在SpringData JPA 中实现对持久层的操作

1.导入依赖 hibernate 这个依赖自带实现JPA接口

<dependencies><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.12</version><scope>test</scope></dependency><dependency><groupId>org.hibernate</groupId><artifactId>hibernate-entitymanager</artifactId><version>5.4.32.Final</version></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.47</version></dependency></dependencies>

2.在resources目录下建立 META-INF文件夹 ，创建JPA   persistence.xml配置文件

 persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="2.0"><!--  需要配置persistence-unit 节点持久化单元:name: 持久化单元名称  可随时切换， 若是OpenJPA的实现方式就 换成 OpenJPA 就可以了transaction-type: 事务管理方式JTA:分布式事务管理RESOURCE_LOCAL:本地事务管理--><persistence-unit name="hibernateJPA" transaction-type="RESOURCE_LOCAL"><!--JPA 的 实现方式    顺序别搞错，要放在class上面    --><provider>org.hibernate.jpa.HibernatePersistenceProvider</provider><!--需要进行ORM 的POJO类 --><class>com.kuang.pojo.Customer</class><!-- 可选配置 :配置 JPA 实现方 的 配置信息       --><properties><!--   数据库信息用户名 , javax.persistence.jdbc.user密码  , javax.persistence.jdbc.password驱动  , javax.persistence.jdbc.driver数据库地址 , javax.persistence.jdbc.url--><property name="javax.persistence.jdbc.user" value="root"/><property name="javax.persistence.jdbc.password" value="2001"/><property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/><property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/springdata_jpa?useUnicode=true&amp;useSSL=false&amp;characterEncoding=UTF-8"/><!-- 配置JPA实现方 (hibernate) 的配置信息显示sql : false|true自动创建数据库表: hibernate.hbm2ddl.autocreate: 程序运行时创建数据库表（如果有表，先删除在创建）update: 程序运行时创建表（如果有表，不会创建表）none: 不会创建表--><property name="hibernate.show_sql" value="true"/><property name="hibernate.hbm2ddl.auto" value="update"/><property name="hibernate.dialect" value="org.hibernate.dialect.MySQL57InnoDBDialect"/></properties></persistence-unit></persistence>

3.创建测试类

package com.kuang.test;import com.kuang.pojo.Customer;
import org.junit.Before;
import org.junit.Test;import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;
import javax.xml.soap.SAAJMetaFactory;public class JpaTest {private EntityManagerFactory factory;@Beforepublic void before() {//EntityManagerFactory 创建工厂 对应 sqlSessionFactory  用来创建 entityManagerfactory = Persistence.createEntityManagerFactory("hibernateJPA");}@Testpublic void insert() {//其实底层实现还是hibernate// entityManager 相当于 sqlSession 代码与数据库之间的桥梁EntityManager entityManager = null;EntityTransaction transaction=null;try {entityManager = factory.createEntityManager();transaction = entityManager.getTransaction();//获取事务对象transaction.begin();//事务开启Customer customer = new Customer();customer.setCustName("刘备");customer.setCustAddress("锦州");entityManager.persist(customer);transaction.commit();//事务提交} catch (Exception e) {e.printStackTrace();transaction.rollback();//事务回滚} finally {if (entityManager!=null){entityManager.close();//关闭连接}}}@Testpublic void select() {//其实底层实现还是hibernate// entityManager 相当于 sqlSession 代码与数据库之间的桥梁EntityManager entityManager = null;EntityTransaction transaction=null;try {entityManager = factory.createEntityManager();transaction = entityManager.getTransaction();//获取事务对象transaction.begin();//事务开启Customer customer = entityManager.find(Customer.class, 1L);
//            Customer customer = entityManager.getReference(Customer.class, 1L);//延迟查询
//            System.out.println("=======");System.out.println(customer);transaction.commit();//事务提交} catch (Exception e) {e.printStackTrace();transaction.rollback();//事务回滚} finally {if (entityManager!=null){entityManager.close();//关闭连接}}}@Testpublic void update() {//其实底层实现还是hibernate// entityManager 相当于 sqlSession 代码与数据库之间的桥梁EntityManager entityManager = null;EntityTransaction transaction=null;try {entityManager = factory.createEntityManager();transaction = entityManager.getTransaction();//获取事务对象transaction.begin();//事务开启Customer customer = new Customer();customer.setCustId(9L);customer.setCustName("lzl");customer.setCustAddress("为鲁斯");/*** 如果指定了主键:*          更新 :1. 先查询 看是否有变化*         *如果有变化 更新  如果没有变化 就不更新* 如果没有指定主键:*         插入:*///存在即修改, 不存在就添加//注意： 修改是覆盖操作，你没给的值，就全给你覆盖为null// 如果你不想让他查一遍,你可以自己写JPQL语句进行添加或者修改Customer merge = entityManager.merge(customer);transaction.commit();//事务提交} catch (Exception e) {e.printStackTrace();transaction.rollback();//事务回滚} finally {if (entityManager!=null){entityManager.close();//关闭连接}}}@Testpublic void update_JPQL() {//其实底层实现还是hibernate// entityManager 相当于 sqlSession 代码与数据库之间的桥梁EntityManager entityManager = null;EntityTransaction transaction=null;try {entityManager = factory.createEntityManager();transaction = entityManager.getTransaction();//获取事务对象transaction.begin();//事务开启String jpql="update Customer set custName=:custName , custAddress=:custAddress where custId=:id";entityManager.createQuery(jpql).setParameter("custName","张杰").setParameter("custAddress","广东").setParameter("id",3L).executeUpdate();transaction.commit();//事务提交} catch (Exception e) {e.printStackTrace();transaction.rollback();//事务回滚} finally {if (entityManager!=null){entityManager.close();//关闭连接}}}@Testpublic void test_SQL() {//其实底层实现还是hibernate// entityManager 相当于 sqlSession 代码与数据库之间的桥梁EntityManager entityManager = null;EntityTransaction transaction=null;try {entityManager = factory.createEntityManager();transaction = entityManager.getTransaction();//获取事务对象transaction.begin();//事务开启String sql="update tb_customer set cust_name=:custName , cust_address=:custAddress where  cust_id=:id";entityManager.createNativeQuery(sql).setParameter("custName","谢娜").setParameter("custAddress","湖南").setParameter("id",3L).executeUpdate();transaction.commit();//事务提交} catch (Exception e) {e.printStackTrace();transaction.rollback();//事务回滚} finally {if (entityManager!=null){entityManager.close();//关闭连接}}}@Testpublic void delete() {//其实底层实现还是hibernate// entityManager 相当于 sqlSession 代码与数据库之间的桥梁EntityManager entityManager = null;EntityTransaction transaction=null;try {entityManager = factory.createEntityManager();transaction = entityManager.getTransaction();//获取事务对象transaction.begin();//事务开启Customer customer = entityManager.find(Customer.class, 3L);entityManager.remove(customer);// 这样删除，是删除游离状态的，会抛异常不允许这样操作  IllegalArgumentException: Removing a detached instance com.kuang.pojo.Customer#3transaction.commit();//事务提交} catch (Exception e) {e.printStackTrace();transaction.rollback();//事务回滚} finally {if (entityManager!=null){entityManager.close();//关闭连接}}}@Testpublic void template() {//其实底层实现还是hibernate// entityManager 相当于 sqlSession 代码与数据库之间的桥梁EntityManager entityManager = null;EntityTransaction transaction=null;try {entityManager = factory.createEntityManager();transaction = entityManager.getTransaction();//获取事务对象transaction.begin();//事务开启transaction.commit();//事务提交} catch (Exception e) {e.printStackTrace();transaction.rollback();//事务回滚} finally {if (entityManager!=null){entityManager.close();//关闭连接}}}
}