package ejava.examples.daoex.jpa;
   
   import javax.persistence.EntityManager;
   import javax.persistence.TypedQuery;
   
   import org.slf4j.Logger;
   import org.slf4j.LoggerFactory;
   
   import ejava.examples.daoex.bo.Author;
  import ejava.examples.daoex.dao.AuthorDAO;
  import ejava.examples.daoex.dao.DAOException;
  
  /**
   * This class implements a DAO using javax.persistence.EntityManager. Most
   * of the work of mapping the objects to the database is being performed in
   * either the @Entity class or in a orm.xml descriptor file. The caller of 
   * this object must manage the transaction scope. The EntityManager is being
   * injected into the DAO at the start of the overall transaction.
   */
  public class JPAAuthorDAO implements AuthorDAO {
      @SuppressWarnings("unused") 
      private static final Logger logger = LoggerFactory.getLogger(JPAAuthorDAO.class);
      private EntityManager em;
      
      /*
       * This methos is not in the DAO interface and must be injected at a 
       * point where we know the DAO's implementation class.
       */
      public void setEntityManager(EntityManager em) {
          this.em = em;
      }
      
      /* (non-Javadoc)
       * @see ejava.examples.dao.jpa.AuthorDAO#create(ejava.examples.dao.domain.Author)
       */
      public void create(Author author) {
          em.persist(author);
      }
      
      /* (non-Javadoc)
       * @see ejava.examples.dao.jpa.AuthorDAO#get(long)
       */
      public Author get(long id) {
          return em.find(Author.class, id);
      }
      
      /* (non-Javadoc)
       * @see ejava.examples.dao.jpa.AuthorDAO#getByQuery(long)
       */
      public Author getByQuery(long id) {
          TypedQuery<Author> query = em.createQuery("select a from jpaAuthor a where id=:id", Author.class)
          		            .setParameter("id", id);
          return query.getSingleResult();
      }
      
      /* (non-Javadoc)
       * @see ejava.examples.dao.jpa.AuthorDAO#update(ejava.examples.dao.domain.Author)
       */
      public Author update(Author author) throws DAOException {
          Author dbAuthor = em.find(Author.class, author.getId());
          if (dbAuthor!=null) {
              dbAuthor.setFirstName(author.getFirstName());
              dbAuthor.setLastName(author.getLastName());
              dbAuthor.setSubject(author.getSubject());
              dbAuthor.setPublishDate(author.getPublishDate());
              return dbAuthor;
          } else {
              throw new DAOException("unable to locate author to update");
          }
      }
  
      /* (non-Javadoc)
       * @see ejava.examples.dao.jpa.AuthorDAO#updateByMerge(ejava.examples.dao.domain.Author)
       */
      public Author updateByMerge(Author author) {
          return em.merge(author);
      }
      
      /* (non-Javadoc)
       * @see ejava.examples.dao.jpa.AuthorDAO#remove(ejava.examples.dao.domain.Author)
       */
      public void remove(Author author) {
          em.remove(author);
      }
  }