openJpa的应用，感觉还可以

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?上面是我写这个程序的项目结构图

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配置文件persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
??? xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
??? xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
??? http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd" version="1.0">
???
?<persistence-unit name="lushuifa" transaction-type="RESOURCE_LOCAL">
??<provider>org.apache.openjpa.persistence.PersistenceProviderImpl</provider>
??<class>com.lushuifa.po.User</class>
? ??<properties>
???<property name = "openjpa.ConnectionDriverName" value = "com.mysql.jdbc.Driver"/>
???<property name = "openjpa.ConnectionURL" value = "jdbc:mysql://localhost:3306/test"/>
???<property name = "openjpa.ConnectionUserName" value = "root"/>
???<property name = "openjpa.ConnectionPassword" value = "lushuifa"/>
???<property name = "openjpa.jdbc.SynchronizeMappings" value = "buildSchema(ForeignKeys=true)"/>
???<!--显示SQL执行语句-->
??????????? <property name="openjpa.Log" value="SQL=TRACE"/>
?? ?</properties>
?</persistence-unit>
</persistence>

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实体bean User.java

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package com.lushuifa.po;

import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class User implements Serializable
{
?/**/
??? private static final long serialVersionUID = 1L;
??? private int userId;
??? private String userName;
?
??? @Id
??? @GeneratedValue(strategy=GenerationType.AUTO)
??? public int getUserId()
??? {
??? ?return userId;
??? }
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??? public void setUserId(int userId)
??? {
??? ?this.userId = userId;
??? }
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??? public String getUserName()
??? {
??? ?return userName;
??? }
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??? public void setUserName(String userName)
??? {
??? ?this.userName = userName;
??? }
}

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dao层，UserDao.java 数据库访问对象

package com.lushuifa.dao;

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

import com.lushuifa.po.User;

public class UserDao
{
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?private EntityManager entityManager = getEntityManager();
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?// 拿到EntityManager
?public EntityManager getEntityManager()
?{
??EntityManager em = null;
??try
??{
???EntityManagerFactory emf = Persistence.createEntityManagerFactory("lushuifa");
???em = emf.createEntityManager();
??}
??catch (Exception e)
??{
???System.out.println("获取EntityManager失败了！原因如下：" + e);
??}
??return em;
?}
?
?// 添加用户的方法
?public void addUser(User user)
?{
??System.out.println(this.entityManager);
??try
??{
???this.entityManager.getTransaction().begin();
??
???this.entityManager.persist(user);
???this.entityManager.getTransaction().commit();
???System.out.println("添加用户成功！");
??}
??catch (Exception e)
??{
???System.out.println("添加用户失败，原因如下：");
???e.printStackTrace();
??}
?}
?
?//查询用户的方法
?public User findUserById(int id){
??User user = null;
??try
??????? {
???user =? this.entityManager.find(User.class,id);
??????? }
??????? catch (Exception e)
??????? {
??????? ?System.out.println("查询用户有误，原因如下：" + e);
??????? }
??????? return user;
?}
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?public static void main(String[] args)
?{
??// 测试是否拿到entitymanager
??EntityManagerFactory emf = Persistence.createEntityManagerFactory("lushuifa");
??EntityManager em = emf.createEntityManager();
??System.out.println(em);
?}
}

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单元测试类

package com.lushuifa.dao;

import org.junit.Test;

import com.lushuifa.po.User;

public class UserDaoTest
{
?private UserDao userDao = new UserDao();
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?@Test
?public void testAddUser()
?{
??User user = new User();
??user.setUserName("刘德华");
??this.userDao.addUser(user);
?}
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?@Test
?public void testFindUserById()
?{
??User user = this.userDao.findUserById(1);
??System.out.println("查出来的名字是："+user.getUserName());
?}
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}

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测试效果

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