Abstract
This chapter includes details of the JPA repository implementation.
The JPA module of Spring Data contains a custom namespace that
allows defining repository beans. It also contains certain features and
element attributes that are special to JPA. Generally the JPA
repositories can be set up using the repositories
element:
Example 2.1. Setting up JPA repositories using the namespace
<?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 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"> <jpa:repositories base-package="com.acme.repositories" /> </beans>
Using this element looks up Spring Data repositories as described
in Section 1.2.3, “Creating repository instances”. Beyond that it
activates persistence exception translation for all beans annotated with
@Repository
to let exceptions being
thrown by the JPA persistence providers be converted into Spring's
DataAccessException
hierarchy.
Beyond the default attributes of the repositories
element the JPA namespace offers additional attributes to gain more
detailed control over the setup of the repositories:
Table 2.1. Custom JPA-specific attributes of the repositories element
entity-manager-factory-ref | Explicitly wire the
EntityManagerFactory to be used
with the repositories being detected by the
repositories element. Usually used if multiple
EntityManagerFactory beans are
used within the application. If not configured we will
automatically lookup the
EntityManagerFactory bean with
the name entityManagerFactory in the
ApplicationContext . |
transaction-manager-ref | Explicitly wire the
PlatformTransactionManager to
be used with the repositories being detected by the
repositories element. Usually only necessary if
multiple transaction managers and/or
EntityManagerFactory beans have
been configured. Default to a single defined
PlatformTransactionManager
inside the current
ApplicationContext . |
Note that we require a
PlatformTransactionManager
bean named
transactionManager
to be present if no explicit
transaction-manager-ref
is defined.
The Spring Data JPA repositories support cannot only be activated through an XML namespace but also using an annotation through JavaConfig.
Example 2.2. Spring Data JPA repositories using JavaConfig
@Configuration @EnableJpaRepositories @EnableTransactionManagement class ApplicationConfig { @Bean public DataSource dataSource() { EmbeddedDatabaseBuilder builder = new EmbeddedDatabaseBuilder(); return builder.setType(EmbeddedDatabaseType.HSQL).build(); } @Bean public EntityManagerFactory entityManagerFactory() { HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter(); vendorAdapter.setGenerateDdl(true); LocalContainerEntityManagerFactoryBean factory = new LocalContainerEntityManagerFactoryBean(); factory.setJpaVendorAdapter(vendorAdapter); factory.setPackagesToScan("com.acme.domain"); factory.setDataSource(dataSource()); factory.afterPropertiesSet(); return factory.getObject(); } @Bean public PlatformTransactionManager transactionManager() { JpaTransactionManager txManager = new JpaTransactionManager(); txManager.setEntityManagerFactory(entityManagerFactory()); return txManager; } }
The just shown configuration class sets up an embedded HSQL
database using the EmbeddedDatabaseBuilder
API of
spring-jdbc. We then set up a
EntityManagerFactory
and use Hibernate as
sample persistence provider. The last infrastructure component declared
here is the JpaTransactionManager
. We eventually
activate Spring Data JPA repositories using the
@EnableJpaRepositories
annotation which
essentially carries the same attributes as the XML namespace does. If no
base package is configured it will use the one the configuration class
resides in.
Saving an entity can be performed via the
CrudRepository.save(…)
-Method. It will persist or merge the
given entity using the underlying JPA
EntityManager
. If the entity has not been
persisted yet Spring Data JPA will save the entity via a call to the
entityManager.persist(…)
-Method, otherwise the
entityManager.merge(…)
-Method will be called.
Spring Data JPA offers the following strategies to detect whether an entity is new or not:
Table 2.2. Options for detection whether an entity is new in Spring Data JPA
Id-Property inspection (default) | By default Spring Data JPA inspects the Id-Property of
the given Entity. If the Id-Property is null ,
then the entity will be assumed as new, otherwise as not
new. |
Implementing
Persistable | If an entity implements the
Persistable interface, Spring
Data JPA will delegate the new-detection to the
isNew - Method of the Entity. See the
JavaDoc
for details. |
Implementing
EntityInformation | One can customize the
EntityInformation abstraction
used in the SimpleJpaRepository
implementation by creating a subclass of
JpaRepositoryFactory and overriding the
getEntityInformation -Method
accordingly. One then has to register the custom
implementation of JpaRepositoryFactory
as a Spring bean. Note that this should be rarely necessary.
See the JavaDoc
for details. |
The JPA module supports defining a query manually as String or have it being derived from the method name.
Although getting a query derived from the method name is quite
convenient, one might face the situation in which either the method
name parser does not support the keyword one wants to use or the
method name would get unnecessarily ugly. So you can either use JPA
named queries through a naming convention (see Section 2.3.3, “Using JPA NamedQueries” for more information) or
rather annotate your query method with
@Query
(see Section 2.3.4, “Using @Query” for details).
Generally the query creation mechanism for JPA works as described in Section 1.2, “Query methods”. Here's a short example of what a JPA query method translates into:
Example 2.3. Query creation from method names
public interface UserRepository extends Repository<User, Long> { List<User> findByEmailAddressAndLastname(String emailAddress, String lastname); }
We will create a query using the JPA criteria API from this but essentially this translates into the following query:
select u from User u where u.emailAddress = ?1 and u.lastname = ?2
Spring Data JPA will do a property check and traverse nested properties as described in ???. Here's an overview of the keywords supported for JPA and what a method containing that keyword essentially translates to.
Table 2.3. Supported keywords inside method names
Keyword | Sample | JPQL snippet |
---|---|---|
And | findByLastnameAndFirstname | … where x.lastname = ?1 and x.firstname =
?2 |
Or | findByLastnameOrFirstname | … where x.lastname = ?1 or x.firstname =
?2 |
Is,Equals | findByFirstname,findByFirstnameIs,findByFirstnameEquals | … where x.firstname = 1? |
Between | findByStartDateBetween | … where x.startDate between 1? and
?2 |
LessThan | findByAgeLessThan | … where x.age < ?1 |
LessThanEqual | findByAgeLessThanEqual | … where x.age <= ?1 |
GreaterThan | findByAgeGreaterThan | … where x.age > ?1 |
GreaterThanEqual | findByAgeGreaterThanEqual | … where x.age >= ?1 |
After | findByStartDateAfter | … where x.startDate > ?1 |
Before | findByStartDateBefore | … where x.startDate < ?1 |
IsNull | findByAgeIsNull | … where x.age is null |
IsNotNull,NotNull | findByAge(Is)NotNull | … where x.age not null |
Like | findByFirstnameLike | … where x.firstname like ?1 |
NotLike | findByFirstnameNotLike | … where x.firstname not like ?1 |
StartingWith | findByFirstnameStartingWith | … where x.firstname like ?1 (parameter
bound with appended % ) |
EndingWith | findByFirstnameEndingWith | … where x.firstname like ?1 (parameter
bound with prepended % ) |
Containing | findByFirstnameContaining | … where x.firstname like ?1 (parameter
bound wrapped in % ) |
OrderBy | findByAgeOrderByLastnameDesc | … where x.age = ?1 order by x.lastname
desc |
Not | findByLastnameNot | … where x.lastname <> ?1 |
In | findByAgeIn(Collection<Age>
ages) | … where x.age in ?1 |
NotIn | findByAgeNotIn(Collection<Age>
age) | … where x.age not in ?1 |
True | findByActiveTrue() | … where x.active = true |
False | findByActiveFalse() | … where x.active = false |
IgnoreCase | findByFirstnameIgnoreCase | … where UPPER(x.firstame) =
UPPER(?1) |
Note | |
---|---|
|
Note | |
---|---|
The examples use simple |
To use XML configuration simply add the necessary
<named-query />
element to the
orm.xml
JPA configuration file located in
META-INF
folder of your classpath. Automatic
invocation of named queries is enabled by using some defined naming
convention. For more details see below.
Example 2.4. XML named query configuration
<named-query name="User.findByLastname"> <query>select u from User u where u.lastname = ?1</query> </named-query>
As you can see the query has a special name which will be used to resolve it at runtime.
Annotation configuration has the advantage of not needing another configuration file to be edited, probably lowering maintenance costs. You pay for that benefit by the need to recompile your domain class for every new query declaration.
Example 2.5. Annotation based named query configuration
@Entity @NamedQuery(name = "User.findByEmailAddress", query = "select u from User u where u.emailAddress = ?1") public class User { }
To allow execution of these named queries all you need to do is
to specify the UserRepository
as
follows:
Example 2.6. Query method declaration in UserRepository
public interface UserRepository extends JpaRepository<User, Long> { List<User> findByLastname(String lastname); User findByEmailAddress(String emailAddress); }
Spring Data will try to resolve a call to these methods to a named query, starting with the simple name of the configured domain class, followed by the method name separated by a dot. So the example here would use the named queries defined above instead of trying to create a query from the method name.
Using named queries to declare queries for entities is a valid
approach and works fine for a small number of queries. As the queries
themselves are tied to the Java method that executes them you actually
can bind them directly using the Spring Data JPA @Query
annotation rather than annotating them to the domain class. This will
free the domain class from persistence specific information and
co-locate the query to the repository interface.
Queries annotated to the query method will take precedence over
queries defined using @NamedQuery
or named queries declared
in orm.xml
.
Example 2.7. Declare query at the query method using
@Query
public interface UserRepository extends JpaRepository<User, Long> { @Query("select u from User u where u.emailAddress = ?1") User findByEmailAddress(String emailAddress); }
The query execution mechanism for manually defined queries using
@Query
allow the definition of advanced
LIKE
expressions inside the query definition.
Example 2.8. Advanced LIKE
expressions in
@Query
public interface UserRepository extends JpaRepository<User, Long> { @Query("select u from User u where u.firstname like %?1") List<User> findByFirstnameEndsWith(String firstname); }
In the just shown sample LIKE
delimiter character
%
is recognized and the query transformed into a valid
JPQL query (removing the %
). Upon query execution the
parameter handed into the method call gets augmented with the
previously recognized LIKE
pattern.
The @Query
annotation allows to
execute native queries by setting the nativeQuery
flag to
true. Note, that we currently don't support execution of pagination or
dynamic sorting for native queries as we'd have to manipulate the
actual query declared and we cannot do this reliably for native
SQL.
Example 2.9. Declare a native query at the query method using
@Query
public interface UserRepository extends JpaRepository<User, Long> { @Query(value = "SELECT * FROM USERS WHERE EMAIL_ADDRESS = ?0", nativeQuery = true) User findByEmailAddress(String emailAddress); }
By default Spring Data JPA will use position based parameter
binding as described in all the samples above. This makes query methods
a little error prone to refactoring regarding the parameter position. To
solve this issue you can use @Param
annotation to give a
method parameter a concrete name and bind the name in the query.
Example 2.10. Using named parameters
public interface UserRepository extends JpaRepository<User, Long> { @Query("select u from User u where u.firstname = :firstname or u.lastname = :lastname") User findByLastnameOrFirstname(@Param("lastname") String lastname, @Param("firstname") String firstname); }
Note that the method parameters are switched according to the occurrence in the query defined.
As of Spring Data JPA Release 1.4 we support the usage of
restricted SpEL template expressions in manually defined queries via
@Query
. Upon query execution these expressions are
evaluated against a predefined set of variables. We support the
following list of variables to be used in a manual query.
Table 2.4. Supported variables inside SpEL based query templates
Variable | Usage | Description |
---|---|---|
entityName | select x from #{#entityName} x | Inserts the entityName of the domain type associated
with the given Repository. The entityName is
resolved as follows: If the domain type has set the name
property on the @Entity annotation then it will
be used. Otherwise the simple class-name of the domain type
will be used. |
The following example demonstrates one use case for the
#{#entityName}
expression in a query string where you want
to define a repository interface with a query method with a manually
defined query. In order not to have to state the actual entity name in
the query string of a @Query
annotation one can use the
#{#entityName}
Variable.
Note | |
---|---|
The |
Example 2.11. Using SpEL expressions in Repository query methods - entityName
@Entity public class User { @Id @GeneratedValue Long id; String lastname; } public interface UserRepository extends JpaRepository<User,Long> { @Query("select u from #{#entityName} u where u.lastname = ?1") List<User> findByLastname(String lastname); }
Of course you could have just used User
in
the query declaration directly but that would require you to change the
query as well. The reference to #entityName
will pick up
potential future remappings of the User
class to
a different entity name (e.g. by using @Entity(name =
"MyUser")
.
Another use case for the #{#entityName}
expression in
a query string is if you want to define a generic repository interface
with specialized repository interfaces for a concrete domain type. In
order not to have to repeat the definition of custom query methods on
the concrete interfaces you can use the entity name expression in the
query string of the @Query
annotation in the generic
repository interface.
Example 2.12. Using SpEL expressions in Repository query methods - entityName with inheritance
@MappedSuperclass public abstract class AbstractMappedType { … String attribute } @Entity public class ConcreteType extends AbstractMappedType { … } @NoRepositoryBean public interface MappedTypeRepository<T extends AbstractMappedType> extends Repository<T, Long> { @Query("select t from #{#entityName} t where t.attribute = ?1") List<T> findAllByAttribute(String attribute); } public interface ConcreteRepository extends MappedTypeRepository<ConcreteType> { … }
In the example the interface MappedTypeRepository
is
the common parent interface for a few domain types extending
AbstractMappedType
. It also defines the generic
method findAllByAttribute(…)
which can be used
on instances of the specialized repository interfaces. If you now invoke
findByAllAttribute(…)
on
ConcreteRepository
the query being
executed will be select t from ConcreteType t where t.attribute =
?1
.
All the sections above describe how to declare queries to access a
given entity or collection of entities. Of course you can add custom
modifying behaviour by using facilities described in Section 1.3, “Custom implementations for Spring Data repositories”. As this approach is
feasible for comprehensive custom functionality, you can achieve the
execution of modifying queries that actually only need parameter binding
by annotating the query method with @Modifying
:
Example 2.13. Declaring manipulating queries
@Modifying @Query("update User u set u.firstname = ?1 where u.lastname = ?2") int setFixedFirstnameFor(String firstname, String lastname);
This will trigger the query annotated to the method as updating
query instead of a selecting one. As the
EntityManager
might contain outdated
entities after the execution of the modifying query, we do not
automatically clear it (see JavaDoc of
EntityManager
.clear()
for details) since this will effectively drop all non-flushed changes
still pending in the EntityManager
. If
you wish the EntityManager
to be cleared
automatically you can set @Modifying
annotation's clearAutomatically
attribute to
true
.
To apply JPA QueryHint
s to the
queries declared in your repository interface you can use the
QueryHints
annotation. It takes an array
of JPA QueryHint
annotations plus a
boolean flag to potentially disable the hints applied to the addtional
count query triggered when applying pagination.
Example 2.14. Using QueryHints with a repository method
public interface UserRepository extends Repository<User, Long> { @QueryHints(value = { @QueryHint(name = "name", value = "value")}, forCounting = false) Page<User> findByLastname(String lastname, Pageable pageable); }
The just shown declaration would apply the configured
QueryHint
for that actually query but
omit applying it to the count query triggered to calculate the total
number of pages.
The JPA 2.1 specification introduced support for specifiying
Fetch- and LoadGraphs that we also support via the
EntityGraph
annotation which allows to
reference a NamedEntityGraph
definition,
that can be annotated on an entity, to be used to configure the fetch
plan of the resulting query. The type (Fetch / Load) of the fetching can
be configured via the type
attribute on the
EntityGraph
annotation. Please have a
look at the JPA 2.1 Spec 3.7.4 for further reference.
Example 2.15. Defining a named entity graph on an entity.
@Entity @NamedEntityGraph(name = "GroupInfo.detail", attributeNodes = @NamedAttributeNode("members")) public class GroupInfo { // default fetch mode is lazy. @ManyToMany List<GroupMember> members = new ArrayList<GroupMember>(); … }
Example 2.16. Referencing a named entity graph definition on an repository query method.
@Repository public interface GroupRepository extends CrudRepository<GroupInfo, String> { @EntityGraph(value = "GroupInfo.detail", type = EntityGraphType.LOAD) GroupInfo getByGroupName(String name); }
The JPA 2.1 specification introduced support for calling stored
procedures via the JPA criteria query API. We Introduced the
Procedure
annotation for declaring stored
procedure metadata on a repository method.
Example 2.17. The definition of the pus1inout procedure in HSQL DB.
/; DROP procedure IF EXISTS plus1inout /; CREATE procedure plus1inout (IN arg int, OUT res int) BEGIN ATOMIC set res = arg + 1; END /;
Metadata for stored procedures can be configured via the
NamedStoredProcedureQuery
annotation on
an entity type.
Example 2.18. StoredProcedure metadata definitions on an entity.
@Entity @NamedStoredProcedureQuery(name = "User.plus1", procedureName = "plus1inout", parameters = { @StoredProcedureParameter(mode = ParameterMode.IN, name = "arg", type = Integer.class), @StoredProcedureParameter(mode = ParameterMode.OUT, name = "res", type = Integer.class) }) public class User { }
Stored procedures can be referenced from a
Repository
method in multiple ways. The
stored procedure to be called can either be defined directly via the
value
or procedureName
attribute of the
@Procedure
annotation or indirectly via
the name
attribute. If no name is configured the name of
the repository method is used as a fallback.
Example 2.19. Referencing explicitly mapped procedure with name "plus1inout" in database.
@Procedure("plus1inout")
Integer explicitlyNamedPlus1inout(Integer arg);
Example 2.20. Referencing implicitly mapped procedure with name "plus1inout"
in database via procedureName
alias.
@Procedure(procedureName = "plus1inout")
Integer plus1inout(Integer arg);
Example 2.21. Referencing explicitly mapped named stored procedure
"User.plus1IO" in
EntityManager
.
@Procedure(name = "User.plus1IO") Integer entityAnnotatedCustomNamedProcedurePlus1IO(@Param("arg") Integer arg);
Example 2.22. Referencing implicitly mapped named stored procedure
"User.plus1" in EntityManager
via
method-name.
@Procedure Integer plus1(@Param("arg") Integer arg);
JPA 2 introduces a criteria API that can be used to build queries
programmatically. Writing a criteria
you actually define the
where-clause of a query for a domain class. Taking another step back these
criteria can be regarded as predicate over the entity that is described by
the JPA criteria API constraints.
Spring Data JPA takes the concept of a specification from Eric
Evans' book "Domain Driven Design", following the same semantics and
providing an API to define such
Specification
s using the JPA criteria API.
To support specifications you can extend your repository interface with
the JpaSpecificationExecutor
interface:
public interface CustomerRepository extends CrudRepository<Customer, Long>, JpaSpecificationExecutor { … }
The additional interface carries methods that allow you to execute
Specification
s in a variety of ways.
For example, the findAll
method will return all
entities that match the specification:
List<T> findAll(Specification<T> spec);
The Specification
interface is as
follows:
public interface Specification<T> { Predicate toPredicate(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder builder); }
Okay, so what is the typical use case?
Specification
s can easily be used to build
an extensible set of predicates on top of an entity that then can be
combined and used with JpaRepository
without the need to declare a query (method) for every needed combination.
Here's an example:
Example 2.23. Specifications for a Customer
public class CustomerSpecs { public static Specification<Customer> isLongTermCustomer() { return new Specification<Customer>() { public Predicate toPredicate(Root<Customer> root, CriteriaQuery<?> query, CriteriaBuilder builder) { LocalDate date = new LocalDate().minusYears(2); return builder.lessThan(root.get(Customer_.createdAt), date); } }; } public static Specification<Customer> hasSalesOfMoreThan(MontaryAmount value) { return new Specification<Customer>() { public Predicate toPredicate(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder builder) { // build query here } }; } }
Admittedly the amount of boilerplate leaves room for improvement
(that will hopefully be reduced by Java 8 closures) but the client side
becomes much nicer as you will see below. The
Customer_
type is a metamodel type generated using
the JPA Metamodel generator (see the Hibernate
implementation's documentation for example). So the expression
Customer_.createdAt
is asuming the
Customer
having a createdAt
attribute
of type Date
. Besides that we have expressed some
criteria on a business requirement abstraction level and created
executable Specification
s. So a client
might use a Specification
as
follows:
Example 2.24. Using a simple Specification
List<Customer> customers = customerRepository.findAll(isLongTermCustomer());
Okay, why not simply create a query for this kind of data access?
You're right. Using a single Specification
does not gain a lot of benefit over a plain query declaration. The power
of Specification
s really shines when you
combine them to create new Specification
objects. You can achieve this through the
Specifications
helper class we provide to build
expressions like this:
Example 2.25. Combined Specifications
MonetaryAmount amount = new MonetaryAmount(200.0, Currencies.DOLLAR); List<Customer> customers = customerRepository.findAll( where(isLongTermCustomer()).or(hasSalesOfMoreThan(amount)));
As
you can see, Specifications
offers some glue-code
methods to chain and combine
Specification
s. Thus extending your data
access layer is just a matter of creating new
Specification
implementations and
combining them with ones already existing.
CRUD methods on repository instances are transactional by default.
For reading operations the transaction configuration readOnly
flag is set to true, all others are configured with a plain
@Transactional
so that default transaction
configuration applies. For details see JavaDoc of
Repository
. If you need to tweak transaction
configuration for one of the methods declared in
Repository
simply redeclare the method in
your repository interface as follows:
Example 2.26. Custom transaction configuration for CRUD
public interface UserRepository extends JpaRepository<User, Long> { @Override @Transactional(timeout = 10) public List<User> findAll(); // Further query method declarations }
This will cause the findAll()
method to
be executed with a timeout of 10 seconds and without the
readOnly
flag.
Another possibility to alter transactional behaviour is using a facade or service implementation that typically covers more than one repository. Its purpose is to define transactional boundaries for non-CRUD operations:
Example 2.27. Using a facade to define transactions for multiple repository calls
@Service class UserManagementImpl implements UserManagement { private final UserRepository userRepository; private final RoleRepository roleRepository; @Autowired public UserManagementImpl(UserRepository userRepository, RoleRepository roleRepository) { this.userRepository = userRepository; this.roleRepository = roleRepository; } @Transactional public void addRoleToAllUsers(String roleName) { Role role = roleRepository.findByName(roleName); for (User user : userRepository.findAll()) { user.addRole(role); userRepository.save(user); } }
This will cause call to
addRoleToAllUsers(…)
to run inside a
transaction (participating in an existing one or create a new one if
none already running). The transaction configuration at the repositories
will be neglected then as the outer transaction configuration determines
the actual one used. Note that you will have to activate
<tx:annotation-driven />
or use
@EnableTransactionManagement
explicitly
to get annotation based configuration at facades working. The example
above assumes you are using component scanning.
To allow your query methods to be transactional simply use
@Transactional
at the repository
interface you define.
Example 2.28. Using @Transactional at query methods
@Transactional(readOnly = true) public interface UserRepository extends JpaRepository<User, Long> { List<User> findByLastname(String lastname); @Modifying @Transactional @Query("delete from User u where u.active = false") void deleteInactiveUsers(); }
Typically you will want the readOnly
flag set to
true as most of the query methods will only read data. In contrast to
that deleteInactiveUsers()
makes use of the
@Modifying
annotation and overrides the
transaction configuration. Thus the method will be executed with
readOnly
flag set to false.
Note | |
---|---|
It's definitely reasonable to use transactions for read only
queries and we can mark them as such by setting the
|
To specify the lock mode to be used the
@Lock
annotation can be used on query
methods:
Example 2.29. Defining lock metadata on query methods
interface UserRepository extends Repository<User, Long> { // Plain query method @Lock(LockModeType.READ) List<User> findByLastname(String lastname); }
This method declaration will cause the query being triggered to be
equipped with the LockModeType
READ
. You can also define locking for CRUD methods by
redeclaring them in your repository interface and adding the
@Lock
annotation:
Example 2.30. Defining lock metadata on CRUD methods
interface UserRepository extends Repository<User, Long> { // Redeclaration of a CRUD method @Lock(LockModeType.READ); List<User> findAll(); }
Spring Data provides sophisticated support to transparently keep track of who created or changed an entity and the point in time this 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.
We provide @CreatedBy
,
@LastModifiedBy
to capture the user who
created or modified the entity as well as
@CreatedDate
and
@LastModifiedDate
to capture the point in
time this happened.
Example 2.31. An audited entity
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'd like to capture. For the annotations
capturing the points in time can be used on properties of type
org.joda.time.DateTime
,
java.util.Date
as well as
long
/Long
.
In case you don't 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's also a convenience base class
AbstractAuditable
which you can extend to
avoid the need to manually implement the interface methods. Be aware that
this 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.
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 of what type the properties annotated
with @CreatedBy
or
@LastModifiedBy
have to be.
Here's an example implementation of the interface using Spring
Security's Authentication
object:
Example 2.32. Implementation of AuditorAware based on Spring Security
class SpringSecurityAuditorAware implements AuditorAware<User> { public User getCurrentAuditor() { Authentication authentication = SecurityContextHolder.getContext().getAuthentication(); if (authentication == null || !authentication.isAuthenticated()) { return null; } return ((MyUserDetails) authentication.getPrincipal()).getUser(); } }
The implementation is accessing the
Authentication
object provided by Spring
Security and looks up the custom
UserDetails
instance from it that you have
created in your UserDetailsService
implementation. We're assuming here that you are exposing the domain user
through that UserDetails
implementation but
you could also look it up from anywhere based on the
Authentication
found.
Spring Data JPA ships with an entity listener that can be used to
trigger capturing auditing information. So first you have to register
the AuditingEntityListener
inside your
orm.xml
to be used for all entities in your
persistence contexts:
Note that the auditing feature requires
spring-aspects.jar
to be on the classpath.
Example 2.33. Auditing configuration orm.xml
<persistence-unit-metadata> <persistence-unit-defaults> <entity-listeners> <entity-listener class="….data.jpa.domain.support.AuditingEntityListener" /> </entity-listeners> </persistence-unit-defaults> </persistence-unit-metadata>
Now activating auditing functionality is just a matter of adding
the Spring Data JPA auditing
namespace element to
your configuration:
Example 2.34. Activating auditing using XML configuration
<jpa:auditing auditor-aware-ref="yourAuditorAwareBean" />
As of Spring Data JPA 1.5, auditing can be enabled by annotating a
configuration class with the @EnableJpaAuditing
annotation.
Example 2.35. Activating auditing via Java configuration
@Configuration @EnableJpaAuditing class Config { @Bean public AuditorAware<AuditableUser> auditorProvider() { return new AuditorAwareImpl(); } }
If you expose a bean of type
AuditorAware
to the
ApplicationContext
, the auditing
infrastructure will pick it up automatically and use it to determine the
current user to be set on domain types. If you have multiple
implementations registered in the
ApplicationContext
, you can select the
one to be used by explicitly setting the auditorAwareRef
attribute of @EnableJpaAuditing
.
Spring supports having multiple persistence units out of the box.
Sometimes, however, you might want to modularize your application but
still make sure that all these modules run inside a single persistence
unit at runtime. To do so Spring Data JPA offers a
PersistenceUnitManager
implementation that automatically
merges persistence units based on their name.
Example 2.36. Using MergingPersistenceUnitmanager
<bean class="….LocalContainerEntityManagerFactoryBean"> <property name="persistenceUnitManager"> <bean class="….MergingPersistenceUnitManager" /> </property </bean>
A plain JPA setup requires all annotation mapped entity classes
listed in orm.xml
. Same applies to XML mapping
files. Spring Data JPA provides a
ClasspathScanningPersistenceUnitPostProcessor
that gets a base package configured and optionally takes a mapping
filename pattern. It will then scan the given package for classes
annotated with @Entity
or
@MappedSuperclass
and also loads the
configuration files matching the filename pattern and hands them to the
JPA configuration. The PostProcessor has to be configured like
this
Example 2.37. Using ClasspathScanningPersistenceUnitPostProcessor
<bean class="….LocalContainerEntityManagerFactoryBean"> <property name="persistenceUnitPostProcessors"> <list> <bean class="org.springframework.data.jpa.support.ClasspathScanningPersistenceUnitPostProcessor"> <constructor-arg value="com.acme.domain" /> <property name="mappingFileNamePattern" value="**/*Mapping.xml" /> </bean> </list> </property> </bean>
Note | |
---|---|
As of Spring 3.1 a package to scan can be configured on the
|
Instances of the repository interfaces are usually created by a container, which Spring is the most natural choice when working with Spring Data. There's sophisticated support to easily set up Spring to create bean instances documented in Section 1.2.3, “Creating repository instances”. As of version 1.1.0 Spring Data JPA ships with a custom CDI extension that allows using the repository abstraction in CDI environments. The extension is part of the JAR so all you need to do to activate it is dropping the Spring Data JPA JAR into your classpath.
You can now set up the infrastructure by implementing a CDI
Producer
for the
EntityManagerFactory
and
EntityManager
:
class EntityManagerFactoryProducer { @Produces @ApplicationScoped public EntityManagerFactory createEntityManagerFactory() { return Persistence.createEntityManagerFactory("my-presistence-unit"); } public void close(@Disposes EntityManagerFactory entityManagerFactory) { entityManagerFactory.close(); } @Produces @RequestScoped public EntityManager createEntityManager(EntityManagerFactory entityManagerFactory) { return entityManagerFactory.createEntityManager(); } public void close(@Disposes EntityManager entityManager) { entityManager.close(); } }
The necessary setup can vary depending on the JavaEE environment
you run in. It might also just be enough to redeclare a
EntityManager
as CDI bean as
follows:
class CdiConfig { @Produces @RequestScoped @PersistenceContext public EntityManager entityManager; }
In this example, the container has to be capable of creating JPA
EntityManager
s itself. All the
configuration does is re-exporting the JPA
EntityManager
as CDI bean.
The Spring Data JPA CDI extension will pick up all
EntityManager
s availables as CDI beans
and create a proxy for a Spring Data repository whenever an bean of a
repository type is requested by the container. Thus obtaining an
instance of a Spring Data repository is a matter of declaring an
@Inject
ed property:
class RepositoryClient { @Inject PersonRepository repository; public void businessMethod() { List<Person> people = repository.findAll(); } }