POJO

@Datapublic class User {    private Integer id;    private String name;    private Integer age;}

UserMapper

@Mapperpublic interface UserMapper {    List<User> selectAll();    int insert(User user);    int delete(Integer id);    int update(User user);}

UserMapper.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.zk.mapper.UserMapper">    <select id="selectAll" resultType="com.zk.pojo.User">        select * from user    </select>    <insert id="insert">        insert into user(id,name,age) values (#{id},#{name},#{age});    </insert>    <delete id="delete">        delete from user where id=#{id};    </delete>    <update id="update">        update user set id=#{id},name=#{name},age=#{age} where id=#{id};    </update></mapper>

UserService

public interface UserService {    List<User> selectAll();    int insert(User user);    int delete(Integer id);    int update(User user);}

UserServiceImpl

@Servicepublic class UserServiceImpl implements UserService {    @Autowired    private UserMapper userMapper;    @Override    public List<User> selectAll() {        return userMapper.selectAll();    }    @Override    public int insert(User user) {        return userMapper.insert(user);    }    @Override    public int delete(Integer id) {        return userMapper.delete(id);    }    @Override    public int update(User user) {        return userMapper.update(user);    }}

UserController

@RestControllerpublic class UserController {    @Autowired    private UserService userService;    @GetMapping(value = "select")    public List<User> selectAll(){        return userService.selectAll();    }    @PutMapping(value = "insert")    public String insert(@RequestBody User user){        userService.insert(user);        return "增加胜利";    }    @RequestMapping(value = "delete/{id}")    public String delete(@PathVariable Integer id){        userService.delete(id);        return "删除胜利";    }    @PostMapping(value = "update")    public String update(@RequestBody User user){        userService.update(user);        return "批改胜利";    }}