JPA Hibernate应用实例

1.配置文件:persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
    <persistence-unit name="TestJPA" transaction-type="RESOURCE_LOCAL">
    
        <!-- JAP实现的提供者
        1.如果只有一个提供者,可以不写 -->
        <provider>org.hibernate.ejb.HibernatePersistence</provider>
        
        <class>com.hanqi.dao.JPANews</class>
    
        <properties>
        
            <!-- 数据库连接 -->
            <property name="javax.persistence.jdbc.url" value="jdbc:oracle:thin:@localhost:1521:orcl"/>
            <property name="javax.persistence.jdbc.user" value="test"/>
            <property name="javax.persistence.jdbc.password" value="test"/>
            <property name="javax.persistence.jdbc.driver" value="oracle.jdbc.OracleDriver"/>
            
            <!-- JPA提供者的配置 -->
            <!-- 数据库方言 -->
            <property name="hibernate.dialect" value="org.hibernate.dialect.Oracle10gDialect"/>
            <!-- sql语句/调试 -->
            <property name="hibernate.show_sql" value="true" />
            <property name="hibernate.format_sql" value="true" />
             <!--  自动建表(正向工程)方式 -->
            <property name="hibernate.hbm2ddl.auto" value="update" />
            
        </properties>
    
    </persistence-unit>
</persistence>

2.编写实体类:JPANews.java

package com.hanqi.dao;

import java.util.Date;

import javax.persistence.*;
@NamedQuery(name="cx",query="from JPANews n where n.id = ?")
@Table(name="JPA_News")//类与表之间的映射关系
@Entity //实体类
public class JPANews {
    
    private Integer id;
    private String title;
    private String contant;
    private Date createdate;
    private String author;
    
    @GeneratedValue(strategy=GenerationType.AUTO)//主键生成策略
    @Id//指定主键
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    
    @Basic
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    public String getContant() {
        return contant;
    }
    public void setContant(String contant) {
        this.contant = contant;
    }
    
    /**
     * @return the createdate
     */
    @Column(name="CREATEDATE")
    @Basic 
    public Date getCreatedate() {
        return createdate;
    }
    /**
     * @param createdate the createdate to set
     */
    public void setCreatedate(Date createdate) {
        this.createdate = createdate;
    }
    /**
     * @return the author
     */
    public String getAuthor() {
        return author;
    }
    /**
     * @param author the author to set
     */
    public void setAuthor(String author) {
        this.author = author;
    }
    
    @Override
    @Transient
    public String toString() {
        return "News [id=" + id + ", title=" + title + ", contant=" + contant + ", createdate=" + createdate + "]";
    }

}

3.测试用例TestJPA.java

package com.hanqi.dao;

import static org.junit.Assert.*;

import java.util.Date;
import java.util.List;

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

import org.junit.*;
import org.junit.Test;

public class TestJPA {
    EntityManagerFactory entityManagerFactory = null;
    EntityManager entityManager = null;
    EntityTransaction transaction = null;
    
    @Before
    public void init()
    {
        //1. 创建 EntitymanagerFactory
        String persistenceUnitName = "TestJPA";

        entityManagerFactory = 
                Persistence.createEntityManagerFactory(persistenceUnitName);
        

        //2. 创建 EntityManager. 类似于 Hibernate 的 SessionFactory
        entityManager = entityManagerFactory.createEntityManager();
        
        //3. 开启事务
        transaction = entityManager.getTransaction();
        transaction.begin();
    }
    
    @After
    public void destory()
    {
        //5. 提交事务
        transaction.commit();
        
        //6. 关闭 EntityManager
        entityManager.close();
        
        //7. 关闭 EntityManagerFactory
        entityManagerFactory.close();
    }

    @Test
    public void testjpa()
    {
        
        //数据操作
        JPANews jn = new JPANews();
        
        jn.setTitle("标题");
        jn.setAuthor("作者");
        jn.setContant("内容");
        jn.setCreatedate(new Date());
//        
//        entityManager.persist(jn);//保存
        JPANews jn2 = entityManager.merge(jn);//saveOrUpdate
        
        
        
        System.out.println(jn);
        System.out.println(jn2);//从瞬时状态转变为持久化状态jpa是创建一个新对象将旧对象信息拷贝到新对象中

//        JPANews jpan = entityManager.find(JPANews.class, 41);//立即加载
//        
//        jpan.setTitle("新的标题123");
//        
//        entityManager.flush();//提交语句
//        System.out.println(jpan);
//        //延迟加载
//        JPANews jpan2 = entityManager.getReference(JPANews.class, 42);
//        
//        System.out.println("id="+jpan2.getId());
//        System.out.println("标题="+jpan2.getTitle());
//        
//        entityManager.remove(jpan2);//删除
        
    }
    
    @Test
    public void testjpql()
    {
        //JPQL语句
        String jpql = "from JPANews n where n.id = ?";
        
        Query q = entityManager.createQuery(jpql);
        
//        Query q = entityManager.createNamedQuery("cx");//执行实体类注解中的jpql语句
        
        q.setParameter(1, 41);//添加jpql语句参数,占位符编号从1开始
        
        List<JPANews> l = q.getResultList();
        
        System.out.println("长度=" + l.size());
        
    }

}