Adding Custom Functionality to JPA Repositories - Spring Data - page 79

Let's call this interface BaseRepository . Its source code is given as follows:

@NoRepositoryBean
public interface BaseRepository<T, ID extends Serializable> extends
JpaRepository<T, ID>, QueryDslPredicateExecutor<T> {

public T deleteById(ID id) throws NotFoundException;
}

Implementing the base repository interface
Next we have to write an implementation of the BaseRepository<T, ID> interface.
This process includes the following steps:

1. Create a class that implements the BaseRepository<T, ID> interface and

extends the QueryDslJpaRepository<T, ID> class. This ensures that the
class has access to the methods provided by the JpaRepository<T, ID>
interface and that Querydsl can be used.

2. Add a constructor that is used to simply pass the needed information

forward to the superclass.

3. Implement the deleteById() method. First, this method obtains the deleted

entity. If an entity is not found, this method throws NotFoundException .
Otherwise this method deletes the found entity and returns the deleted entity.

The source code of the created GenericBaseRepository class is given as follows:

public class GenericBaseRepository<T, ID extends Serializable> extends
QueryDslJpaRepository<T, ID> implements BaseRepository<T, ID> {

public GenericBaseRepository(JpaEntityInformation<T, ID>
entityMetadata, EntityManager entityManager) {
super(entityMetadata, entityManager);
}

@Override
public T deleteById(ID id) throws NotFoundException {
T deleted = findOne(id);
if (deleted == null) {
throw new NotFoundException();