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Methods names to build Geo-shape queries taking GeoJson parameters are not supported.
Use ElasticsearchOperations with CriteriaQuery in a custom repository implementation if you need to have such a function in a repository.
|
8.2.3. Method return types
Repository methods can be defined to have the following return types for returning multiple Elements:
-
List<T>
-
Stream<T>
-
SearchHits<T>
-
List<SearchHit<T>>
-
Stream<SearchHit<T>>
-
SearchPage<T>
8.2.4. Using @Query Annotation
@Query
annotation.interface BookRepository extends ElasticsearchRepository<Book, String> {
@Query("{\"match\": {\"name\": {\"query\": \"?0\"}}}")
Page<Book> findByName(String name,Pageable pageable);
}
The String that is set as the annotation argument must be a valid Elasticsearch JSON query. It will be sent to Easticsearch as value of the query element; if for example the function is called with the parameter John, it would produce the following query body:
{
"query": {
"match": {
"name": {
"query": "John"
}
}
}
}
8.3. Reactive Elasticsearch Repositories
Reactive Elasticsearch repository support builds on the core repository support explained in Working with Spring Data Repositories utilizing operations provided via Reactive Elasticsearch Operations executed by a Reactive Client.
Spring Data Elasticsearch reactive repository support uses Project Reactor as its reactive composition library of choice.
There are 3 main interfaces to be used:
-
ReactiveRepository
-
ReactiveCrudRepository
-
ReactiveSortingRepository
8.3.1. Usage
To access domain objects stored in a Elasticsearch using a Repository
, just create an interface for it.
Before you can actually go on and do that you will need an entity.
Person
entitypublic class Person {
@Id
private String id;
private String firstname;
private String lastname;
private Address address;
// … getters and setters omitted
}
Please note that the id property needs to be of type String .
|
interface ReactivePersonRepository extends ReactiveSortingRepository<Person, String> {
Flux<Person> findByFirstname(String firstname); (1)
Flux<Person> findByFirstname(Publisher<String> firstname); (2)
Flux<Person> findByFirstnameOrderByLastname(String firstname); (3)
Flux<Person> findByFirstname(String firstname, Sort sort); (4)
Flux<Person> findByFirstname(String firstname, Pageable page); (5)
Mono<Person> findByFirstnameAndLastname(String firstname, String lastname); (6)
Mono<Person> findFirstByLastname(String lastname); (7)
@Query("{ \"bool\" : { \"must\" : { \"term\" : { \"lastname\" : \"?0\" } } } }")
Flux<Person> findByLastname(String lastname); (8)
Mono<Long> countByFirstname(String firstname) (9)
Mono<Boolean> existsByFirstname(String firstname) (10)
Mono<Long> deleteByFirstname(String firstname) (11)
}
1 | The method shows a query for all people with the given lastname . |
2 | Finder method awaiting input from Publisher to bind parameter value for firstname . |
3 | Finder method ordering matching documents by lastname . |
4 | Finder method ordering matching documents by the expression defined via the Sort parameter. |
5 | Use Pageable to pass offset and sorting parameters to the database. |
6 | Finder method concating criteria using And / Or keywords. |
7 | Find the first matching entity. |
8 | The method shows a query for all people with the given lastname looked up by running the annotated @Query with given
parameters. |
9 | Count all entities with matching firstname . |
10 | Check if at least one entity with matching firstname exists. |
11 | Delete all entites with matching firstname . |
8.3.2. Configuration
For Java configuration, use the @EnableReactiveElasticsearchRepositories
annotation. If no base package is configured,
the infrastructure scans the package of the annotated configuration class.
The following listing shows how to use Java configuration for a repository:
@Configuration
@EnableReactiveElasticsearchRepositories
public class Config extends AbstractReactiveElasticsearchConfiguration {
@Override
public ReactiveElasticsearchClient reactiveElasticsearchClient() {
return ReactiveRestClients.create(ClientConfiguration.localhost());
}
}
Because the repository from the previous example extends ReactiveSortingRepository
, all CRUD operations are available
as well as methods for sorted access to the entities. Working with the repository instance is a matter of dependency
injecting it into a client, as the following example shows:
public class PersonRepositoryTests {
@Autowired ReactivePersonRepository repository;
@Test
public void sortsElementsCorrectly() {
Flux<Person> persons = repository.findAll(Sort.by(new Order(ASC, "lastname")));
// ...
}
}
8.4. Annotations for repository methods
8.4.1. @Highlight
The @Highlight
annotation on a repository method defines for which fields of the returned entity highlighting should be included. To search for some text in a Book
's name or summary and have the found data highlighted, the following repository method can be used:
interface BookRepository extends Repository<Book, String> {
@Highlight(fields = {
@HighlightField(name = "name"),
@HighlightField(name = "summary")
})
List<SearchHit<Book>> findByNameOrSummary(String text, String summary);
}
It is possible to define multiple fields to be highlighted like above, and both the @Highlight
and the @HighlightField
annotation can further be customized with a @HighlightParameters
annotation. Check the Javadocs for the possible configuration options.
In the search results the highlight data can be retrieved from the SearchHit
class.
8.5. Annotation based configuration
The Spring Data Elasticsearch repositories support can be activated using an annotation through JavaConfig.
@Configuration
@EnableElasticsearchRepositories( (1)
basePackages = "org.springframework.data.elasticsearch.repositories"
)
static class Config {
@Bean
public ElasticsearchOperations elasticsearchTemplate() { (2)
// ...
}
}
class ProductService {
private ProductRepository repository; (3)
public ProductService(ProductRepository repository) {
this.repository = repository;
}
public Page<Product> findAvailableBookByName(String name, Pageable pageable) {
return repository.findByAvailableTrueAndNameStartingWith(name, pageable);
}
}
1 | The EnableElasticsearchRepositories annotation activates the Repository support.
If no base package is configured, it will use the one of the configuration class it is put on. |
2 | Provide a Bean named elasticsearchTemplate of type ElasticsearchOperations by using one of the configurations shown in the Elasticsearch Operations chapter. |
3 | Let Spring inject the Repository bean into your class. |
8.6. Elasticsearch Repositories using CDI
The Spring Data Elasticsearch repositories can also be set up using CDI functionality.
class ElasticsearchTemplateProducer {
@Produces
@ApplicationScoped
public ElasticsearchOperations createElasticsearchTemplate() {
// ... (1)
}
}
class ProductService {
private ProductRepository repository; (2)
public Page<Product> findAvailableBookByName(String name, Pageable pageable) {
return repository.findByAvailableTrueAndNameStartingWith(name, pageable);
}
@Inject
public void setRepository(ProductRepository repository) {
this.repository = repository;
}
}
1 | Create a component by using the same calls as are used in the Elasticsearch Operations chapter. |
2 | Let the CDI framework inject the Repository into your class. |
8.7. Spring Namespace
The Spring Data Elasticsearch module contains a custom namespace allowing definition of repository beans as well as elements for instantiating a ElasticsearchServer
.
Using the repositories
element looks up Spring Data repositories as described in Creating Repository Instances .
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:elasticsearch="http://www.springframework.org/schema/data/elasticsearch"
xsi:schemaLocation="http://www.springframework.org/schema/beans
https://www.springframework.org/schema/beans/spring-beans-3.1.xsd
http://www.springframework.org/schema/data/elasticsearch
https://www.springframework.org/schema/data/elasticsearch/spring-elasticsearch-1.0.xsd">
<elasticsearch:repositories base-package="com.acme.repositories" />
</beans>
Using the Transport Client
or Rest Client
element registers an instance of Elasticsearch Server
in the context.
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:elasticsearch="http://www.springframework.org/schema/data/elasticsearch"
xsi:schemaLocation="http://www.springframework.org/schema/beans
https://www.springframework.org/schema/beans/spring-beans-3.1.xsd
http://www.springframework.org/schema/data/elasticsearch
https://www.springframework.org/schema/data/elasticsearch/spring-elasticsearch-1.0.xsd">
<elasticsearch:transport-client id="client" cluster-nodes="localhost:9300,someip:9300" />
</beans>
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:elasticsearch="http://www.springframework.org/schema/data/elasticsearch"
xsi:schemaLocation="http://www.springframework.org/schema/data/elasticsearch
https://www.springframework.org/schema/data/elasticsearch/spring-elasticsearch.xsd
http://www.springframework.org/schema/beans
https://www.springframework.org/schema/beans/spring-beans.xsd">
<elasticsearch:rest-client id="restClient" hosts="http://localhost:9200">
</beans>
9. Auditing
9.1. Basics
Spring Data provides sophisticated support to transparently keep track of who created or changed an entity and when the change happened. To benefit from that functionality, you have to equip your entity classes with auditing metadata that can be defined either using annotations or by implementing an interface.
9.1.1. Annotation-based Auditing Metadata
We provide @CreatedBy
and @LastModifiedBy
to capture the user who created or modified the entity as well as @CreatedDate
and @LastModifiedDate
to capture when the change happened.
class Customer {
@CreatedBy
private User user;
@CreatedDate
private DateTime createdDate;
// … further properties omitted
}
As you can see, the annotations can be applied selectively, depending on which information you want to capture. The annotations capturing when changes were made can be used on properties of type Joda-Time, DateTime
, legacy Java Date
and Calendar
, JDK8 date and time types, and long
or Long
.
9.1.2. Interface-based Auditing Metadata
In case you do not want to use annotations to define auditing metadata, you can let your domain class implement the Auditable
interface. It exposes setter methods for all of the auditing properties.
There is also a convenience base class, AbstractAuditable
, which you can extend to avoid the need to manually implement the interface methods. Doing so increases the coupling of your domain classes to Spring Data, which might be something you want to avoid. Usually, the annotation-based way of defining auditing metadata is preferred as it is less invasive and more flexible.
9.1.3. AuditorAware
In case you use either @CreatedBy
or @LastModifiedBy
, the auditing infrastructure somehow needs to become aware of the current principal. To do so, we provide an AuditorAware<T>
SPI interface that you have to implement to tell the infrastructure who the current user or system interacting with the application is. The generic type T
defines what type the properties annotated with @CreatedBy
or @LastModifiedBy
have to be.
The following example shows an implementation of the interface that uses Spring Security’s Authentication
object:
AuditorAware
based on Spring Securityclass SpringSecurityAuditorAware implements AuditorAware<User> {
@Override
public Optional<User> getCurrentAuditor() {
return Optional.ofNullable(SecurityContextHolder.getContext())
.map(SecurityContext::getAuthentication)
.filter(Authentication::isAuthenticated)
.map(Authentication::getPrincipal)
.map(User.class::cast);
}
}
The implementation accesses the Authentication
object provided by Spring Security and looks up the custom UserDetails
instance that you have created in your UserDetailsService
implementation. We assume here that you are exposing the domain user through the UserDetails
implementation but that, based on the Authentication
found, you could also look it up from anywhere.
9.1.4. ReactiveAuditorAware
When using reactive infrastructure you might want to make use of contextual information to provide @CreatedBy
or @LastModifiedBy
information.
We provide an ReactiveAuditorAware<T>
SPI interface that you have to implement to tell the infrastructure who the current user or system interacting with the application is. The generic type T
defines what type the properties annotated with @CreatedBy
or @LastModifiedBy
have to be.
The following example shows an implementation of the interface that uses reactive Spring Security’s Authentication
object:
ReactiveAuditorAware
based on Spring Securityclass SpringSecurityAuditorAware implements ReactiveAuditorAware<User> {
@Override
public Mono<User> getCurrentAuditor() {
return ReactiveSecurityContextHolder.getContext()
.map(SecurityContext::getAuthentication)
.filter(Authentication::isAuthenticated)
.map(Authentication::getPrincipal)
.map(User.class::cast);
}
}
The implementation accesses the Authentication
object provided by Spring Security and looks up the custom UserDetails
instance that you have created in your UserDetailsService
implementation. We assume here that you are exposing the domain user through the UserDetails
implementation but that, based on the Authentication
found, you could also look it up from anywhere.
9.2. Elasticsearch Auditing
9.2.1. Preparing entities
In order for the auditing code to be able to decide whether an entity instance is new, the entity must implement the Persistable<ID>
interface which is defined as follows:
package org.springframework.data.domain;
import org.springframework.lang.Nullable;
public interface Persistable<ID> {
@Nullable
ID getId();
boolean isNew();
}
As the existence of an Id is not a sufficient criterion to determine if an enitity is new in Elasticsearch, additional information is necessary. One way is to use the creation-relevant auditing fields for this decision:
A Person
entity might look as follows - omitting getter and setter methods for brevity:
@Document(indexName = "person")
public class Person implements Persistable<Long> {
@Id private Long id;
private String lastName;
private String firstName;
@Field(type = FieldType.Date, format = DateFormat.basic_date_time)
private Instant createdDate;
private String createdBy
@Field(type = FieldType.Date, format = DateFormat.basic_date_time)
private Instant lastModifiedDate;
private String lastModifiedBy;
public Long getId() { (1)
return id;
}
@Override
public boolean isNew() {
return id == null || (createdDate == null && createdBy == null); (2)
}
}
1 | the getter is the required implementation from the interface |
2 | an object is new if it either has no id or none of fields containing creation attributes are set. |
9.2.2. Activating auditing
After the entities have been set up and providing the AuditorAware
- or ReactiveAuditorAware
- the Auditing must be activated by setting the @EnableElasticsearchAuditing
on a configuration class:
@Configuration
@EnableElasticsearchRepositories
@EnableElasticsearchAuditing
class MyConfiguration {
// configuration code
}
When using the reactive stack this must be:
@Configuration
@EnableReactiveElasticsearchRepositories
@EnableReactiveElasticsearchAuditing
class MyConfiguration {
// configuration code
}
If your code contains more than one AuditorAware
bean for different types, you must provide the name of the bean to use as an argument to the auditorAwareRef
parameter of the
@EnableElasticsearchAuditing
annotation.
10. Entity Callbacks
The Spring Data infrastructure provides hooks for modifying an entity before and after certain methods are invoked.
Those so called EntityCallback
instances provide a convenient way to check and potentially modify an entity in a callback fashioned style.
An EntityCallback
looks pretty much like a specialized ApplicationListener
.
Some Spring Data modules publish store specific events (such as BeforeSaveEvent
) that allow modifying the given entity. In some cases, such as when working with immutable types, these events can cause trouble.
Also, event publishing relies on ApplicationEventMulticaster
. If configuring that with an asynchronous TaskExecutor
it can lead to unpredictable outcomes, as event processing can be forked onto a Thread.
Entity callbacks provide integration points with both synchronous and reactive APIs to guarantee in-order execution at well-defined checkpoints within the processing chain, returning a potentially modified entity or an reactive wrapper type.
Entity callbacks are typically separated by API type. This separation means that a synchronous API considers only synchronous entity callbacks and a reactive implementation considers only reactive entity callbacks.
The Entity Callback API has been introduced with Spring Data Commons 2.2. It is the recommended way of applying entity modifications.
Existing store specific |
10.1. Implementing Entity Callbacks
An EntityCallback
is directly associated with its domain type through its generic type argument.
Each Spring Data module typically ships with a set of predefined EntityCallback
interfaces covering the entity lifecycle.
EntityCallback
@FunctionalInterface
public interface BeforeSaveCallback<T> extends EntityCallback<T> {
/**
* Entity callback method invoked before a domain object is saved.
* Can return either the same or a modified instance.
*
* @return the domain object to be persisted.
*/
T onBeforeSave(T entity <2>, String collection <3>); (1)
}
1 | BeforeSaveCallback specific method to be called before an entity is saved. Returns a potentially modifed instance. |
2 | The entity right before persisting. |
3 | A number of store specific arguments like the collection the entity is persisted to. |
EntityCallback
@FunctionalInterface
public interface ReactiveBeforeSaveCallback<T> extends EntityCallback<T> {
/**
* Entity callback method invoked on subscription, before a domain object is saved.
* The returned Publisher can emit either the same or a modified instance.
*
* @return Publisher emitting the domain object to be persisted.
*/
Publisher<T> onBeforeSave(T entity <2>, String collection <3>); (1)
}
1 | BeforeSaveCallback specific method to be called on subscription, before an entity is saved. Emits a potentially modifed instance. |
2 | The entity right before persisting. |
3 | A number of store specific arguments like the collection the entity is persisted to. |
Optional entity callback parameters are defined by the implementing Spring Data module and inferred from call site of EntityCallback.callback() .
|
Implement the interface suiting your application needs like shown in the example below:
BeforeSaveCallback
class DefaultingEntityCallback implements BeforeSaveCallback<Person>, Ordered { (2)
@Override
public Object onBeforeSave(Person entity, String collection) { (1)
if(collection == "user") {
return // ...
}
return // ...
}
@Override
public int getOrder() {
return 100; (2)
}
}
1 | Callback implementation according to your requirements. |
2 | Potentially order the entity callback if multiple ones for the same domain type exist. Ordering follows lowest precedence. |
10.2. Registering Entity Callbacks
EntityCallback
beans are picked up by the store specific implementations in case they are registered in the ApplicationContext
.
Most template APIs already implement ApplicationContextAware
and therefore have access to the ApplicationContext
The following example explains a collection of valid entity callback registrations:
EntityCallback
Bean registration@Order(1) (1)
@Component
class First implements BeforeSaveCallback<Person> {
@Override
public Person onBeforeSave(Person person) {
return // ...
}
}
@Component
class DefaultingEntityCallback implements BeforeSaveCallback<Person>,
Ordered { (2)
@Override
public Object onBeforeSave(Person entity, String collection) {
// ...
}
@Override
public int getOrder() {
return 100; (2)
}
}
@Configuration
public class EntityCallbackConfiguration {
@Bean
BeforeSaveCallback<Person> unorderedLambdaReceiverCallback() { (3)
return (BeforeSaveCallback<Person>) it -> // ...
}
}
@Component
class UserCallbacks implements BeforeConvertCallback<User>,
BeforeSaveCallback<User> { (4)
@Override
public Person onBeforeConvert(User user) {
return // ...
}
@Override
public Person onBeforeSave(User user) {
return // ...
}
}
1 | BeforeSaveCallback receiving its order from the @Order annotation. |
2 | BeforeSaveCallback receiving its order via the Ordered interface implementation. |
3 | BeforeSaveCallback using a lambda expression. Unordered by default and invoked last. Note that callbacks implemented by a lambda expression do not expose typing information hence invoking these with a non-assignable entity affects the callback throughput. Use a class or enum to enable type filtering for the callback bean. |
4 | Combine multiple entity callback interfaces in a single implementation class. |
10.3. Elasticsearch EntityCallbacks
Spring Data Elasticsearch uses the EntityCallback
API internally for its auditing support and reacts on the following callbacks:
Callback | Method | Description | Order |
---|---|---|---|
Reactive/BeforeConvertCallback |
|
Invoked before a domain object is converted to |
|
Reactive/AfterConvertCallback |
|
Invoked after a domain object is converted from |
|
Reactive/AuditingEntityCallback |
|
Marks an auditable entity created or modified |
100 |
Reactive/AfterSaveCallback |
|
Invoked after a domain object is saved. |
|
11. Miscellaneous Elasticsearch Operation Support
This chapter covers additional support for Elasticsearch operations that cannot be directly accessed via the repository interface. It is recommended to add those operations as custom implementation as described in Custom Implementations for Spring Data Repositories .
11.1. Filter Builder
Filter Builder improves query speed.
private ElasticsearchOperations operations;
IndexCoordinates index = IndexCoordinates.of("sample-index");
SearchQuery searchQuery = new NativeSearchQueryBuilder()
.withQuery(matchAllQuery())
.withFilter(boolFilter().must(termFilter("id", documentId)))
.build();
Page<SampleEntity> sampleEntities = operations.searchForPage(searchQuery, SampleEntity.class, index);
11.2. Using Scroll For Big Result Set
Elasticsearch has a scroll API for getting big result set in chunks. This is internally used by Spring Data Elasticsearch to provide the implementations of the <T> SearchHitsIterator<T> SearchOperations.searchForStream(Query query, Class<T> clazz, IndexCoordinates index)
method.
IndexCoordinates index = IndexCoordinates.of("sample-index");
SearchQuery searchQuery = new NativeSearchQueryBuilder()
.withQuery(matchAllQuery())
.withFields("message")
.withPageable(PageRequest.of(0, 10))
.build();
SearchHitsIterator<SampleEntity> stream = elasticsearchTemplate.searchForStream(searchQuery, SampleEntity.class, index);
List<SampleEntity> sampleEntities = new ArrayList<>();
while (stream.hasNext()) {
sampleEntities.add(stream.next());
}
stream.close();
There are no methods in the SearchOperations
API to access the scroll id, if it should be necessary to access this, the following methods of the ElasticsearchRestTemplate
can be used:
@Autowired ElasticsearchRestTemplate template;
IndexCoordinates index = IndexCoordinates.of("sample-index");
SearchQuery searchQuery = new NativeSearchQueryBuilder()
.withQuery(matchAllQuery())
.withFields("message")
.withPageable(PageRequest.of(0, 10))
.build();
SearchScrollHits<SampleEntity> scroll = template.searchScrollStart(1000, searchQuery, SampleEntity.class, index);
String scrollId = scroll.getScrollId();
List<SampleEntity> sampleEntities = new ArrayList<>();
while (scroll.hasSearchHits()) {
sampleEntities.addAll(scroll.getSearchHits());
scrollId = scroll.getScrollId();
scroll = template.searchScrollContinue(scrollId, 1000, SampleEntity.class);
}
template.searchScrollClear(scrollId);
To use the Scroll API with repository methods, the return type must defined as Stream
in the Elasticsearch Repository. The implementation of the method will then use the scroll methods from the ElasticsearchTemplate.
interface SampleEntityRepository extends Repository<SampleEntity, String> {
Stream<SampleEntity> findBy();
}
11.3. Sort options
In addition to the default sort options described Paging and Sorting Spring Data Elasticsearch has a GeoDistanceOrder
class which can be used to have the result of a search operation ordered by geographical distance.
If the class to be retrieved has a GeoPoint
property named location, the following Sort
would sort the results by distance to the given point:
Sort.by(new GeoDistanceOrder("location", new GeoPoint(48.137154, 11.5761247)))
11.4. Join-Type implementation
Spring Data Elasticsearch supports the Join data type for creating the corresponding index mappings and for storing the relevant information.
11.4.1. Setting up the data
For an entity to be used in a parent child join relationship, it must have a property of type JoinField
which must be annotated.
Let’s assume a Statement
entity where a statement may be a question, an answer, a comment or a vote (a Builder is also shown in this example, it’s not necessary, but later used in the sample code):
@Document(indexName = "statements")
public class Statement {
@Id
private String id;
@Field(type = FieldType.Text)
private String text;
@JoinTypeRelations(
relations =
{
@JoinTypeRelation(parent = "question", children = {"answer", "comment"}), (1)
@JoinTypeRelation(parent = "answer", children = "vote") (2)
}
)
private JoinField<String> relation; (3)
private Statement() {
}
public static StatementBuilder builder() {
return new StatementBuilder();
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getText() {
return text;
}
public void setText(String text) {
this.text = text;
}
public JoinField<String> getRelation() {
return relation;
}
public void setRelation(JoinField<String> relation) {
this.relation = relation;
}
public static final class StatementBuilder {
private String id;
private String text;
private JoinField<String> relation;
private StatementBuilder() {
}
public StatementBuilder withId(String id) {
this.id = id;
return this;
}
public StatementBuilder withText(String text) {
this.text = text;
return this;
}
public StatementBuilder withRelation(JoinField<String> relation) {
this.relation = relation;
return this;
}
public Statement build() {
Statement statement = new Statement();
statement.setId(id);
statement.setText(text);
statement.setRelation(relation);
return statement;
}
}
}
1 | a question can have answers and comments |
2 | an answer can have votes |
3 | the JoinField property is used to combine the name (question, answer, comment or vote) of the relation with the parent id. The generic type must be the same as the @Id annotated property. |
Spring Data Elasticsearch will build the following mapping for this class:
{
"statements": {
"mappings": {
"properties": {
"_class": {
"type": "text",
"fields": {
"keyword": {
"type": "keyword",
"ignore_above": 256
}
}
},
"relation": {
"type": "join",
"eager_global_ordinals": true,
"relations": {
"question": [
"answer",
"comment"
],
"answer": "vote"
}
},
"text": {
"type": "text"
}
}
}
}
}
11.4.2. Storing data
Given a repository for this class the following code inserts a question, two answers, a comment and a vote:
void init() {
repository.deleteAll();
Statement savedWeather = repository.save(
Statement.builder()
.withText("How is the weather?")
.withRelation(new JoinField<>("question")) (1)
.build());
Statement sunnyAnswer = repository.save(
Statement.builder()
.withText("sunny")
.withRelation(new JoinField<>("answer", savedWeather.getId())) (2)
.build());
repository.save(
Statement.builder()
.withText("rainy")
.withRelation(new JoinField<>("answer", savedWeather.getId())) (3)
.build());
repository.save(
Statement.builder()
.withText("I don't like the rain")
.withRelation(new JoinField<>("comment", savedWeather.getId())) (4)
.build());
repository.save(
Statement.builder()
.withText("+1 for the sun")
.withRelation(new JoinField<>("vote", sunnyAnswer.getId())) (5)
.build());
}
1 | create a question statement |
2 | the first answer to the question |
3 | the second answer |
4 | a comment to the question |
5 | a vote for the first answer |
11.4.3. Retrieving data
Currently native search queries must be used to query the data, so there is no support from standard repository methods. Custom Implementations for Spring Data Repositories can be used instead.
The following code shows as an example how to retrieve all entries that have a vote (which must be answers, because only answers can have a vote) using an ElasticsearchOperations
instance:
SearchHits<Statement> hasVotes() {
NativeSearchQuery query = new NativeSearchQueryBuilder()
.withQuery(hasChildQuery("vote", matchAllQuery(), ScoreMode.None))
.build();
return operations.search(query, Statement.class);
}
Appendix
Appendix A: Namespace reference
The <repositories />
Element
The <repositories />
element triggers the setup of the Spring Data repository infrastructure. The most important attribute is base-package
, which defines the package to scan for Spring Data repository interfaces. See “XML Configuration”. The following table describes the attributes of the <repositories />
element:
Name | Description |
---|---|
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Defines the package to be scanned for repository interfaces that extend |
|
Defines the postfix to autodetect custom repository implementations. Classes whose names end with the configured postfix are considered as candidates. Defaults to |
|
Determines the strategy to be used to create finder queries. See “Query Lookup Strategies” for details. Defaults to |
|
Defines the location to search for a Properties file containing externally defined queries. |
|
Whether nested repository interface definitions should be considered. Defaults to |
Appendix B: Populators namespace reference
The <populator /> element
The <populator />
element allows to populate the a data store via the Spring Data repository infrastructure.[3]
Name | Description |
---|---|
|
Where to find the files to read the objects from the repository shall be populated with. |
Appendix C: Repository query keywords
Supported query keywords
The following table lists the keywords generally supported by the Spring Data repository query derivation mechanism. However, consult the store-specific documentation for the exact list of supported keywords, because some keywords listed here might not be supported in a particular store.
Logical keyword | Keyword expressions |
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Appendix D: Repository query return types
Supported Query Return Types
The following table lists the return types generally supported by Spring Data repositories. However, consult the store-specific documentation for the exact list of supported return types, because some types listed here might not be supported in a particular store.
Geospatial types (such as GeoResult , GeoResults , and GeoPage ) are available only for data stores that support geospatial queries.
|
Return type | Description |
---|---|
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Denotes no return value. |
Primitives |
Java primitives. |
Wrapper types |
Java wrapper types. |
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A unique entity. Expects the query method to return one result at most. If no result is found, |
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An |
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A |
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A |
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A Java 8 or Guava |
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Either a Scala or Vavr |
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A Java 8 |
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A convenience extension of |
Types that implement |
Types that expose a constructor or |
Vavr |
Vavr collection types. See Support for Vavr Collections for details. |
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A |
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A Java 8 |
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A |
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A sized chunk of data with an indication of whether there is more data available. Requires a |
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A |
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A result entry with additional information, such as the distance to a reference location. |
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A list of |
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A |
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A Project Reactor |
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A Project Reactor |
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A RxJava |
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A RxJava |
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A RxJava |
Appendix E: Migration Guides
Upgrading from 3.2.x to 4.0.x
This section describes breaking changes from version 3.2.x to 4.0.x and how removed features can be replaced by new introduced features.
Removal of the used Jackson Mapper
One of the changes in version 4.0.x is that Spring Data Elasticsearch does not use the Jackson Mapper anymore to map an entity to the JSON representation needed for Elasticsearch (see Elasticsearch Object Mapping). In version 3.2.x the Jackson Mapper was the default that was used. It was possible to switch to the meta-model based converter (named ElasticsearchEntityMapper
) by explicitly configuring it (Meta Model Object Mapping).
In version 4.0.x the meta-model based converter is the only one that is available and does not need to be configured explicitly. If you had a custom configuration to enable the meta-model converter by providing a bean like this:
@Bean
@Override
public EntityMapper entityMapper() {
ElasticsearchEntityMapper entityMapper = new ElasticsearchEntityMapper(
elasticsearchMappingContext(), new DefaultConversionService()
);
entityMapper.setConversions(elasticsearchCustomConversions());
return entityMapper;
}
You now have to remove this bean, the ElasticsearchEntityMapper
interface has been removed.
Some users had custom Jackson annotations on the entity class, for example in order to define a custom name for the mapped document in Elasticsearch or to configure date conversions. These are not taken into account anymore. The needed functionality is now provided with Spring Data Elasticsearch’s @Field
annotation. Please see Mapping Annotation Overview for detailed information.
Removal of implicit index name from query objects
In 3.2.x the different query classes like IndexQuery
or SearchQuery
had properties that were taking the index name or index names that they were operating upon. If these were not set, the passed in entity was inspected to retrieve the index name that was set in the @Document
annotation.
In 4.0.x the index name(s) must now be provided in an additional parameter of type IndexCoordinates
. By separating this, it now is possible to use one query object against different indices.
So for example the following code:
IndexQuery indexQuery = new IndexQueryBuilder()
.withId(person.getId().toString())
.withObject(person)
.build();
String documentId = elasticsearchOperations.index(indexQuery);
must be changed to:
IndexCoordinates indexCoordinates = elasticsearchOperations.getIndexCoordinatesFor(person.getClass());
IndexQuery indexQuery = new IndexQueryBuilder()
.withId(person.getId().toString())
.withObject(person)
.build();
String documentId = elasticsearchOperations.index(indexQuery, indexCoordinates);
To make it easier to work with entities and use the index name that is contained in the entitie’s @Document
annotation, new methods have been added like DocumentOperations.save(T entity)
;
The new Operations interfaces
In version 3.2 there was the ElasticsearchOperations
interface that defined all the methods for the ElasticsearchTemplate
class. In version 4 the functions have been split into different interfaces, aligning these interfaces with the Elasticsearch API:
-
DocumentOperations
are the functions related documents like saving, or deleting -
SearchOperations
contains the functions to search in Elasticsearch -
IndexOperations
define the functions to operate on indexes, like index creation or mappings creation.
ElasticsearchOperations
now extends DocumentOperations
and SearchOperations
and has methods get access to an IndexOperations
instance.
All the functions from the ElasticsearchOperations interface in version 3.2 that are now moved to the IndexOperations interface are still available, they are marked as deprecated and have default implementations that delegate to the new implementation:
|
/**
* Create an index for given indexName.
*
* @param indexName the name of the index
* @return {@literal true} if the index was created
* @deprecated since 4.0, use {@link IndexOperations#create()}
*/
@Deprecated
default boolean createIndex(String indexName) {
return indexOps(IndexCoordinates.of(indexName)).create();
}
Deprecations
Methods and classes
Many functions and classes have been deprecated. These functions still work, but the Javadocs show with what they should be replaced.
/*
* Retrieves an object from an index.
*
* @param query the query defining the id of the object to get
* @param clazz the type of the object to be returned
* @return the found object
* @deprecated since 4.0, use {@link #get(String, Class, IndexCoordinates)}
*/
@Deprecated
@Nullable
<T> T queryForObject(GetQuery query, Class<T> clazz);
Elasticsearch deprecations
Since version 7 the Elasticsearch TransportClient
is deprecated, it will be removed with Elasticsearch version 8. Spring Data Elasticsearch deprecates the ElasticsearchTemplate
class which uses the TransportClient
in version 4.0.
Mapping types were removed from Elasticsearch 7, they still exist as deprecated values in the Spring Data @Document
annotation and the IndexCoordinates
class but they are not used anymore internally.
Removals
-
As already described, the
ElasticsearchEntityMapper
interface has been removed. -
The
SearchQuery
interface has been merged into it’s base interfaceQuery
, so it’s occurrences can just be replaced withQuery
. -
The method
org.springframework.data.elasticsearch.core.ElasticsearchOperations.query(SearchQuery query, ResultsExtractor<T> resultsExtractor);
and theorg.springframework.data.elasticsearch.core.ResultsExtractor
interface have been removed. These could be used to parse the result from Elasticsearch for cases in which the response mapping done with the Jackson based mapper was not enough. Since version 4.0, there are the new Search Result Types to return the information from an Elasticsearch response, so there is no need to expose this low level functionality. -
The low level methods
startScroll
,continueScroll
andclearScroll
have been removed from theElasticsearchOperations
interface. For low level scroll API access, there now aresearchScrollStart
,searchScrollContinue
andsearchScrollClear
methods on theElasticsearchRestTemplate
class.
Upgrading from 4.0.x to 4.1.x
This section describes breaking changes from version 4.0.x to 4.1.x and how removed features can be replaced by new introduced features.
Deprecations
It is possible to define a property of en entity as the id property by naming it either id
or document
.
This behaviour is now deprecated and will produce a warning.
PLease us the @Id
annotation to mark a property as being the id property.
In the ReactiveElasticsearchClient.Indices
interface the updateMapping
methods are deprecated in favour of the putMapping
methods.
They do the same, but putMapping
is consistent with the naming in the Elasticsearch API:
In the IndexOperations
interface the methods addAlias(AliasQuery)
, removeAlias(AliasQuery)
and queryForAlias()
have been deprecated.
The new methods alias(AliasAction)
, getAliases(String…)
and getAliasesForIndex(String…)
offer more functionality and a cleaner API.
Usage of a parent-id has been removed from Elasticsearch since version 6. We now deprecate the corresponding fields and methods.
Removals
The type mappings parameters of the @Document
annotation and the IndexCoordinates
object were removed.
They had been deprecated in Spring Data Elasticsearch 4.0 and their values weren’t used anymore.
Breaking Changes
Return types of ReactiveElasticsearchClient.Indices methods
The methods in the ReactiveElasticsearchClient.Indices
were not used up to now.
With the introduction of the ReactiveIndexOperations
it became necessary to change some of the return types:
-
the
createIndex
variants now return aMono<Boolean>
instead of aMono<Void>
to signal successful index creation. -
the
updateMapping
variants now return aMono<Boolean>
instead of aMono<Void>
to signal successful mappings storage.
Return types of DocumentOperartions.bulkIndex methods
These methods were returing a List<String>
containing the ids of the new indexed records.
Now they return a List<IndexedObjectInformation>
; these objects contain the id and information about optimistic locking (seq_no and primary_term)
:leveloffset: -1
:leveloffset: -1