JPA HelloWorld 非常适合初学

package jpadao; import java.util.List; import java.util.logging.Level; import javax.persistence.EntityManager; /** * Data access object (DAO) for domain model class Myuser. * * @see jpadao.Myuser * @author MyEclipse Persistence Tools */ public class MyuserDAO implements IMyuserDAO { // property constants public static final String USERNAME = "username"; public static final String PASSWORD = "password"; private EntityManager getEntityManager() { return EntityManagerHelper.getEntityManager(); } public void save(Myuser transientInstance) { EntityManagerHelper.log("saving Myuser instance", Level.INFO, null); try { getEntityManager().persist(transientInstance); EntityManagerHelper.log("save successful", Level.INFO, null); } catch (RuntimeException re) { EntityManagerHelper.log("save failed", Level.SEVERE, re); throw re; } } public void delete(Myuser persistentInstance) { EntityManagerHelper.log("deleting Myuser instance", Level.INFO, null); try { getEntityManager().remove(persistentInstance); EntityManagerHelper.log("delete successful", Level.INFO, null); } catch (RuntimeException re) { EntityManagerHelper.log("delete failed", Level.SEVERE, re); throw re; } } public Myuser update(Myuser detachedInstance) { EntityManagerHelper.log("updating Myuser instance", Level.INFO, null); try { Myuser result = getEntityManager().merge(detachedInstance); EntityManagerHelper.log("update successful", Level.INFO, null); return result; } catch (RuntimeException re) { EntityManagerHelper.log("update failed", Level.SEVERE, re); throw re; } } public Myuser findById(Integer id) { EntityManagerHelper.log("finding Myuser instance with id: " + id, Level.INFO, null); try { Myuser instance = getEntityManager().find(Myuser.class, id); return instance; } catch (RuntimeException re) { EntityManagerHelper.log("find failed", Level.SEVERE, re); throw re; } } @SuppressWarnings("unchecked") public List<Myuser> findByProperty(String propertyName, Object value) { EntityManagerHelper.log("finding Myuser instance with property: " + propertyName + ", value: " + value, Level.INFO, null); try { String queryString = "select model from Myuser model where model." + propertyName + "= :propertyValue"; return getEntityManager().createQuery(queryString).setParameter( "propertyValue", value).getResultList(); } catch (RuntimeException re) { EntityManagerHelper.log("find by property name failed", Level.SEVERE, re); ; throw re; } } public List<Myuser> findByUsername(Object username) { return findByProperty(USERNAME, username); } public List<Myuser> findByPassword(Object password) { return findByProperty(PASSWORD, password); } @SuppressWarnings("unchecked") public List<Myuser> findAll() { EntityManagerHelper.log("finding all Myuser instances", Level.INFO, null); try { String queryString = "select model from Myuser model"; return getEntityManager().createQuery(queryString).getResultList(); } catch (RuntimeException re) { EntityManagerHelper.log("find all failed", Level.SEVERE, re); ; throw re; } } }