JPA初体验_MySQL

 1 <?xml version="1.0" encoding="UTF-8"?> 2 <persistence version="2.0" 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  5             http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"> 6              7     <!-- 为持久化单元取名为 myJPA --> 8     <persistence-unit name="myJPA" transaction-type="RESOURCE_LOCAL"> 9         <properties>10             <!--配置Hibernate方言 -->11             <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect"></property>12             <!--配置数据库驱动 -->13             <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"></property>14             <!--配置数据库用户名 -->15             <property name="hibernate.connection.username" value="root"></property>16             <!--配置数据库密码 -->17             <property name="hibernate.connection.password" value="root"></property>18             <!--配置数据库url -->19             <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/jpa?useUnicode=true&characterEncoding=UTF-8"></property>20             <!--设置外连接抓取树的最大深度 -->21             <property name="hibernate.max_fetch_depth" value="3"></property>22             <!--自动输出schema创建DDL语句 -->23             <property name="hibernate.hbm2ddl.auto" value="update"></property>    24         </properties>25     </persistence-unit>26             27 </persistence>

 1 package com.cndatacom.jpa.entity; 2  3 import javax.persistence.Column; 4 import javax.persistence.Entity; 5 import javax.persistence.GeneratedValue; 6 import javax.persistence.Id; 7 import javax.persistence.Table; 8  9 @Entity10 @Table(name="t_user")11 public class User {12     13     /**14      * 主键15      */16     @Id17     @GeneratedValue18     private Long id;19     20     /**21      * 名字22      */23     @Column(name="name")24     private String name;25     26     /**27      * 密码28      */29     @Column(name="password")30     private String password;31 32     public Long getId() {33         return id;34     }35 36     public void setId(Long id) {37         this.id = id;38     }39 40     public String getName() {41         return name;42     }43 44     public void setName(String name) {45         this.name = name;46     }47 48     public String getPassword() {49         return password;50     }51 52     public void setPassword(String password) {53         this.password = password;54     }55     56 }

 1 package com.cndatacom.jpa.test; 2  3 import javax.persistence.EntityManager; 4 import javax.persistence.EntityManagerFactory; 5 import javax.persistence.Persistence; 6  7 import org.junit.After; 8 import org.junit.Before; 9 import org.junit.Test;10 11 import com.cndatacom.jpa.entity.User;12 13 14 public class TestJPA {15     16     EntityManagerFactory emf = null;17     18     @Before19     public void before() {20         //根据在persistence.xml中配置的persistence-unit name 创建EntityManagerFactory21         emf = Persistence.createEntityManagerFactory("myJPA");22     }23     24     /**25      * 添加用户26      */27     @Test28     public void addUser() {29         30         //创建一个用户31         User user = new User();32         user.setName("叶开");33         user.setPassword("yekai");34         35         //创建实体管理器对象36         EntityManager em = emf.createEntityManager();37         //开启事务38         em.getTransaction().begin();39         //持久化对象40         em.persist(user);41         //提交事务42         em.getTransaction().commit();43         //关闭EntityManager44         em.close();45     }46     47     /**48      * 修改用户49      */50     @Test51     public void modifyUser() {52         EntityManager em = emf.createEntityManager();53         em.getTransaction().begin();54         //查找id为1的User55         User user = em.find(User.class, 1L);//User 的主键id为Long型56         user.setName("李坏");57         //进行更新58         em.merge(user);59         em.getTransaction().commit();60         em.close();61     }62     63     /**64      * 删除用户65      */66     @Test67     public void deleteUser() {68         EntityManager em = emf.createEntityManager();69         em.getTransaction().begin();70         //查找id为1的User71         User user = em.find(User.class, 1L);//User 的主键id为Long型72         //进行删除73         em.remove(user);74         em.getTransaction().commit();75         em.close();76     }77     78     /**79      * 关闭EntityManagerFactory80      */81     @After82     public void after() {83         if(null != emf) {84             emf.close();85         }86     }87 88 }