jpa注解

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2016-07 ( 2)
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hibernate

1、加入jpa所需要的包

直接把hibernate中lib/required中的所有包放进去以及连接oracle数据库的架包。

2、写实体类（如问题类）

package com.chinasofti.jpa.entity;

import java.util.Date;
import java.util.HashSet;
import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinTable;
import javax.persistence.ManyToMany;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

import org.hibernate.annotations.GenericGenerator;

@Entity  //声明这是一个实体类
@Table(name = "t_question")  //声明表与对应的表名
public class Question
{
    @Id
    @GenericGenerator(name = "uuid", strategy = "uuid")//用hibernate包中提供的uuid生成策略
    @GeneratedValue(generator = "uuid")
    @Column(name = "id")
    private String id;
    
    @Column(name = "title")//表中的列，若与表的列名相同，name可以省略
    private String title;
    
    @Column(name = "content")
    private String content;
    
    @Column(name = "questionTime")
    private Date questionTime;
    
    @Column(name = "endTime")
    private Date endTime;
    
    @Column(name = "award")
    private int award;
    
    @Column(name = "flag")
    private int flag;
    
    @Column(name = "praiseNums")
    private int praiseNums;
    
    @Column(name = "opposeNums")
    private int opposeNums;
    
    @ManyToOne  //多对一的配置
    @JoinColumn(name = "userId")  //对应表中的列
    private User user = new User();
    
     @ManyToMany(cascade=CascadeType.ALL)   //多对多的配置，cascade为级联类型
     @JoinTable(name="t_question_tag",   //对应的中间表名
     joinColumns=@JoinColumn(name="questionId"),  //在中间表中对应的列名
     inverseJoinColumns=@JoinColumn(name="tagId"))  //另一多表对应的列名
     private Set<Tag> tags=new HashSet<Tag>();
    
    public String getId()
    {
        return id;
    }
    
    public void setId(String id)
    {
        this.id = id;
    }
    
    public String getTitle()
    {
        return title;
    }
    
    public void setTitle(String title)
    {
        this.title = title;
    }
    
    public String getContent()
    {
        return content;
    }
    
    public void setContent(String content)
    {
        this.content = content;
    }
    
    public Date getQuestionTime()
    {
        return questionTime;
    }
    
    public void setQuestionTime(Date questionTime)
    {
        this.questionTime = questionTime;
    }
    
    public Date getEndTime()
    {
        return endTime;
    }
    
    public void setEndTime(Date endTime)
    {
        this.endTime = endTime;
    }
    
    public int getAward()
    {
        return award;
    }
    
    public void setAward(int award)
    {
        this.award = award;
    }
    
    public int getPraiseNums()
    {
        return praiseNums;
    }
    
    public void setPraiseNums(int praiseNums)
    {
        this.praiseNums = praiseNums;
    }
    
    public int getOpposeNums()
    {
        return opposeNums;
    }
    
    public void setOpposeNums(int opposeNums)
    {
        this.opposeNums = opposeNums;
    }
    
    public User getUser()
    {
        return user;
    }
    
    public void setUser(User user)
    {
        this.user = user;
    }
    
    public int getFlag()
    {
        return flag;
    }
    
    public void setFlag(int flag)
    {
        this.flag = flag;
    }
     public Set<Tag> getTags()
     {
     return tags;
     }
     public void setTags(Set<Tag> tags)
     {
     this.tags = tags;
     }
}

3、写配置文件（persistence.xml）

在src目录下创建一个文件夹，名字为META-INF，别改动名字，因为默认读取名为META-INF的文件夹下的persistence.xml，不然找不到persistence.xml文件

<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_2_0.xsd"
	version="2.0">

       <!-- Name属性用于定义持久化单元的名字 (name必选,空值也合法);   
              transaction-type 指定事务类型(可选)     -->
	<persistence-unit name="jpa" transaction-type="RESOURCE_LOCAL">

		<properties>
                       <!-- 加载数据驱动 -->
			<property name="javax.persistence.jdbc.driver" value="oracle.jdbc.driver.OracleDriver" />
                        <!--加载url -->
			<property name="javax.persistence.jdbc.url" value="jdbc:oracle:thin:@localhost:1521:ORCL" />
                        <!-- 用户名 -->
			<property name="javax.persistence.jdbc.user" value="jung" />
                         <!-- 密码 -->
			<property name="javax.persistence.jdbc.password" value="jung" />
                        <!-- 方言 -->
			<property name="hibernate.dialect" value="org.hibernate.dialect.Oracle10gDialect" />
                        <!-- 是否显示sql语句 -->
			<property name="hibernate.show_sql" value="true" />
		</properties>

	</persistence-unit>
</persistence>

4、写个工具类

package com.chinasofti.jpa.util;

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

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

public class HibernateUtil
{
    private static EntityManagerFactory factory;
    
    static{
    	//使用静态代码块：代码必须在项目启动的时候就执行
    	//创建工厂，“jpa”为persistence.xml中的name
        factory=Persistence.createEntityManagerFactory("jpa");             
    }
    
    public static EntityManagerFactory getFactory()
    {
        return factory;
    }
    
    public static EntityManager getManager()
    {
        EntityManager em=factory.createEntityManager();
        return em;
    }
    
    //添加
    public static  <T> void add(T t)
    {
        EntityManager em=getManager();
        EntityTransaction et=em.getTransaction();//事务
        et.begin();//开启事务
        em.persist(t);
        et.commit();//提交事务
    }
    
    //修改
    public static <T> void update(T t) {
        EntityManager em=getManager();
        EntityTransaction et=em.getTransaction();
        et.begin();
        em.merge(t);
        et.commit();
    }
    
    //删除
    public static <T> void delete(Class<T> c, String id) 
    {
        EntityManager em=getManager();
        EntityTransaction et=em.getTransaction();
        et.begin();
        em.remove(em.find(c, id));
        et.commit();
    }
    
    //根据id查询
    public static <T> T query(Class<T> c, String id) 
    {
        EntityManager em=getManager();
        EntityTransaction et=em.getTransaction();
        et.begin();
        T t=em.find(c, id);
        et.commit();
        return t;
    }
    
    //查询全部
    @SuppressWarnings("all")
    public static <T> List<T> queryAll(Class<T> c) 
    {
        EntityManager em=getManager();
        EntityTransaction et=em.getTransaction();
        et.begin();       
        List<T> list=em.createQuery("from  "+c.getSimpleName()).getResultList();
        et.commit();
        return list;
    }
}

5、写个DAO层

package com.chinasofti.jpa.dao;

import java.util.List;

import com.chinasofti.jpa.entity.Question;
import com.chinasofti.jpa.util.HibernateUtil;


public class QuestionDao
{
    //添加
    public void addQuestion(Question question)
    {
        HibernateUtil.add(question);
    }
    
    //修改
    public void updateQuestion(Question question)
    {
        HibernateUtil.update(question);
    }
    
    //删除
    public void delQuestion(String id)
    {
        HibernateUtil.delete(Question.class, id);
    }
    
    //根据id查询
    public Question queryQuestion(String id)
    {
        return HibernateUtil.query(Question.class, id);
    }
    
    //查询全部
    public List<Question> queryAllQuestions()
    {
        return HibernateUtil.queryAll(Question.class);
    }
}

6、写个测试类（需要导入junit包）

package com.chinasofti.jpa.test;

import java.util.Calendar;
import java.util.Date;
import java.util.List;
import java.util.Set;

import org.junit.Before;
import org.junit.Test;

import com.chinasofti.jpa.dao.QuestionDao;
import com.chinasofti.jpa.entity.Question;
import com.chinasofti.jpa.entity.Tag;


public class TestQuestion
{
    private QuestionDao questionDao;
    
    @Before 
    public void before()
    {
    	//每测试一个方法时都会实例一次
        questionDao=new QuestionDao();
    }
    
    @Test     
    public void addQuestion() //添加
    {
        Question question=new Question();
        question.setTitle("问题2333");
        question.setContent("问题详细信息23333");
        question.setFlag(1);
        question.setQuestionTime(new Date());
        Calendar c = Calendar.getInstance();
        c.add(Calendar.DATE, 15); //表示当前时间的15天后
        question.setEndTime(c.getTime());

         //多对一添加
        question.getUser().setId("2c848f82555301360155530138a80000");
        
        //多对多添加标签表
        Tag tag1=new Tag();
        tag1.setName("java");
        Tag tag2=new Tag();
        tag2.setName("oracle");
        
        question.getTags().add(tag1);
        question.getTags().add(tag2);
        
        questionDao.addQuestion(question);
    }
    
    @Test   //删除
    public void delQuestion(){
        questionDao.delQuestion("2c848f9f5558a9ec015558a9f2670000");
        
    }
    
    @Test   // 根据id查询
    public void queryQuestion()
    {
        Question questions=questionDao.queryQuestion("2c848f9f5557df17015557df19ae0000");
        System.out.println(questions.getContent()+","+questions.getId());
        
    }
    
    @Test    //查询全部
    public void queryAllQuestion()
    {
        List<Question> list=questionDao.queryAllQuestions();
        for (Question question : list)
        {
            System.out.println(question.getId()+","+question.getContent());
        }
    }
    
    @Test   //多对多级联查询
    public void query()
    {
        Question question= questionDao.queryQuestion("2c848f9f5557de7e015557de811d0000");
        Set<Tag> set=question.getTags();
        for (Tag tag : set)
        {
            System.out.println(tag.getId());
        }
    }
}

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2016-07-19 11:24
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