Question

I’m trying to create a generic DAO in order to avoid having more or less the same code in many separate DAOs.

My problem is that in the following lines of code:

private BaseDAOImpl<Artist> baseDAOArtist = new BaseDAOImpl<>(Artist.class);
private BaseDAOImpl<ArtistRelation> baseDAOArtistRelation = new BaseDAOImpl<>(ArtistRelation.class);

The first one seems to be skipped.

An excerpt of the BaseDAOImpl:

public class BaseDAOImpl<T> implements BaseDAO<T> {

    private Class<T> entity;
    private DAOFactory daoFactory = Config.getInstance().getDAOFactory();
    private static String SQL_FIND_BY_ID;

    public BaseDAOImpl(Class entity) {
        this.entity = entity;
        SQL_FIND_BY_ID = "SELECT * FROM VIEW_" + entity.getSimpleName() + " WHERE id = ?";        
    }
}

Is it not possible to instantiate multiple objects this way?

Answer 1

Yes. It’s not clear what you mean by “The first one seems to be skipped.” but it could be that your using a static value for “SQL_FIND_BY_ID”? As at the moment:

private BaseDAOImpl<Artist> baseDAOArtist = new BaseDAOImpl<>(Artist.class);

Creates two instance variables and sets the value of SQL_FIND_BY_ID then:

private BaseDAOImpl<ArtistRelation> baseDAOArtistRelation = new BaseDAOImpl<>(ArtistRelation.class);

Creates two new instance variables and will change the value “SQL_FIND_BY_ID” for both instances.