spring+hibernate JPA

关于spring+hibernate JPA的一个例子

      通过spring配置来实现对数据库的访问和对事务的管理

简单的对一张表（table）的操作

实体类：

User.java

package domain;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;

/**
 * User generated by MyEclipse Persistence Tools
 */
@Entity
@Table(name = "user", catalog = "shopping")
@NamedQueries(value = {@NamedQuery(name = "User.findAllUsers", query = "from User")})
public class User implements java.io.Serializable {

 // Fields

 /**
  *
  */
 private static final long serialVersionUID = 2172281412405163597L;
    @Id
 @GeneratedValue(strategy=GenerationType.AUTO)
 private Integer id;

 private String name;

 private String pswd;

 private String email;

 // Constructors

 /** default constructor */
 public User() {
 }

 /** full constructor */
 public User(Integer id, String name, String pswd, String email) {
  this.id = id;
  this.name = name;
  this.pswd = pswd;
  this.email = email;
 }

 // Property accessors
 @Id
 @Column(name = "ID", unique = true, nullable = false, insertable = true, updatable = true)
 public Integer getId() {
  return this.id;
 }

 public void setId(Integer id) {
  this.id = id;
 }

 @Column(name = "NAME", unique = false, nullable = false, insertable = true, updatable = true, length = 30)
 public String getName() {
  return this.name;
 }

 public void setName(String name) {
  this.name = name;
 }

 @Column(name = "PSWD", unique = false, nullable = false, insertable = true, updatable = true, length = 45)
 public String getPswd() {
  return this.pswd;
 }

 public void setPswd(String pswd) {
  this.pswd = pswd;
 }

 @Column(name = "EMAIL", unique = false, nullable = false, insertable = true, updatable = true, length = 60)
 public String getEmail() {
  return this.email;
 }

 public void setEmail(String email) {
  this.email = email;
 }

}

 

Userdao.java (对表user的操作)

package com;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.PersistenceException;
import javax.persistence.Query;

import org.springframework.orm.jpa.JpaCallback;
import org.springframework.orm.jpa.JpaTemplate;
import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;

import domain.User;

@Repository
public class Userdao {

 private EntityManagerFactory entityManagerFactory;

 public Userdao() {
 }

 protected JpaTemplate getJpaTemplate() {
  return new JpaTemplate(this.entityManagerFactory);
 }

 @Transactional
 // 声明为事务
 public void createUser(User user) {
  final JpaTemplate jpaTemplate = getJpaTemplate();
  jpaTemplate.persist(user);
 }

 @Transactional
 // 声明为事务
 public void updateAndsaveUser(User user) {
  final JpaTemplate jpaTemplate = getJpaTemplate();
  user = jpaTemplate.merge(user);
  System.out.println("修改完成");
 }

 @Transactional
 public void deleteUser(User user) {// 注意与deleteUserById()方法的比较
  final JpaTemplate jpaTemplate = getJpaTemplate();// 下面为什么没有用user
  // =jpaTemplate.merge(user);
  // 是因为下面的查找和删除都在一个事务中，user一直处于managed状态
  user = jpaTemplate.merge(user); // change bean from detacthed to
  // managed;
  jpaTemplate.remove(user);
 }

 public User findUserById(Integer id) {
  final JpaTemplate jpaTemplate = getJpaTemplate();
  return jpaTemplate.find(User.class, id);
 }

 @Transactional
 // 声明事务
 public boolean deleteAllUsers() {
  final JpaTemplate jpaTemplate = getJpaTemplate();
  return (Boolean) jpaTemplate.execute(new JpaCallback() {

   public Object doInJpa(EntityManager em) throws PersistenceException {
    Query q = em.createNativeQuery("Delete from User");
    if (q.executeUpdate() == 0)
     return Boolean.TRUE;
    else
     return Boolean.FALSE;
   }
  });
 }

 public List findAllUsers() {
  final JpaTemplate jpaTemplate = getJpaTemplate();
  return jpaTemplate.findByNamedQuery("User.findAllUsers");
 }

 @Transactional
 // 事务声明 删除操作必须在事务中才能完成
 public boolean deleteUserById(Integer id) {
  User user = null;
  final JpaTemplate jpaTemplate = getJpaTemplate();
  user = jpaTemplate.find(User.class, id);
  if (user != null) {
   jpaTemplate.remove(user);
   System.out.println("删除用户：" + user.getName() + "(id=" + user.getId()
     + ")");
   return true;
  } else {
   System.out.println("无法删除用户(id=" + id + ")");
   return false;
  }

 }

 public void setEntityManagerFactory(
   EntityManagerFactory entityManagerFactory) {
  this.entityManagerFactory = entityManagerFactory;
 }
}

persistence.xml (持久化单元)

<?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="entityManagerFactory"
  transaction-type="RESOURCE_LOCAL">
  <provider>org.hibernate.ejb.HibernatePersistence</provider>
  <class>domain.User</class>
  <properties>
   <property name="hibernate.connection.driver_class"
    value="com.mysql.jdbc.Driver" />
   <property name="hibernate.connection.url"
    value="jdbc:mysql://localhost:3306/shopping?useUnicode=true&amp;characterEncoding=GB2312" />
   <property name="hibernate.connection.username" value="root" />
   <property name="hibernate.connection.password" value="1024" />
   <property name="show_sql" value="true" />
   <property name="hibernate.Dialect"
    value="org.hibernate.dialect.MySQLDialect" />
  </properties>
 </persistence-unit>
</persistence>

ApplicationContext.xml（Spring的一些配置）

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xmlns:aop="http://www.springframework.org/schema/aop"
 xmlns:tx="http://www.springframework.org/schema/tx"
 xsi:schemaLocation="http://www.springframework.org/schema/beans
 http://www.springframework.org/schema/beans/spring-beans-2.0.xsd    
 http://www.springframework.org/schema/tx
 http://www.springframework.org/schema/tx/spring-tx-2.0.xsd   
    http://www.springframework.org/schema/aop
    http://www.springframework.org/schema/aop/spring-aop-2.0.xsd">
 <bean id="entityManagerFactory"
  class="org.springframework.orm.jpa.LocalEntityManagerFactoryBean">
  <property name="persistenceUnitName"
   value="entityManagerFactory" />
 </bean>
 <bean
  class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor" />

<!--   事务管理配置 -->
 <bean id="myTxManager"
  class="org.springframework.orm.jpa.JpaTransactionManager">
  <property name="entityManagerFactory"
   ref="entityManagerFactory" />
 </bean>
 <tx:annotation-driven transaction-manager="myTxManager"></tx:annotation-driven>

 <bean id="userdao" class="com.Userdao">
  <property name="entityManagerFactory"
   ref="entityManagerFactory" />
 </bean>

</beans>

 

测试类

package com;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import domain.User;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {

 /**
  * @param args
  */

 public static void main(String[] args) {
  ApplicationContext ctx = new ClassPathXmlApplicationContext(
    "ApplicationContext.xml");
  Userdao dao = (Userdao) ctx.getBean("userdao");
  // System.out.println("姓名："+dao.getUser().getName());
  // System.out.println("年龄："+dao.getUser().getAge());
  /*
   * dao.deleteUserById(1); dao.deleteUserById(2); dao.deleteUserById(3);
   */
  // System.out.println(dao.deleteAllUsers());
//   User user1 = new User(4,"lb","1235","[e-mail]");
//   User user2 = new User(5,"hjp","1236","[e-mail]");
//   User user3 = new User(6,"zrq","1237","[e-mail]");
//   dao.createUser(user1);
//   dao.createUser(user2);
//   dao.createUser(user3);
  User user11 = dao.findUserById(8);
  if (user11 != null)
   {System.out.println("姓名： " + user11.getName() + "(id="
     + user11.getId() + ");");
  dao.deleteUser(user11);}
  System.out.println("<----------------------------------->");
  User user = dao.findUserById(1);
  user.setName("yyq");
  user.setEmail("[e-mail]");
  dao.updateAndsaveUser(user);
  List<User> userlist = new ArrayList<User>();
  userlist = dao.findAllUsers();
  Iterator item = userlist.iterator();
  int i = 0;
  while (item.hasNext()) {
   i++;
   System.out.println(i + ". 姓名：" + ((User) item.next()).getName());
  }
 }

}

要注意的就是在Userdao.java中对User的cud等操作的事务性处理，事务通过@Transactional来声明，那么在ApplicationContext.xml中配置的事务管理器会自动把这个操作当作事务来处理。

 

JPA是持久化的标准，需要provider。现在支持JPA的ORM包有多种。Netbeans自带Toplink，如果想使用ORM框架的一些高级的功能，可以使用Hibernate作为JPA的实现。

       使用Hibernate作为JPA的实现，需要在官网下载core、annotation、entityManager包。一般支持Hibernate的IDE都会带有core包，那么只需一下这些jar就可以：

       ejb3-persistence.jar        //创建实体时可以使用jdk1.6带的注释功能

hibernate-annotations.jar

hibernate-commons-annotations.jar

hibernate-entitymanager.jar    //创建持久性单元需要这个jar

javassist.jar

jboss-archive-browsing.jar

将这些jar放到类路径就可以创建持久性单元persisitence.xml。

<?xml version="1.0" encoding="UTF-8"?>

<persistence version="1.0" 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 http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">

<persistence-unit name="JavaApplication14PU" transaction-type="RESOURCE_LOCAL">

    <provider>org.hibernate.ejb.HibernatePersistence</provider>

    <class>model.JH</class>

    <properties>

      <property name="hibernate.connection.username" value="root"/>

      <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>

      <property name="hibernate.connection.password" value=" 123"/>

      <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/news"/>

 

      <property name="hibernate.hbm2ddl.auto" value="update"/>

    <property name="show_sql" value="true"/>

    </properties>

</persistence-unit>

</persistence>

 

其实这个就和hibernate.cfg.xml一样，用于管理持久层的配置。

不过写法和hibernate.cfg.xml有一些区别。

在hibernate.cfg.xml我们可以这样写：

<property name="show_sql">true</true>

但是在persistence.xml里面，我们得在value里面写：

<property name="show_sql" value="true"/>

 

之后建立实体就可以使用我们的Annotation了，不用再使用mapping文件了。

 

如果要使用到hibernate的高级功能，只需要在这个persistence.xml里面添加就可以了，例如我想添加二级缓存还有查询缓存，可以添加：

    <!-- 配置缓存插件 -->  

    <property name="hibernate.cache.provider_class" value="org.hibernate.cache.EhCacheProvider"/>

   

    <!-- 开启二级缓存 -->

<property name="hibernate.cache.use_second_level_cache" value="true"/>

 

而且当实体需要使用缓存的时候，我们只需要加上这个Annotation：

@Cache(usage = CacheConcurrencyStrategy.READ_WRITE)

public class MyModel{}

 

这相当于在mapping文件里面添加：

<cache usage="read-only"/>