环境要求：

工具：IDEA
数据库版本：mysql5.7

一、环境搭建

1. 创建springboot项目

pom.xml

2. pom.xml : spring web、lombok mysql

  <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

3. 添加mybatisplus依赖

 		<dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.3.1.tmp</version>
        </dependency>

application.properties

4.application.properties配置文件：用户名、密码、连接驱动、配置日志

注意：mysql8 需要增加时区的配置 serverTimezone=GMT%2B8 东八区

#mysql5 驱动不同
spring.datasource.username=root
spring.datasource.password=123456
spring.datasource.url=jdbc:mysql://localhost:3306/mybatisplus?useSSL=false&useUnicode=true&characterEncoding=utf-8
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

#配置日志
mybatis-plus.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl

数据库数据

#建表
DROP TABLE IF EXISTS user;

CREATE TABLE user
(
	id BIGINT(20) NOT NULL COMMENT '主键ID',
	name VARCHAR(30) NULL DEFAULT NULL COMMENT '姓名',
	age INT(11) NULL DEFAULT NULL COMMENT '年龄',
	email VARCHAR(50) NULL DEFAULT NULL COMMENT '邮箱',
	PRIMARY KEY (id)
);

#插入数据
DELETE FROM user;

INSERT INTO user (id, name, age, email) VALUES
(1, 'Jone', 18, 'test1@baomidou.com'),
(2, 'Jack', 20, 'test2@baomidou.com'),
(3, 'Tom', 28, 'test3@baomidou.com'),
(4, 'Sandy', 21, 'test4@baomidou.com'),
(5, 'Billie', 24, 'test5@baomidou.com');

代码详解

1.新建实体类User
lombok注解详解：
@Data：自动生成get\set方法
@AllArgsConstructor ：有参方法
@NoArgsConstructor：无参方法
@TableId(value = “id”,type = IdType.AUTO) ：给实体设置自增

package com.sh.entity;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.springframework.context.annotation.Primary;

import java.util.Date;

@Data
@AllArgsConstructor
@NoArgsConstructor

public class User {
    @TableId(value = "id",type = IdType.AUTO)
    private Integer id;
    private String name;
    private Integer age;
    private String email;
    private Date createTime;
    private Date updateTime;
}

2. 新建mapper包
在mapper包里建UserMappe接口r 继承BaseMapper<实体类>

package com.sh.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.sh.entity.User;
import org.springframework.stereotype.Repository;

@Repository
public interface UserMapper extends BaseMapper<User> {

}

3.创建控制层controller：
新建UserController类

package com.sh.controller;

import com.sh.entity.User;
import com.sh.mapper.UserMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

@RestController
public class UserController {
    @Autowired
    private UserMapper userMapper;
    //查询 查询所以 null 就是没有条件
    @GetMapping("/selectUser")
    public List<User> getAll(){
        List<User> user = userMapper.selectList(null);
        return user;
    }
    //根据id查询
    @GetMapping("/selectById")
    public User selectUserById(){
        User user = userMapper.selectById(1);
        return user;
    }
    //根据多个id查询 Arrays.asList集合
    @GetMapping("/selectByIds")
    public List<User> selectUserByIds(){
        List<User> user = userMapper.selectBatchIds(Arrays.asList(1,2,3));
        return user;
    }
    //添加
    @PostMapping("/insertUser")
    public Integer insertUsers(User user){
        Integer result = userMapper.insert(user);
        return result;
    }
    //修改 根据id
    @PutMapping("/updateUser")
    public Integer updateUsers(User user){
       Integer result = userMapper.updateById(user);
        return result;
    }
    //删除 根据id
    @DeleteMapping("/deleteUser")
    public Integer deleteUsers(Integer id){
        Integer result = userMapper.deleteById(id);
        return result;
    }
}

项目结构

注意：添加，修改操作需要数据库和实体设置自增

具体详见:

MybatisPlus遇到坑之一
MybatisPlus遇到坑之二