package ejava.examples.webtier.jpa;
   
   import java.util.Iterator;
   import java.util.List;
   import java.util.Map;
   
   import javax.persistence.EntityManager;
   import javax.persistence.Query;
   
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  import ejava.examples.webtier.bo.Student;
  import ejava.examples.webtier.dao.StudentDAO;
  import ejava.examples.webtier.dao.StudentDAOException;
  
  public class StudentJPADAO implements StudentDAO {
      Log log = LogFactory.getLog(StudentJPADAO.class);
  
      public Student create(Student student) throws StudentDAOException {
          try {
              JPAUtil.getEntityManager().persist(student);
          }
          catch (Throwable ex) {
              throw new StudentDAOException(ex);
          }
          return student;
      }
  
      @SuppressWarnings("unchecked")
      public List<Student> find(int index, int count) throws StudentDAOException {
          try {
          return JPAUtil.getEntityManager().createQuery(
                  "select s from Student s " +
                  "").setFirstResult(index)
                     .setMaxResults(count)
                     .getResultList();
          }
          catch (Throwable ex) {
              throw new StudentDAOException(ex);
          }
      }
  
      @SuppressWarnings("unchecked")
      public List<Student> find(
              String name, Map<String, Object> args, int index, int count) 
          throws StudentDAOException {
          try {
              log.debug("named query:" + name + 
                      ", index=" + index + ", count=" + count);
              Query query = JPAUtil.getEntityManager().createNamedQuery(name);
              if (query != null && args!=null) {
                  for(Iterator<String> itr=args.keySet().iterator();
                      itr.hasNext();) {
                      String key = itr.next();
                      Object value = args.get(key);
                      query.setParameter(key, value);
                      log.debug("key=" + key + ", value=" + value);
                  }
              }
              return query.setFirstResult(index)
                          .setMaxResults(count)
                          .getResultList();
          }
          catch (StudentDAOException ex) {
              throw new StudentDAOException(ex);
          }
      }
  
      public List<Student> find(String name, int index, int count) 
          throws StudentDAOException {
          return find(name, null, index, count);
      }
  
      public Student get(long id) throws StudentDAOException {
          try {
              return JPAUtil.getEntityManager().find(Student.class, id);
          }
          catch (StudentDAOException ex) {
              throw new StudentDAOException(ex);
          }
      }
  
      public Student remove(Student student) throws StudentDAOException {
          try {
              JPAUtil.getEntityManager().remove(student);
              return student;
          }
          catch (StudentDAOException ex) {
              throw new StudentDAOException(ex);
          }
      }
  
      public Student update(Student student) throws StudentDAOException {
          try {
              EntityManager em = JPAUtil.getEntityManager();
              return em.merge(student);
          }
          catch (StudentDAOException ex) {
             throw new StudentDAOException(ex);
         }
     }
 }