JPA+Hibernate3 CRUD(增删改查操作)

JPA与Hibernate3结合的CRUD(增删改查操作)

package com.archie.test;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

import com.archie.model.User;

/**
 * CRUD操作测试
 * @author archie2010
 * since 2011-4-19下午22:13:26
 */
public class CrudTest {
    public static void addUser(){
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("jpaTest");
        // EntityManager相当于Hibernate中session
        EntityManager em = factory.createEntityManager();
        em.getTransaction().begin();
        // 保存(持久化)方法
        em.persist(new User("Tom"));
        em.getTransaction().commit();
        em.close();
        factory.close();
    }
    /**
     * 删除
     */
    public static void deleteUser(){
          EntityManagerFactory factory = Persistence.createEntityManagerFactory("jpaTest");
            EntityManager em = factory.createEntityManager();
           
            em.getTransaction().begin();
            User user = em.find(User.class, 1);
            em.remove(user);
            em.getTransaction().commit();
            
            em.close();
            factory.close();
    }
    //=======================查询
    /**
     * find方法相当于Hibernate中的get方法，
     * getReference方法相当于Hibernate中的load方法，具有延迟加载的作用；
     * 当查找的对象不存在时，find的方法返回null值，
     * 而getReference方法则抛出异常javax.persistence.EntityNotFoundException
     */
    
    /**
     * 查询byFind
     */
    public static void findUserByFind(){
        
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("jpaTest");
        EntityManager em = factory.createEntityManager();
       
        //Find方法相当于Hibernate中的get方法
        User user = em.find(User.class, 1);
        
        System.out.println(user.getUserName());
        
        em.close();
        factory.close();
    }
    /**
     * 查询ByReference
     */
    public static void findUserByReference(){
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("jpaTest");
        EntityManager em = factory.createEntityManager();
        
        //getReference方法相当于Hibername中的load方法，具有延迟加载的功能
        User user = em.getReference(User.class, 1);
        
        System.out.println(user.getUserName());
        
        em.close();
        factory.close();
    }
    /**
     * 更新
     */
    public static void updateUser(){
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("jpaTest");
        EntityManager em = factory.createEntityManager();
       
        em.getTransaction().begin();
        User user = em.find(User.class, 1);
        user.setUserName("tom_new");
        //相当于hibernate将游离状态下的数据更新到数据库中 
        em.getTransaction().commit();
        
        em.close();
        factory.close();
    }
    /**
     * 更新
     * 将游离状态下的数据更新到数据库中 
     */
    public static void updateUserByMerge(){
         EntityManagerFactory factory = Persistence.createEntityManagerFactory("jpaTest");
            EntityManager em = factory.createEntityManager();
            
            em.getTransaction().begin();
            User user = em.find(User.class, 1);
            //把实体管理器中的实体变成游离状态
            em.clear();
            user.setUserName("tom_Merge");
            //把游离状态下的更新同步到数据库中
            em.merge(user);
            em.getTransaction().commit();
            
            em.close();
            factory.close();
    }
    /**
     * main方法测试
     * @param args
     */
    public static void main(String[] args) {
        /*findUserByFind();
        findUserByReference();
        updateUserByMerge();
        deleteUser();
        */
        addUser();
    }
}