创建表

create table user(
	id int ,
	name varchar(30),
	pwd varchar(40)
)

insert into `user` values(2,'hxf','789101'),(3,'hlm','789102'),(4,'hzh','789103'),(1,'hy','789110')

现在的表内容：
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目标的内容：

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创建项目

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我的POM文件依赖

<dependencies>
        <!--mysql-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.18</version>
        </dependency>
        <!--druid连接池--><dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>druid</artifactId>
        <version>1.1.22</version>
    </dependency>
        <!--mybatis-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.1.4</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.6</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.16.18</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

yml文件

server:
        port: 8080
spring:
        datasource:
                username: root
                password: 5****6
                url: jdbc:mysql://localhost:3306/test?serverTimezone=UTC&useUnicode=true&characterEncoding=utf8
                driver-class-name: com.mysql.cj.jdbc.Driver
                type: com.alibaba.druid.pool.DruidDataSource
mybatis:
        #  mapper文件
        mapper-locations: dao/*Dao.xml

实体类

package com.example.demo.vo;

import lombok.AllArgsConstructor;
import lombok.Data;

@Data
@AllArgsConstructor
public class User {
    private int id;
    private String name;
    private String pwd;
}

DAO接口

package com.example.demo.dao;
import com.example.demo.vo.User;
import java.util.List;
public interface UserDao {

    public List<User> selectUser();

    int insertUser(User user);

    int deleteUser(String name);

    int updateUser(String name);
}

写sql的XML文件

<?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.example.demo.dao.UserDao">
    <insert id="insertUser" parameterType="com.example.demo.vo.User">
        insert into user values(#{id},#{name},#{pwd})
    </insert>
    <update id="updateUser" parameterType="string">
        update `user` set pwd = '789100' where NAME = 'hy'
    </update>

    <delete id="deleteUser" parameterType="string">
        delete from user where name = #{name}
    </delete>

    <select id="selectUser" resultType="com.example.demo.vo.User">
        SELECT * FROM user order by pwd
    </select>
</mapper>

Service层

package com.example.demo.service;
import com.example.demo.dao.UserDao;
import com.example.demo.vo.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class UserService {
    @Autowired
    private UserDao userDao;

    public List<User> selectUser() {
        return userDao.selectUser();
    }

    public void addUser(User user){
        userDao.insertUser(user);
    }


    public void deleteUser(String name){
        userDao.deleteUser(name);
    }

    public void updateUser(String name){
        userDao.updateUser(name);
    }
}

Controller

package com.example.demo.controller;

import com.example.demo.service.UserService;
import com.example.demo.vo.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.Iterator;
import java.util.List;

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

    @Autowired(required = false)
    private UserService userService;

    @GetMapping("/query")
    public  String query(){
        String result="";
        List<User> userList = userService.selectUser();

        Iterator<User> iterator = userList.iterator();
        while(iterator.hasNext()){
            User next = iterator.next();
            result += next.toString();
        }
        return result;


//        for (User user : usersList) {
//            result +=user.toString();
//        }
//        return result;
    }


    @GetMapping("/add")
    public String addUser(){
        userService.addUser(new User(5,"hss","789104"));
        return "add ok";
    }

    @GetMapping("/delete")
    public String deleteUser(){
        userService.deleteUser("hzb");
        return "delete ok";
    }

    @GetMapping("/update")
    public String updateUser(){
        userService.updateUser("hy");
        return "update ok";
    }
}

启动类

package com.example.demo;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@MapperScan("com.example.demo.dao")
public class DemoApplication {
	public static void main(String[] args) {
		SpringApplication.run(DemoApplication.class, args);
	}
}

结果

用postman查询：localhost:8080/test/query
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添加：localhost:8080/test/add

删除:localhost:8080/test/delete

修改:localhost:8080/test/update

最终结果：localhost:8080/test/query