DATA ACCESS PATTERN - Java EE Design Patterns - page 159

LISTING 12‐2: The DAO interface

package com.devchronicles.dataaccessobject;

import java.util.List;

public interface MovieDAO {
public void addMovie(Movie movie);
public Movie getMovie(int id);
public void deleteMovie(int id);
public void updateMovie(Movie movie);
public List<Movie> getAllMovies();
}

Now for the concrete implementation of the DAO interface shown in Listing 12‐3. Here you imple-
ment the CRUD operations. Notice that the constructor accepts an instance of the EntityManager .
r

This instance is associated with a persistence context that is dei ned in persistence.xml . The
EntityManager API provides create, remove, and persistence functionality as well as the ability to
create queries. Any transient i eld would not be saved or retrieved from the database so expect the
data on the transient i eld to be reset each time the object is re-created.

LISTING 12‐3: The implementation of the DAO interface

package com.devchronicles.dataaccessobject;

import java.util.List;
import javax.persistence.EntityManager;

public class MovieDAOImpl implements MovieDAO{

private EntityManager em;

public MovieDAOImpl(EntityManager em) {
this.em = em;
}

@Override
public void addMovie(Movie movie) {
em.persist(movie);
}

@Override
public Movie getMovie(int id) {
return getAllMovies().get(id);
}

@Override
public void deleteMovie(int id) {
em.remove(getMovie(id));

continues