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

        
            junit
            junit
            4.12
            test
        

        
            org.hibernate
            hibernate-entitymanager
            5.4.32.Final
        
        
            mysql
            mysql-connector-java
            5.1.47
        
    

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

 persistence.xml

   
    

        
        org.hibernate.jpa.HibernatePersistenceProvider
        
        com.kuang.pojo.Customer


        

        
            
            
            
            
            

            
            
            
            

        
    

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;

    @Before
    public void before() {
        //EntityManagerFactory 创建工厂 对应 sqlSessionFactory  用来创建 entityManager
        factory = Persistence.createEntityManagerFactory("hibernateJPA");
    }

    @Test
    public 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
            }
        }

    }

    @Test
    public 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
            }
        }

    }
    @Test
    public 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
            }
        }

    }


    @Test
    public 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
            }
        }

    }
    @Test
    public 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
            }
        }

    }

    @Test
    public 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#3

            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
            }
        }

    }

    @Test
    public 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
            }
        }

    }
}