Configuration

You have to add the following configuration to you spring beans configuration file. You have to specified a new repository factory class. We will develop the class later.

<jpa:repositories base-package="example.borislam.dao"
factory-class="example.borislam.data.springData.DefaultRepositoryFactoryBean/>

Just develop an interface extending JpaRepository. You should remember to annotate it with @NoRepositoryBean.

@NoRepositoryBean
public interface GenericRepository <T, ID extends Serializable>
 extends JpaRepository<T, ID> {   
}

Next step is to develop the customized base repository class. You can see that I just one property (i.e. springDataRepositoryInterface) inside this customized base repository. I just want to get more control on the behaviour of the customized behaviour of the repository interface. I will show how to add more features of this base repository class in the next post.

@SuppressWarnings("unchecked")
@NoRepositoryBean
public class GenericRepositoryImpl<T, ID extends Serializable>
 extends SimpleJpaRepository<T, ID>  implements GenericRepository<T, ID> , Serializable{
  
 private static final long serialVersionUID = 1L;
 
 static Logger logger = Logger.getLogger(GenericRepositoryImpl.class);
  
    private final JpaEntityInformation<T, ?> entityInformation;
    private final EntityManager em;
    private final DefaultPersistenceProvider provider;
      
    private  Class<?> springDataRepositoryInterface;
 public Class<?> getSpringDataRepositoryInterface() {
  return springDataRepositoryInterface;
 }
 
 public void setSpringDataRepositoryInterface(
   Class<?> springDataRepositoryInterface) {
  this.springDataRepositoryInterface = springDataRepositoryInterface;
 }
 
 /**
     * Creates a new {@link SimpleJpaRepository} to manage objects of the given
     * {@link JpaEntityInformation}.
     *
     * @param entityInformation
     * @param entityManager
     */
    public GenericRepositoryImpl (JpaEntityInformation<T, ?> entityInformation, EntityManager entityManager , Class<?> springDataRepositoryInterface) {
     super(entityInformation, entityManager);
     this.entityInformation = entityInformation;
     this.em = entityManager;
     this.provider = DefaultPersistenceProvider.fromEntityManager(entityManager);
     this.springDataRepositoryInterface = springDataRepositoryInterface;
     }
 
    /**
     * Creates a new {@link SimpleJpaRepository} to manage objects of the given
     * domain type.
     *
     * @param domainClass
     * @param em
     */
    public GenericRepositoryImpl(Class<T> domainClass, EntityManager em) {
        this(JpaEntityInformationSupport.getMetadata(domainClass, em), em, null); 
    }
  
    public <S extends T> S save(S entity)
    {    
        if (this.entityInformation.isNew(entity)) {
            this.em.persist(entity);
            flush();
            return entity;
          }
  entity = this.em.merge(entity);
  flush();
        return entity;
    }
 
    
    public T saveWithoutFlush(T entity)
    {
      return
       super.save(entity);
    }
     
    public List<T> saveWithoutFlush(Iterable<? extends T> entities)
    {
     List<T> result = new ArrayList<T>();
  if (entities == null) {
   return result;
  }
 
  for (T entity : entities) {
   result.add(saveWithoutFlush(entity));
  }
  return result;
    }
} 

As a simple example here, I just override the default save method of the SimpleJPARepository. The default behaviour of the save method will not flush after persist. I modified to make it flush after persist. On the other hand, I add another method called saveWithoutFlush() to allow developer to call save the entity without flush.  

Define Custom repository factory bean

The last step is to create a factory bean class and factory class to produce repository based on your customized base repository class.

public class DefaultRepositoryFactoryBean <T extends JpaRepository<S, ID>, S, ID extends Serializable>
  extends JpaRepositoryFactoryBean<T, S, ID> {
    /**
     * Returns a {@link RepositoryFactorySupport}.
     *
     * @param entityManager
     * @return
     */
    protected RepositoryFactorySupport createRepositoryFactory(
            EntityManager entityManager) {
 
        return new DefaultRepositoryFactory(entityManager);
    }
}
 
 
/**
 *
 * The purpose of this class is to override the default behaviour of the spring JpaRepositoryFactory class.
 * It will produce a GenericRepositoryImpl object instead of SimpleJpaRepository.
 *
 */
public  class DefaultRepositoryFactory extends JpaRepositoryFactory{
     
 private final EntityManager entityManager;
    private final QueryExtractor extractor;
 
 
    public DefaultRepositoryFactory(EntityManager entityManager) {
     super(entityManager);
        Assert.notNull(entityManager);
        this.entityManager = entityManager;
        this.extractor = DefaultPersistenceProvider.fromEntityManager(entityManager);
    }
     
    @SuppressWarnings({ "unchecked", "rawtypes" })
    protected <T, ID extends Serializable> JpaRepository<?, ?> getTargetRepository(
            RepositoryMetadata metadata, EntityManager entityManager) {
 
        Class<?> repositoryInterface = metadata.getRepositoryInterface();
        
        JpaEntityInformation<?, Serializable> entityInformation =
                getEntityInformation(metadata.getDomainType());
 
        if (isQueryDslExecutor(repositoryInterface)) {
            return new QueryDslJpaRepository(entityInformation, entityManager);
        } else {
            return new GenericRepositoryImpl(entityInformation, entityManager, repositoryInterface); //custom implementation
        }
    }
  
    @Override
    protected Class<?> getRepositoryBaseClass(RepositoryMetadata metadata) {
 
        if (isQueryDslExecutor(metadata.getRepositoryInterface())) {
            return QueryDslJpaRepository.class;
        } else {
            return GenericRepositoryImpl.class;
        }
    }
     
    /**
     * Returns whether the given repository interface requires a QueryDsl
     * specific implementation to be chosen.
     *
     * @param repositoryInterface
     * @return
     */
    private boolean isQueryDslExecutor(Class<?> repositoryInterface) {
 
        return QUERY_DSL_PRESENT
                && QueryDslPredicateExecutor.class
                        .isAssignableFrom(repositoryInterface);
    }  
}

Conclusion

You could now add more features to base repository class. In your program, you could now create your own repository interface extending GenericRepository instead of JpaRepository.

	
public interface MyRepository <T, ID extends Serializable>
  extends GenericRepository <T, ID> {
   void someCustomMethod(ID id); 
}

In next post, I will show you how to add hibernate filter features to this GenericRepository.