JPA1之java(helloword)

最新推荐文章于 2025-08-11 14:43:21 发布

原创最新推荐文章于 2025-08-11 14:43:21 发布 · 117 阅读

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#java #数据库

本文详细介绍如何使用Hibernate框架进行数据库操作，包括配置文件persistence.xml的设置、实体类Person的设计及JUnit测试类的编写，涵盖增删改查等核心功能。

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1.上面的包除了persistence.xml不需要外,还有mysql-connector-java-5.1.8-bin.jar这个是根据自已的数据库驱动;

2.根据第二张图自已找;

3.类结构图(persistence.xml必须在META-INF下,好像官方是这么说的)

1.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="easier" transaction-type="RESOURCE_LOCAL" ><!-- 本地事务 -->
      <properties>
         <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect"/>
         <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
         <property name="hibernate.connection.username" value="root"/>
         <property name="hibernate.connection.password" value="123456"/>
         <property name="hibernate.connection.url" value="jdbc:mysql://127.0.0.1:3306/easier?useUnlcode=true&amp;characterEncoding=UTF-8"/>
         <property name="hibernate.max_fetch_depth" value="3"/>
         <property name="hibernate.show_sql" value="true"/>
         <property name="hibernate.hbm2ddl.auto" value="update"/>
         <!-- hibernate.hbm2ddl.auto
			validate             	加载hibernate时，验证创建数据库表结构
 			create                      每次加载hibernate先删除表，重新创建数据库表结构
 			create-drop        	加载hibernate先删除表后创建，退出是删除表结构
 			update                	加载hibernate自动更新数据库结构  
 		-->
        
      </properties>
     
   </persistence-unit>
</persistence>

2.Person类/**

 * 
 */
package cn.easier.bean;

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

/**
 * @author Administrator
 * 
 */
@Entity
public class Person {
	@Id @GeneratedValue
	private Integer id;

	private String name;

	public Person() {}

	/**
	 * @param id
	 * @param name
	 */
	public Person(String name) {

		this.name = name;
	}

	public Integer getId() {
		return id;
	}

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

	public String getName() {
		return name;
	}

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

}

3.junit测试类

/**
 * 
 */
package cn.easier.test;


import java.util.List;

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

import org.junit.BeforeClass;
import org.junit.Test;

import cn.easier.bean.Person;

/**
 * @author Administrator
 *
 */
public class PersonTest {
	private static EntityManagerFactory factory=null;
	private static EntityManager em=null;
	/**
	 * @throws java.lang.Exception
	 */
	@BeforeClass
	public static void setUpBeforeClass() throws Exception {
		
		factory = Persistence.createEntityManagerFactory("easier");
		em = factory.createEntityManager();
	}
	
	@Test public void save(){
		
		
	
		em.getTransaction().begin();	//开始事务
		Person person=new Person("李四");
		em.persist(person);		//保存对象
		
		em.getTransaction().commit();
		em.close();
		factory.close();
		
	}
	@Test public void delete(){
		Integer id=1;
		Person person = em.find(Person.class, id);  
		if(person!=null){
			em.getTransaction().begin();	//开始事务
			em.remove(person);
			em.getTransaction().commit();
		}
		em.close();
		factory.close();
		
	}
	@Test public void update(){
		Integer id=2;
		Person person=new Person();
		person.setId(id);	//原来的id=2的name=李四
		person = em.find(Person.class, person.getId());  
		person.setName("张三");			//更新名字
		if(person!=null){
			
			em.getTransaction().begin();	//开始事务
			em.merge(person);
			em.getTransaction().commit();
		}
		
		
		em.close();
		factory.close();
		
		
	}
	@Test public void getPerson(){
		Integer id=1;
		Person person = em.find(Person.class, id);  
		em.close();
		factory.close();
		System.out.println("id:\t"+person.getId()+"\tname:\t"+person.getName());
	}
	
	@SuppressWarnings("unchecked")
	@Test public void getList(){
		
		// 这不是“真正”SQL，而是类似sql的东西，称之为EJBQL 、JPQL
		List<Person> list=(List<Person>)em.createQuery("from Person").getResultList();
		if(list!=null&&list.size()>0){
			
			for(Person person:list){
				
				System.out.println("id:\t"+person.getId()+"\tname:\t"+person.getName());
			}
		}
		em.close();
		factory.close();
	}

}

  http://blog.youkuaiyun.com/itera/article/details/6092244 //JPQL学习