如何将枚举作为通用参数传递

Question

I'm implementing basic CRUD for REST service based on DAO injected via CDI. It's gonna work with multiple injections and I wanna pass the type of DAO from class that extends GenericRest . I followed this tutorial.

http://www.javacodegeeks.com/2013/06/java-ee-cdi-programmatic-dependency-disambiguation-example-injection-point-inspection.html

And get workable code:

GenericREST.java

public abstract class GenericREST {
    @Inject
    @DAOProducer
    @DAOType(DAO.COMMENT)
    private GenericDAO dao;
    ...
}

GenericDAO.java

public interface GenericDAO<T, PK extends Serializable> {
    public T create(T t);
    public T read(final PK id);
    public T update(T t);
    public void delete(final PK id);
}

It works well when I'm setting @DAOType as described above. But I wanna somehow select DAO by passing its' type from extended class.

Is there any way of doing it? Or maybe there is much easier way?

Answer 1

Assuming you use CDI instances, you can do something like this:

@Inject
@DAOProducer
private Instance<GenericDAO<?,?>> genericDaoInst;

protected GenericDAO<?,?> getDao(DAO dao) {
    return genericDaoInst.select(new DAOTypeLiteral(dao)).get();
}

then somewhere in your code...

GenericDAO<?,?> dao = getDao(DAO.COMMENT);