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());

     }

 }