#Autowired does not work in SimpleJpaRepository extension - spring-data

Question

When trying to override SimpleJpaRepository, adding other beans via #Autowired does not work. How can beans be injected in this case? Here is an implementation:
public class BaseDAO<T, ID extends Serializable>
extends SimpleJpaRepository<T, ID>
implements IDAO<T, ID> {
#Autowired
private SomeBean someBean; // NULL!
}

Answer 1

Instances of BaseDAO are not Spring-managed beans in themselves and therefore autowiring through #Autowired will not work out-of-the-box. Dependencies therefore need to be injected into BaseDAO instances.
Step 1: Have a Spring ApplicationContext available somewhere
#Component
class SpringContext implements ApplicationContextAware {
private static ApplicationContext CONTEXT;
public void setApplicationContext(final ApplicationContext context) throws BeansException {
CONTEXT = context;
}
public static ApplicationContext getContext() { return CONTEXT; }
}
This will be required to autowire the dependencies for the custom repository implementation at the time of repository creation.
Step 2: Extend SimpleJpaRepository
class BaseDAO<T, ID extends Serializable>
extends SimpleJpaRepository<T, ID> {
#Autowired
private Dependency dependency;
}
Step 3: Autowire dependencies through a JpaRepositoryFactoryBean
class ExtendedJPARepositoryFactoryBean<R extends JpaRepository<T, ID>, T, ID extends Serializable>
extends JpaRepositoryFactoryBean<R, T, ID> {
private static class ExtendedJPARepositoryFactory<T, ID extends Serializable> extends JpaRepositoryFactory {
public ExtendedJPARepositoryFactory(final EntityManager entityManager) {
super(entityManager);
}
protected Class<?> getRepositoryBaseClass(final RepositoryMetadata metadata) {
return isQueryDslExecutor(metadata.getRepositoryInterface())
? QueryDSLJPARepository.class
// Let your implementation be used instead of SimpleJpaRepository.
: BaseDAO.class;
}
protected <T, ID extends Serializable> SimpleJpaRepository<?, ?> getTargetRepository(
RepositoryInformation information, EntityManager entityManager) {
// Let the base class create the repository.
final SimpleJpaRepository<?, ?> repository = super.getTargetRepository(information, entityManager);
// Autowire dependencies, as needed.
SpringContext.getContext()
.getAutowireCapableBeanFactory()
.autowireBean(repository);
// Return the fully set up repository.
return repository;
}
}
protected RepositoryFactorySupport createRepositoryFactory(EntityManager entityManager) {
return new ExtendedJPARepositoryFactory(entityManager);
}
}
Step 4a: Configure Spring Data JPA to use your factory bean (XML configuration)
<jpa:repositories base-package="org.example.jpa"
factory-class="org.example.jpa.ExtendedJPARepositoryFactoryBean"/>
Step 4b: Configure Spring Data JPA to use your factory bean (Java configuration)
#EnableJpaRepositories(repositoryFactoryBeanClass = ExtendedJPARepositoryFactoryBean.class)

Answer 2

In order to let Spring know that it needs to inject something inside your DAO you need to annotate it with #Component.
You can read more about this here: http://docs.spring.io/autorepo/docs/spring-boot/current/reference/html/using-boot-spring-beans-and-dependency-injection.html.