使用springdatajpa框架實現增刪改查

在實現增刪該查之前准備工作  和入門一樣

在測試類中：

package cn.yqk.jpa;

import cn.yqk.pojo.Customer;
import org.junit.Before;
import org.junit.Test;

import javax.persistence.*;
import java.util.List;

/**
 * @author Yang
 * @date 2019/8/15 13:58
 */
public class JpaManager {
    private EntityManagerFactory entityManagerFactory;
    private EntityManager entityManager;
    EntityTransaction transaction;
    @Before  //表示在優先執行
    public void init(){//初始化方法
          //創建EntityManagerFactory工廠
        entityManagerFactory =     
        Persistence.createEntityManagerFactory("myjpa"); 
        //根據factory工廠對象獲Entity對象
        entityManager = entityManagerFactory.createEntityManager();
        transaction = entityManager.getTransaction();      
    }
 //添加
    @Test
    public void addCustomer() {
        //開啟事務
        transaction.begin();
        for (int i = 0; i < 20; i++) {
            Customer customer = new Customer();
            customer.setCstName("張" + i);
            customer.setCstAddress("豫" + i);
            customer.setCstIndustry("測試");
            customer.setCstLevel("VIP" + i);
            customer.setCstSource("00" + i);
            entityManager.persist(customer);
        }
        //提交事務
        transaction.commit();
        //關閉釋放資源
        entityManager.close();
        entityManagerFactory.close();

    }
//刪除數據
    @Test
    public void delCustomer() {
        //開啟事務
        transaction.begin();
        //刪除數據之前要先查詢數據
        //查詢數據
        Customer customer = entityManager.find(Customer.class, 20l);
        //刪除該數據
        entityManager.remove(customer);
        //提交事務
        transaction.commit();
        //關閉
        entityManager.close();
        entityManagerFactory.close();
    }

    //修改數據
    @Test
    public void update() {
        //開啟事務
        transaction.begin();
        //修改數據之前也熬先查詢一條customer信息
        Customer customer = entityManager.find(Customer.class, 19l);
        customer.setPhone("1111111");
        customer.setCstSource("測試");
        customer.setCstIndustry("aaa");
        customer.setCstAddress("asd");
        customer.setCstName("張憨憨");
        //修改方法merge
        entityManager.merge(customer);
        //提交事務
        transaction.commit();
        //關閉連接
        entityManager.close();
        entityManagerFactory.close();
    }

    //根據id查詢（find方法）  即時加載
    @Test
    public void findById() {
        Customer customer = entityManager.find(Customer.class, 19l);
        System.out.println("============================");
        //打印結果
        System.out.println(customer);
        //關閉連接
        entityManager.close();
        entityManagerFactory.close();
    }

    //根據id查詢(getReference)  延時加載  當訪問對象時加載
    @Test
    public void findById0() {
        Customer reference = entityManager.getReference(Customer.class, 18l);
        System.out.println(reference);
        entityManager.close();
        entityManagerFactory.close();
    }

    //JPQL查詢  相當於sql語句中的一個變種
    //查詢全部
    @Test
    public void findAll() {
        //使用EntityManager創建Query對象
        Query query = entityManager.createQuery("from Customer");
        //使用query對象執行查詢
        List<Customer> resultList = query.getResultList();
        for (Customer customer : resultList) {
            System.out.println(customer);
        }
        entityManager.close();
        entityManagerFactory.close();
    }

    //分頁查詢
    @Test
    public void findByPage() {
        //創建query對象
        Query query = entityManager.createQuery("from Customer");
        //設置分頁信息
//        query.setFirstResult(0);//表示從第幾個開始
//        query.setMaxResults(5);//表示每頁顯示的數據
//        List<Customer> resultList = query.getResultList();
//        for(Customer customer:resultList){
//            System.out.println(customer);
//        }
        for (int i = 0; i < 20; i += 5) {
            System.out.println(i == 0);
            query.setFirstResult(i);
            query.setMaxResults(5);
            List<Customer> resultList = query.getResultList();
            for (Customer customer : resultList) {
                System.out.println(customer);
            }
            System.out.println("=======================");
        }
        entityManager.close();
    }

    //帶條件查詢
    //根據id查詢
    @Test
    public void findById2() {
        Query query = entityManager.createQuery("from Customer where cstId=?1");
        //設置條件
        //表示給編號為1的參數設值  編號可以為0或任意正整數但必須與？后面的值保持一致 並且？與后面的數值中間不能用空格
        query.setParameter(1, 9l);
        Customer customer = (Customer) query.getSingleResult();
        System.out.println(customer);
        entityManager.close();
    }

    //模糊查詢
    @Test
    public void findM() {
        Query query = entityManager.createQuery("from Customer where cstName like ?1 and cstAddress like ?2");
        //設置參數
        query.setParameter(1, "%張%");
        query.setParameter(2, "%豫%");
        List<Customer> resultList = query.getResultList();
        for (Customer customer : resultList) {
            System.out.println(customer);
        }
        entityManager.close();
    }
    //排序
    @Test
    public void findAllByOrder(){
        //desc 倒序
        Query query = entityManager.createQuery("from Customer order by cstId desc");
        List<Customer> resultList = query.getResultList();
        for (Customer customer:resultList){
            System.out.println(customer);
        }
        entityManager.close();
    }
    //聚合函數
    @Test
    public void findAllCount(){
//        Query query = entityManager.createQuery("select count(*) from Customer");
        Query query = entityManager.createQuery("select sum(cstId) from Customer");
        Object count = query.getSingleResult();
        System.out.println(count);
        entityManager.close();
    }
}

總結：

　　1.入門程序　　引入依賴     編寫配置文件　編寫實體類　  測試代碼

　　2.測試方法     

　　　　添加     persist　　刪除     remove (需要注意的是使用remove時要先查詢)　　修改   merge 　　查詢  find(即時加載)  getReference(延時加載   在訪問對象時加載)

　　3.JPQL

　　　　把sql語句中的表明變為實體類類名

　　　　字段名改為實體類屬性名