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:

<?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 1.3.3, “Creating repository instances”. Beyond that it activates persistence exception translation for all beans annotated with @Repository to let exceptions being thrown by the JPA presistence providers be converted into Spring's DataAccessException hierarchy.

The Spring Data JPA repositories support cannot only be activated through an XML namespace but also using an annotation through 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.

The JPA module supports defining a query manually as String or have it being derived from the method name.

Generally the query creation mechanism for JPA works as described in Section 1.3, “Query methods”. Here's a short example of what a JPA query method translates into:

public interface UserRepository extends Repository<User, Long> {

  List<User> findByEmailAddressAndLastname(String emailAddress, String lastname);
}

select u from User u where u.emailAddress = ?1 and u.lastname = ?2

	Note
	In and NotIn also take any subclass of Collection as parameter as well as arrays or varargs. For other syntactical versions of the very same logical operator check Appendix B, Repository query keywords.

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.

public interface UserRepository extends JpaRepository<User, Long> {

  @Query("select u from User u where u.emailAddress = ?1")
  User findByEmailAddress(String emailAddress);
}

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:

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);
}

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 1.4, “Custom implementations”. 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:

@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 automatically clear it (see JavaDoc of EntityManager.clear() for details). This will effectively drop all non-flushed changes still pending in the EntityManager. If you don't wish the EntityManager to be cleared automatically you can set @Modifying annotation's clearAutomatically attribute to false;

To apply JPA QueryHints 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.

public interface UserRepository extends Repository<User, Long> {

  @QueryHints(value = { @QueryHint(name = "name", value = "value")}, 
              forCounting = false)
  Page<User> findByLastname(String lastname, Pageable pageable);
}

To allow your query methods to be transactional simply use @Transactional at the repository interface you define.

@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();
}

Note

It's definitely reasonable to use transactions for read only queries and we can mark them as such by setting the readOnly flag. This will not, however, act as check that you do not trigger a manipulating query (although some databases reject INSERT and UPDATE statements inside a read only transaction). The readOnly flag instead is propagated as hint to the underlying JDBC driver for performance optimizations. Furthermore, Spring will perform some optimizations on the underlying JPA provider. E.g. when used with Hibernate the flush mode is set to NEVER when you configure a transaction as readOnly which causes Hibernate to skip dirty checks (a noticeable improvement on large object trees).

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.

class Customer {

  @CreatedBy
  private User user;
  
  @CreatedDate
  private DateTime createdDate;

  // … further properties omitted
}

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();
  }
}

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:

<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:

<jpa:auditing auditor-aware-ref="yourAuditorAwareBean" />

As you can see you have to provide a bean that implements the AuditorAware interface which looks as follows:

public interface AuditorAware<T, ID extends Serializable> {

    T getCurrentAuditor();
}

Usually you will have some kind of authentication component in your application that tracks the user currently working with the system. This component should be AuditorAware and thus allow seamless tracking of the auditor.

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.

<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

<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 LocalContainerEntityManagerFactoryBean directly to enable classpath scanning for entity classes. See the JavaDoc for details.

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 1.3.3, “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:

class EntityManagerFactoryProducer {

  @Produces
  @ApplicationScoped
  public EntityManagerFactory createEntityManagerFactory() {
    return Persistence.createEntityManagerFactory("my-presistence-unit");
  }

  public void close(@Disposes EntityManagerFactory entityManagerFactory) {
    entityManagerFactory.close();
  }
}

The Spring Data JPA CDI extension will pick up all EntityManagers 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 @Injected property:

class RepositoryClient {

  @Inject
  PersonRepository repository;

  public void businessMethod() {

    List<Person> people = repository.findAll();
  }
}