The goal of Spring Data repository abstraction is to significantly reduce the amount of boilerplate code required to implement data access layers for various persistence stores.
Important | |
---|---|
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. Adapt the XML namespace declaration and the types to be extended to the equivalents of the particular module that you are using. Appendix A, Namespace reference covers XML configuration which is supported across all Spring Data modules supporting the repository API, Appendix B, Repository query keywords covers the query method method keywords supported by the repository abstraction in general. For detailed information on the specific features of your module, consult the chapter on that module of this document. |
The central interface in Spring Data repository abstraction is
Repository
(probably not that much of a
surprise). It takes the 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
provides sophisticated CRUD
functionality for the entity class that is being managed.
Example 1.1. CrudRepository
interface
public interface CrudRepository<T, ID extends Serializable> extends Repository<T, ID> { <S extends T> S save(S entity); T findOne(ID primaryKey); Iterable<T> findAll(); Long count(); void delete(T entity); boolean exists(ID primaryKey); // … more functionality omitted. }
Saves the given entity. | |
Returns the entity identified by the given id. | |
Returns all entities. | |
Returns the number of entities. | |
Deletes the given entity. | |
Indicates whether an entity with the given id exists. |
Usually we will have persistence technology specific sub-interfaces
to include additional technology specific methods. We will now ship
implementations for a variety of Spring Data modules that implement
CrudRepository
.
On top of the CrudRepository
there is
a PagingAndSortingRepository
abstraction
that adds additional methods to ease paginated access to entities:
Example 1.2. PagingAndSortingRepository
public interface PagingAndSortingRepository<T, ID extends Serializable> extends CrudRepository<T, ID> { Iterable<T> findAll(Sort sort); Page<T> findAll(Pageable pageable); }
Accessing the second page of User
by a page
size of 20 you could simply do something like this:
PagingAndSortingRepository<User, Long> repository = // … get access to a bean Page<User> users = repository.findAll(new PageRequest(1, 20));
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 that it will handle.
public interface PersonRepository extends Repository<User, Long> { … }
Declare query methods on the interface.
List<Person> findByLastname(String lastname);
Set up Spring to create proxy instances for those interfaces.
<?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 http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa.xsd"> <repositories base-package="com.acme.repositories" /> </beans>
Note | |
---|---|
The JPA namespace is used in this example. If you are using
the repository abstraction for any other store, you need to change
this to the appropriate namespace declaration of your store module
which should be exchanging |
Get the repository instance injected and use it.
public class SomeClient { @Autowired private PersonRepository repository; public void doSomething() { List<Person> persons = repository.findByLastname("Matthews"); } }
The sections that follow explain each step.
As a first step you 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
.
Typically, your repository interface will extend
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, simply copy the ones you
want to expose from CrudRepository
into
your domain repository.
Example 1.3. Selectively exposing CRUD methods
interface MyBaseRepository<T, ID extends Serializable> extends Repository<T, ID> { T findOne(ID id); T save(T entity); } interface UserRepository extends MyBaseRepository<User, Long> { User findByEmailAddress(EmailAddress emailAddress); }
In this first step you defined a common base interface for all
your domain repositories and exposed
findOne(…)
as well as
save(…)
.These methods will be routed into the
base repository implementation of the store of your choice provided by
Spring Data because they are matching the method signatures in
CrudRepository
. So the
UserRepository
will now be able to save
users, and find single ones by id, as well as triggering a query to
find User
s by their email
address.
The repository proxy has two ways to derive a store-specific query from the method name. It can derive the query from the method name directly, or by using an additionally created query. Available options depend on the actual store. However, there's got to be an strategy that decides what actual query is created. Let's have a look at the available options.
The following strategies are available for the repository
infrastructure to resolve the query. You can configure the strategy at
the namespace through the query-lookup-strategy
attribute. 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. Read more about query construction in the section called “Query creation”.
USE_DECLARED_QUERY
tries to find a declared query
and will throw an exception in case it can't find one. The query can
be defined by an annotation somewhere or declared by other means.
Consult 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
combines CREATE
and USE_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 will
be 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.
The query builder mechanism built into Spring Data repository
infrastructure is useful for building constraining queries over
entities of the repository. The mechanism strips the prefixes
find…By
, read…By
, and get…By
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 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
.
Example 1.4. Query creation from method names
public interface PersonRepository extends Repository<User, 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
and OR
.
You also get support for operators such as
Between
, LessThan
,
GreaterThan
, Like
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 support ignoring case (usually
String
s, 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
or Desc
). To create a query
method that supports dynamic sorting, see the section called “Special parameter handling”.
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. Assume Person
s
have Address
es with
ZipCode
s. In that case a method name of
List<Person> findByAddressZipCode(ZipCode zipCode);
creates the property traversal x.address.zipCode
.
The resolution algorithm starts with 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
continue building the tree down from there, splitting the tail up in
the way just described. If the first split does not match, the
algorithm move 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 and essentially choose the wrong
property and finally 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 end up like
so:
List<Person> findByAddress_ZipCode(ZipCode zipCode);
To handle parameters to your query you simply define method
parameters as already seen in the examples above. Besides that the
infrastructure will recognize certain specific types like
Pageable
and
Sort
to apply pagination and sorting to your
queries dynamically.
Example 1.5. Using Pageable and Sort in query methods
Page<User> findByLastname(String lastname, Pageable pageable); List<User> findByLastname(String lastname, Sort sort); List<User> findByLastname(String lastname, Pageable pageable);
The first method allows you to pass an
org.springframework.data.domain.Pageable
instance to the
query method to dynamically add paging to your statically defined
query. Sorting options are handled through the
Pageable
instance too. If you only need
sorting, simply add an
org.springframework.data.domain.Sort
parameter to your
method. As you also can see, simply returning a
List
is possible as well. In this case
the additional metadata required to build the actual
Page
instance will not be created
(which in turn means that the additional count query that would have
been necessary not being issued) but rather simply restricts the query
to look up only the given range of entities.
Note | |
---|---|
To find out how many pages you get for a query entirely you have to trigger an additional count query. By default this query will be derived from the query you actually trigger. |
In this section you create instances and bean definitions for the repository interfaces defined. The easiest way to do so is by using the Spring namespace that is shipped with each Spring Data module that supports the repository mechanism.
Each Spring Data module includes a repositories element that allows you to simply define a base package that Spring scans for you.
<?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 http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/data/jpa http://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 subpackages for
interfaces extending Repository
or one
of its subinterfaces. 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
. The
base-package
attribute allows wildcards, so that you can
have a pattern of scanned packages.
By default the infrastructure picks up every interface
extending the persistence technology-specific
Repository
subinterface located under
the configured base package and creates a bean instance for it.
However, you might want more fine-grained control over which
interfaces bean instances get created for. To do this you use
<include-filter />
and <exclude-filter
/>
elements inside <repositories />
.
The semantics are exactly equivalent to the elements in Spring's
context namespace. For details, see Spring reference documentation on these
elements.
For example, to exclude certain interfaces from instantiation as repository, you could use the following configuration:
Example 1.6. Using exclude-filter element
<repositories base-package="com.acme.repositories"> <context:exclude-filter type="regex" expression=".*SomeRepository" /> </repositories>
This example excludes all interfaces ending in
SomeRepository
from being
instantiated.
The repository infrastructure can also be triggered using a
store-specific
@Enable${store}Repositories
annotation
on a JavaConfig class. For an introduction into Java-based
configuration of the Spring container, see the reference
documentation.[1]
A sample configuration to enable Spring Data repositories looks something like this.
Example 1.7. Sample annotation based repository configuration
@Configuration @EnableJpaRepositories("com.acme.repositories") class ApplicationConfiguration { @Bean public EntityManagerFactory entityManagerFactory() { // … } }
Note | |
---|---|
The sample 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
|
You can also use the repository infrastructure outside of a
Spring container. 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
a persistence technology-specific
RepositoryFactory
that you can use as
follows.
Example 1.8. Standalone usage of repository factory
RepositoryFactorySupport factory = … // Instantiate factory here UserRepository repository = factory.getRepository(UserRepository.class);
Often it is necessary to provide a custom implementation for a few repository methods. Spring Data repositories easily allow you to provide custom repository code and integrate it with generic CRUD abstraction and query method functionality.
To enrich a repository with custom functionality you first define an interface and an implementation for the custom functionality. Use the repository interface you provided to extend the custom interface.
Example 1.9. Interface for custom repository functionality
interface UserRepositoryCustom { public void someCustomMethod(User user); }
Example 1.10. Implementation of custom repository functionality
class UserRepositoryImpl implements UserRepositoryCustom { public void someCustomMethod(User user) { // Your custom implementation } }
Note | |
---|---|
The implementation itself does not depend on Spring Data and can be a regular Spring bean. So you can use standard dependency injection behavior to inject references to other beans, take part in aspects, and so on. |
Example 1.11. Changes to the your basic repository interface
public interface UserRepository extends CrudRepository<User, Long>, UserRepositoryCustom { // Declare query methods here }
Let your standard repository interface extend the custom one. Doing so makes CRUD and custom functionality available to clients.
If you use namespace configuration, the repository
infrastructure tries to autodetect custom implementations by scanning
for classes below the package we found a repository in. These classes
need to follow the naming convention of appending the namespace
element's attribute repository-impl-postfix
to the found
repository interface name. This postfix defaults to
Impl
.
Example 1.12. Configuration example
<repositories base-package="com.acme.repository" /> <repositories base-package="com.acme.repository" repository-impl-postfix="FooBar" />
The first configuration example will try to look up a class
com.acme.repository.UserRepositoryImpl
to act
as custom repository implementation, where the second example will try
to lookup
com.acme.repository.UserRepositoryFooBar
.
The preceding approach works well if your custom implementation uses annotation-based configuration and autowiring only, as it will be treated as any other Spring bean. If your custom implementation bean needs special wiring, you simply declare the bean and name it after the conventions just described. The infrastructure will then refer to the manually defined bean definition by name instead of creating one itself.
Example 1.13. Manual wiring of custom implementations (I)
<repositories base-package="com.acme.repository" /> <beans:bean id="userRepositoryImpl" class="…"> <!-- further configuration --> </beans:bean>
The preceding approach is not feasible when you want to add a single method to all your repository interfaces.
To add custom behavior to all repositories, you first add an intermediate interface to declare the shared behavior.
Example 1.14. An interface declaring custom shared behavior
public interface MyRepository<T, ID extends Serializable> extends JpaRepository<T, ID> { void sharedCustomMethod(ID id); }
Now your individual repository interfaces will extend this
intermediate interface instead of the
Repository
interface to include the
functionality declared.
Next, create an implementation of the intermediate interface that extends the persistence technology-specific repository base class. This class will then act as a custom base class for the repository proxies.
Example 1.15. Custom repository base class
public class MyRepositoryImpl<T, ID extends Serializable> extends SimpleJpaRepository<T, ID> implements MyRepository<T, ID> { private EntityManager entityManager; // There are two constructors to choose from, either can be used. public MyRepositoryImpl(Class<T> domainClass, EntityManager entityManager) { super(domainClass, entityManager); // This is the recommended method for accessing inherited class dependencies. this.entityManager = entityManager; } public void sharedCustomMethod(ID id) { // implementation goes here } }
The default behavior of the Spring <repositories
/>
namespace is to provide an implementation for all
interfaces that fall under the base-package
. This means
that if left in its current state, an implementation instance of
MyRepository
will be created by
Spring. This is of course not desired as it is just supposed to act
as an intermediary between Repository
and the actual repository interfaces you want to define for each
entity. To exclude an interface that extends
Repository
from being instantiated as
a repository instance, you can either annotate it with
@NoRepositoryBean
or move it outside
of the configured base-package
.
Then create a custom repository factory to replace the default
RepositoryFactoryBean
that will in turn
produce a custom RepositoryFactory
. The new
repository factory will then provide your
MyRepositoryImpl
as the implementation of any
interfaces that extend the Repository
interface, replacing the SimpleJpaRepository
implementation you just extended.
Example 1.16. Custom repository factory bean
public class MyRepositoryFactoryBean<R extends JpaRepository<T, I>, T, I extends Serializable> extends JpaRepositoryFactoryBean<R, T, I> { protected RepositoryFactorySupport createRepositoryFactory(EntityManager entityManager) { return new MyRepositoryFactory(entityManager); } private static class MyRepositoryFactory<T, I extends Serializable> extends JpaRepositoryFactory { private EntityManager entityManager; public MyRepositoryFactory(EntityManager entityManager) { super(entityManager); this.entityManager = entityManager; } protected Object getTargetRepository(RepositoryMetadata metadata) { return new MyRepositoryImpl<T, I>((Class<T>) metadata.getDomainClass(), entityManager); } protected Class<?> getRepositoryBaseClass(RepositoryMetadata metadata) { // The RepositoryMetadata can be safely ignored, it is used by the JpaRepositoryFactory //to check for QueryDslJpaRepository's which is out of scope. return MyRepository.class; } } }
Finally, either declare beans of the custom factory directly
or use the factory-class
attribute of the Spring
namespace to tell the repository infrastructure to use your custom
factory implementation.
Example 1.17. Using the custom factory with the namespace
<repositories base-package="com.acme.repository" factory-class="com.acme.MyRepositoryFactoryBean" />
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.
Given you are developing a Spring MVC web application you typically have to resolve domain class ids from URLs. By default your task is to transform that request parameter or URL part into the domain class to hand it to layers below then or execute business logic on the entities directly. This would look something like this:
@Controller @RequestMapping("/users") public class UserController { private final UserRepository userRepository; @Autowired public UserController(UserRepository userRepository) { Assert.notNull(repository, "Repository must not be null!"); userRepository = userRepository; } @RequestMapping("/{id}") public String showUserForm(@PathVariable("id") Long id, Model model) { // Do null check for id User user = userRepository.findOne(id); // Do null check for user model.addAttribute("user", user); return "user"; } }
First you declare a repository dependency for each controller to
look up the entity managed by the controller or repository respectively.
Looking up the entity is boilerplate as well, as it's always a
findOne(…)
call. Fortunately Spring provides
means to register custom components that allow conversion between a
String
value to an arbitrary type.
For Spring versions before 3.0 simple Java
PropertyEditor
s had to be used. To
integrate with that, Spring Data offers a
DomainClassPropertyEditorRegistrar
, which looks
up all Spring Data repositories registered in the
ApplicationContext
and registers a
custom PropertyEditor
for the managed
domain class.
<bean class="….web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"> <property name="webBindingInitializer"> <bean class="….web.bind.support.ConfigurableWebBindingInitializer"> <property name="propertyEditorRegistrars"> <bean class="org.springframework.data.repository.support.DomainClassPropertyEditorRegistrar" /> </property> </bean> </property> </bean>
If you have configured Spring MVC as in the preceding example, you can configure your controller as follows, which reduces a lot of the clutter and boilerplate.
@Controller @RequestMapping("/users") public class UserController { @RequestMapping("/{id}") public String showUserForm(@PathVariable("id") User user, Model model) { model.addAttribute("user", user); return "userForm"; } }
In Spring 3.0 and later the
PropertyEditor
support is superseded by
a new conversion infrastructure that eliminates the drawbacks of
PropertyEditor
s and uses a stateless X
to Y conversion approach. Spring Data now ships with a
DomainClassConverter
that mimics the behavior
of DomainClassPropertyEditorRegistrar
. To
configure, simply declare a bean instance and pipe the
ConversionService
being used into its
constructor:
<mvc:annotation-driven conversion-service="conversionService" /> <bean class="org.springframework.data.repository.support.DomainClassConverter"> <constructor-arg ref="conversionService" /> </bean>
If you are using JavaConfig, you can simply extend Spring MVC's
WebMvcConfigurationSupport
and hand the
FormatingConversionService
that the
configuration superclass provides into the
DomainClassConverter
instance you
create.
class WebConfiguration extends WebMvcConfigurationSupport { // Other configuration omitted @Bean public DomainClassConverter<?> domainClassConverter() { return new DomainClassConverter<FormattingConversionService>(mvcConversionService()); } }
When working with pagination in the web layer you usually have to
write a lot of boilerplate code yourself to extract the necessary
metadata from the request. The less desirable approach shown in the
example below requires the method to contain an
HttpServletRequest
parameter that has to
be parsed manually. This example also omits appropriate failure
handling, which would make the code even more verbose.
@Controller @RequestMapping("/users") public class UserController { // DI code omitted @RequestMapping public String showUsers(Model model, HttpServletRequest request) { int page = Integer.parseInt(request.getParameter("page")); int pageSize = Integer.parseInt(request.getParameter("pageSize")); Pageable pageable = new PageRequest(page, pageSize); model.addAttribute("users", userService.getUsers(pageable)); return "users"; } }
The bottom line is that the controller should not have to handle
the functionality of extracting pagination information from the request.
So Spring includes a PageableArgumentResolver
that will do the work for you.
<bean class="….web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"> <property name="customArgumentResolvers"> <list> <bean class="org.springframework.data.web.PageableArgumentResolver" /> </list> </property> </bean>
This configuration allows you to simplify controllers down to something like this:
@Controller @RequestMapping("/users") public class UserController { @RequestMapping public String showUsers(Model model, Pageable pageable) { model.addAttribute("users", userRepository.findAll(pageable)); return "users"; } }
The PageableArgumentResolver
automatically
resolves request parameters to build a
PageRequest
instance. By default it expects the
following structure for the request parameters.
Table 1.1. Request parameters evaluated by
PageableArgumentResolver
page | Page you want to retrieve. |
page.size | Size of the page you want to retrieve. |
page.sort | Property that should be sorted by. |
page.sort.dir | Direction that should be used for sorting. |
In case you need multiple Pageable
s
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}_
. So for a method signature like
this:
public String showUsers(Model model, @Qualifier("foo") Pageable first, @Qualifier("bar") Pageable second) { … }
you have to populate foo_page
and
bar_page
and the related subproperties.
The PageableArgumentResolver
will use a
PageRequest
with the first page and a page size
of 10 by default. It will use that value if it cannot resolve a
PageRequest
from the request (because of
missing parameters, for example). You can configure a global default
on the bean declaration directly. If you might need controller method
specific defaults for the Pageable
,
annotate the method parameter with
@PageableDefaults
and specify page
(through pageNumber
), page size (through
value
), sort
(list of properties to sort
by), and sortDir
(the direction to sort by) as annotation
attributes:
public String showUsers(Model model, @PageableDefaults(pageNumber = 0, value = 30) Pageable pageable) { … }
If you work with the Spring JDBC module, you probably are familiar
with the support to populate a DataSource
using 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 data.json
with the
following content:
Example 1.18. Data defined in JSON
[ { "_class" : "com.acme.Person", "firstname" : "Dave", "lastname" : "Matthews" }, { "_class" : "com.acme.Person", "firstname" : "Carter", "lastname" : "Beauford" } ]
You can easily 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
, do the
following:
Example 1.19. Declaring a Jackson repository populator
<?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 http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/data/repository http://www.springframework.org/schema/data/repository/spring-repository.xsd"> <repository:jackson-populator location="classpath:data.json" /> </beans>
This declaration causes the data.json
file
being read, deserialized by a Jackson
ObjectMapper
. The type to which the JSON object will be unmarshalled to will
be determined by inspecting the _class
attribute of the
JSON document. The infrastructure will eventually select the appropriate
repository to handle the object just deserialized.
To rather use XML to define the data the repositories shall be
populated with, you can use the unmarshaller-populator
element. You configure it to use one of the XML marshaller options
Spring OXM provides you with. See the Spring reference
documentation for details.
Example 1.20. Declaring an unmarshalling repository populator (using 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 http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/data/repository http://www.springframework.org/schema/data/repository/spring-repository.xsd http://www.springframework.org/schema/oxm http://www.springframework.org/schema/oxm/spring-oxm.xsd"> <repository:unmarshaller-populator location="classpath:data.json" unmarshaller-ref="unmarshaller" /> <oxm:jaxb2-marshaller contextPath="com.acme" /> </beans>
[1] JavaConfig in the Spring reference documentation - http://static.springsource.org/spring/docs/3.1.x/spring-framework-reference/html/beans.html#beans-java