Hibernate温习(8)--使用JPA
这次讲的JPA前一篇文章都有所介绍，这里呢就是结合hibernate.cfg.xml来讲讲，怎么用JPA进行CURD操作，类似于Hibernate的session进行CURD操作
hibernate.cfg.xml
<?xml version="1.0" encoding="utf-8" ?><!DOCTYPE hibernate-configuration PUBLIC"-//Hibernate/Hibernate Configuration DTD 3.0//EN""http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"><hibernate-configuration><session-factory><property name="connection.driver_class">com.mysql.jdbc.Driver</property><property name="connection.url">jdbc:mysql:///test</property><property name="connection.username">root</property><property name="connection.password">root</property><property name="dialect">org.hibernate.dialect.MySQLDialect</property><property name="connection.isolation">2</property><property name="show_sql">true</property><property name="hbm2ddl.auto">update</property><property name="format_sql">true</property><!-- mapping类声明--><mapping /></session-factory></hibernate-configuration>
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?JPA使用要求SRC的META-INF下要有persistence.xml
<?xml version="1.0" encoding="UTF-8"?><!-- example of a default persistence.xml --><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="xkkjpa"><properties><property name="hibernate.ejb.cfgfile" value="/hibernate.cfg.xml" /></properties></persistence-unit></persistence>
?Hibernate这里用到的实体类映射是采用的是注解方式，其实就是JPA的注解
User.java
package com.javacrazyer.domain;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.Table;@Entity@Table(name="user")public class User {@Id@GeneratedValue(strategy=GenerationType.AUTO)private Long id;private String name;private String pwd;public Long getId() {return id;}public void setId(Long id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getPwd() {return pwd;}public void setPwd(String pwd) {this.pwd = pwd;}public String toString(){return "id=" + id + ",name=" + name + ",pwd=" + pwd;}}?UserDao.java
package com.javacrazyer.dao;import java.util.List;import javax.persistence.EntityManager;import com.javacrazyer.common.JPAUtil;import com.javacrazyer.domain.PageModel;import com.javacrazyer.domain.User;public class UserDao {public void add(User user){EntityManager em = JPAUtil.getEntityManager();em.getTransaction().begin();em.persist(user);em.getTransaction().commit();em.close();}@SuppressWarnings("unchecked")public List<User> findAll(){EntityManager em = JPAUtil.getEntityManager();em.getTransaction().begin();//JPAQLList<User> users = em.createQuery("from User").getResultList();em.getTransaction().commit();em.close();return users;}@SuppressWarnings("unchecked")public PageModel<User> findByPager(int pageNo, int pageSize){PageModel<User> pm = new PageModel<User>();EntityManager em = JPAUtil.getEntityManager();em.getTransaction().begin();Long count = (Long)em.createQuery("select count(o) from User o").getSingleResult();if(count != null){List<User> users = em.createQuery("from User") .setFirstResult((pageNo - 1) * pageSize) .setMaxResults(pageSize) .getResultList();pm.setRecordCount(count.intValue());pm.setDatas(users);}em.getTransaction().commit();em.close();return pm;}public User findById(Long id){EntityManager em = JPAUtil.getEntityManager();em.getTransaction().begin();//User user = em.find(User.class, id); //相当于Hibernate的get()方法User user = em.getReference(User.class, id); //相当于Hibernate的load()方法em.getTransaction().commit();em.close();return user;}public void update(User user){EntityManager em = JPAUtil.getEntityManager();em.getTransaction().begin();user = em.merge(user);em.getTransaction().commit();em.close();}public void delete(User user){EntityManager em = JPAUtil.getEntityManager();em.getTransaction().begin();em.remove(user);em.getTransaction().commit();em.close();}}?PageModel.java
package com.javacrazyer.domain;import java.util.List;/** * 分页组件(包含当前页结果数据列表和总记录数) * 注意，它不是持久化实体类 * */public class PageModel<T> {private int recordCount;private List<T> datas;public int getRecordCount() {return recordCount;}public void setRecordCount(int recordCount) {this.recordCount = recordCount;}public List<T> getDatas() {return datas;}public void setDatas(List<T> datas) {this.datas = datas;}}?JPAUtil.java
package com.javacrazyer.common;import javax.persistence.EntityManager;import javax.persistence.EntityManagerFactory;import javax.persistence.Persistence;public class JPAUtil { private static EntityManagerFactory factory; static { //加载src/META-INF/PERSISTENTCE.XML ,根据配置文件中的键加载 factory = Persistence.createEntityManagerFactory("xkkjpa"); } private JPAUtil() {} public static EntityManager getEntityManager() { return factory.createEntityManager(); }}?测试代码
package com.javacrazyer.dao.test;import org.junit.Assert;import org.junit.Test;import com.javacrazyer.dao.UserDao;import com.javacrazyer.domain.PageModel;import com.javacrazyer.domain.User;public class UserDaoTest {private UserDao dao = new UserDao();@Testpublic void testAdd(){User user = new User();user.setName("xxxx");user.setPwd("12345678790");dao.add(user);Assert.assertNotNull(user.getId());}@Testpublic void testFindByPager(){PageModel<User> pm = dao.findByPager(2, 1);for(User user : pm.getDatas()){System.out.println(user);}}}?根据JPA对实体类进行CRUD的操作特点与Hibernate的处理方式做下对比
?Hibernate处理方式为：通过SessionFactory获得session，然后通过session的各种方法进行CURD操作
?JPA的处理方式为：通过EntityManagerFactory获得entityManager，然后通过entityManager的各种方法进行CURD
Hibernate是SessionFacotory sessionFactory=config.buidSessionFacotory()
JPA是EntityManagerFactory entityManagerFactory=Persistence.createEntityManagerFactory("xkkjpa");
hibernate是Session session=sessionFactory.openSesion()
JPA是EntityManager entityManager=factory.createEntityManager()
session的增删改查为save,delete,update,merge,createQuery()
entityManager的增删改为persist,remove,merge,createQuery
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