JPA+Hibernate 3.3 学习小结——第一个JPA程序

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所需要的最小的jar包(注意：jar包所在路径不能含有空格或中文)

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-->hibernate3.jar
hibernate-cglib-repack-2.1_3.jar
slf4j-api-1.5.2.jar
javassist-3.4.GA.jar
jta-1.1.jar
antlr-2.7.6.jar
commons-collections-3.1.jar
dom4j-1.6.1.jar
ejb3-persistence.jar
hibernate-annotations.jar
hibernate-commons-annotations.jar
hibernate-entitymanager.jar
log4j.jar
slf4j-log4j12.jar

创建实例类

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-->package com.hujuan.bean;

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

@Entity
//默认情况下表名称是根据实体类名称创建的，name可以修改表名称
@Table(name="person_table")
public class Person {

    private Integer id;
    private String userName;

    public Person(){
    }

    public Person(String userName) {
        this.userName = userName;
    }
    //主键生成策略@GeneratedValue(strategy=GenerationType.AUTO),
    //值为AUTO表示根据数据库由Hibernate自动选择生成策略，也可以省略写@GeneratedValue
    //值为IDENTITY表示主键自增长
    //值为SEQUENCE表示主键采用序列的方式
    //值为TABLE各个数据库都通用，但效率较低
    @Id  @GeneratedValue
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getUserName() {
        return userName;
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }
}

注意：因为采用的是Hibernate所以必须有一个空的构造函数

JPA的配置文件

JPA规范要求配置文件在类路径的META-INF目录下放置名称为固定的的，即persistence.xml

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--><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="jpa" transaction-type="RESOURCE_LOCAL">
     <properties>
              
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect"/>    
         <property name="hibernate.hbm2ddl.auto" value="update"/>
         <property name="hibernate.connection.driver_class" value="org.gjt.mm.mysql.Driver"/>
         <property name="hibernate.connection.username" value="root"/>
         <property name="hibernate.connection.password" value="root"/>
         <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/jpadb"/>
      </properties>
   </persistence-unit>
</persistence>

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-->package com.hujuan.test;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import org.junit.BeforeClass;
import org.junit.Test;
import com.hujuan.bean.Person;
public class PersonTest {
    @BeforeClass
    public static void setUpBeforeClass() throws Exception {
    }
     @Test
    public void save(){
//EntityManagerFactory相当于Hibernate中的sessionFactory
//Persistence.createEntityManagerFactory("jpa")与配置文件中的持久化单元名称必须相同
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("jpa");
//EntityManager相当于Hibernate中session
        EntityManager em = factory.createEntityManager();
        em.getTransaction().begin();
        //保存(持久化)方法
        em.persist(new Person("Tom"));
        em.getTransaction().commit();
        em.close();
        factory.close();
    }
}