增删改查代码编写

UserController.java

package com.zj.demo.controller;

import com.zj.demo.entity.User;
import com.zj.demo.mapper.UserMapper;
import com.zj.demo.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/user")
public class UserController {


    @Autowired
    private UserMapper userMapper;

    @Autowired
    private UserService userService;

    // 新增和修改
    @PostMapping
    public Integer save(@RequestBody User user) {
        // 新增或者更新
        return userService.save(user);
    }

    // 查询所有数据
    @GetMapping
    public List<User> index() {
        List<User> all = userMapper.findAll();
        return all;
    }

    @DeleteMapping("/{id}")
    public Integer delete(@PathVariable Integer id) {
        return userMapper.deleteById(id);
    }
}

UserMapper.java

package com.zj.demo.mapper;

import com.zj.demo.entity.User;
import org.apache.ibatis.annotations.*;

import java.util.List;

@Mapper
public interface UserMapper {

    @Select("SELECT * from sys_user")
    List<User> findAll();

    @Insert("INSERT into sys_user(username, password,nickname,email,phone,address) VALUES (#{username}, #{password}," +
            " #{nickname}, #{email},#{phone}, #{address})")
    int insert(User user);

   
    int update(User user);

    @Delete("delete from sys_user where id = #{id}")
    Integer deleteById(@Param("id") Integer id);

}

UserService.java

package com.zj.demo.service;

import com.zj.demo.entity.User;
import com.zj.demo.mapper.UserMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class UserService {

    @Autowired
    private UserMapper userMapper;

    public int save(User user) {
        // user没有id，则表示是新增
        // 否则为更新
        if (user.getId() == null) {
            return userMapper.insert(user);
        } else {
            return userMapper.update(user);
        }
    }

}

postman测试后台接口

下载地址：
https://app.getpostman.com/app/download/win64

postman测试接口
在这里插入图片描述

动态SQL编写：

1、update如果写成下面这个方式，用户提交的每个请求都会反映到数据库，不太好
如果有字段不需要更新就很麻烦
在这里插入图片描述

所以需要用动态SQL【相关代码见下】
记得IDEA安装MybatisX插件

User.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.qingge.springboot.mapper.UserMapper">

    <update id="update">
        update sys_user
        <set>
            <if test="username != null">
                username = #{username},
            </if>
<!--            <if test="password != null">-->
<!--                password = #{password}-->
<!--            </if>-->
            <if test="nickname != null">
                nickname = #{nickname},
            </if>
            <if test="email != null">
                email = #{email},
            </if>
            <if test="phone != null">
                phone = #{phone},
            </if>
            <if test="address != null">
                address = #{address}
            </if>
        </set>
        <where>
            id = #{id}
        </where>
    </update>

</mapper>

application.yml

server:
  port: 9090

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/qing?serverTimezone=GMT%2b8
    username: root
    password: 123456
mybatis:
  mapper-locations: classpath:mapper/*.xml  #扫描所有mybatis的xml文件
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl