Error in the findById of a generic class for persistence and queries using Hibernate JPA

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I have a generic class I’m using to perform queries with JPA Hibernate.

My class is like this:

public class BaseRepositoryImpl<T> implements BaseRepository<T>

The problem is that in some methods, such as the findById below, I need to explain the Type of the object. And since it is a generic type, it generates an error.

@Override
public T findById(Long id) {
    em.getTransaction().begin();
    T t = em.find(Class<T>, id);   // ERRORRRR
    em.getTransaction().commit();
    return null;
}

How I must proceed to repair that mistake?

java hibernate jpa
  • 1

    This might help: https://stackoverflow.com/a/9202329

  • It helped a little. But, I had to implement otherwise.

1 answer

0


In the generic class, you need to manually pull the value by instantiating the class.

public BaseRepositoryImpl(Class<T> entity) {
    ...
    this.entity = entity;
}

As it is working with inheritance, the classes that will make the reuse, would be implemented as follows:

public class PessoaRepositoryImpl extends BaseRepositoryImpl<Pessoa> implements PessoaRepository {

    public PessoaRepositoryImpl() {
        super(Pessoa.class);
    }

    ...

}

Inside the constructor, the super is instantiated and we can refer to the class explicitly.

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