springboot jpa 操作mysql

1. 创建springboot项目

2. 编写application.yml配置文件

server:
  port: 8080
  servlet:
    context-path: /

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/test?serverTimezone=UTC
    username: root
    password: root
    # type: com.alibaba.druid.pool.DruidDataSource  # 链接池 druid

  jpa:
    database: mysql
    show-sql: true # 显示sql
    hibernate:
      ddl-auto: update # jpa的正向工程

3. 编写实体类

• pojo.User.java

package com.adley.studyspringdatajpa.pojo;

import javax.persistence.*;


@Entity
@Table(name="t_users")
public class User {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Integer id;

    @Column(name = "name")
    private String name;

    @Column(name = "age")
    private Integer age;

    @Column(name = "address")
    private String address;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                ", address='" + address + '\'' +
                '}';
    }
}

4. 编写dao接口

• dao.UserRepository.java

package com.adley.studyspringdatajpa.dao;

import com.adley.studyspringdatajpa.pojo.User;
import org.springframework.data.jpa.repository.JpaRepository;

public interface UserRepository extends JpaRepository<User, Integer> {
}

5. 编写service业务逻辑层

• service.UserService.java

package com.adley.studyspringdatajpa.service;

import com.adley.studyspringdatajpa.dao.UserRepository;
import com.adley.studyspringdatajpa.pojo.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.PageRequest;
import org.springframework.stereotype.Service;

import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;

@Service
public class UserService {

    @Autowired
    private UserRepository userRepository;

    /**
     * 保存一条用户信息
     */
    public User saveUser(User user) {
        return userRepository.save(user);
    }

    /**
     * 根据id删除一个用户信息
     */
    public void deleteUser(Integer id) {
        userRepository.deleteById(id);
    }

    /**
     * 更新用户
     */
    public User updateUser(User user) {
        return userRepository.saveAndFlush(user);
    }

    /**
     * 查询一条用户信息
     */
    public User findUserById(Integer id) {
        Optional<User> optional = userRepository.findById(id);
        return optional.orElseGet(User::new);
    }

    /**
     * 查询多条用户list 分页
     */
    public Map<String, Object> findUserAll(Integer pageNum, Integer pageSize) {
        List<User> content = userRepository.findAll(PageRequest.of(pageNum - 1, pageSize)).getContent();
        HashMap<String, Object> map = new HashMap<>();
        map.put("pageNum", pageNum);
        map.put("pageSize", pageSize);
        map.put("content", content);
        return map;
    }

}

6. 编写单元测试TestMysql.java

package com.adley.studyspringdatajpa;

import com.adley.studyspringdatajpa.pojo.User;
import com.adley.studyspringdatajpa.service.UserService;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.Map;

@SpringBootTest
public class TestMysql {

    @Autowired
    private UserService userService;

    /**
     * 添加一个用户
     */
    @Test
    void testSaveUser() {
        User user = new User();
        user.setName("王东东");
        user.setAge(21);
        user.setAddress("北京");

        /**
         * 返回保存的user信息
         */
        User save_user = userService.saveUser(user);
        System.out.println(save_user);
    }

    /**
     * 查找一个用户
     */
    @Test
    void testFindUser() {
        Integer id = 2;
        User user = userService.findUserById(id);
        System.out.println(user);
    }

    /**
     * 更新用户，只是更新部分字段
     */
    @Test
    void testUpdateUser() {
        Integer id = 3;
        User user = userService.findUserById(id);

        user.setAge(28);
        user.setName("王小龙");

        User user1 = userService.updateUser(user);
        System.out.println(user1);
    }

    /**
     * 查询用户列表
     */
    @Test
    void testFindUsers() {
        Map<String, Object> data = userService.findUserAll(1, 15);
        System.out.println(data);
    }

    /**
     * 删除一个用户
     */
    @Test
    void testDelteUserById() {
        Integer id = 2;
        userService.deleteUser(id);
    }
}