SpringBoot系列之集成MybatisPlus操作指南

Posted 2022-01-29 smileNicky

1、什么是mybatisPlus？

MyBatis-Plus ，引用官网的说法：

MyBatis-Plus (opens new window)（简称 MP）是一个 MyBatis (opens new window)的增强工具，在 MyBatis 的基础上只做增强不做改变，为简化开发、提高效率而生。

2、创建MybatisPlus项目

开发环境

• JDK 1.8
• SpringBoot2.2.1
• Maven 3.2+
• mysql5.7.36
• 开发工具
  • IntelliJ IDEA
  • smartGit

使用阿里的脚手架，链接：https://start.aliyun.com

选择mybatis plus framework

新建application.yml，加上配置：

mybatis-plus:
  type-aliases-package: com.example.mybatisplus.*.*.model
  mapper-locations: classpath*:mapper/*/*.xml
  configuration:
    map-underscore-to-camel-case: true
    default-statement-timeout: 60

创建数据库表，sql使用官网的

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)
);

表数据，数据使用官网的

DELETE FROM user;

INSERT INTO user (id, name, age, email) VALUES
(1, 'Jone', 18, '[e-mail]'),
(2, 'Jack', 20, '[e-mail]'),
(3, 'Tom', 28, '[e-mail]'),
(4, 'Sandy', 21, '[e-mail]'),
(5, 'Billie', 24, '[e-mail]');

3、MybatisPlus快速入门

写一个例子，写一套RestFul风格的curd接口：

加上注解@TableName，id加上@TableId

package com.example.mybatisplus.model;

import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;
import lombok.experimental.SuperBuilder;

import java.io.Serializable;

@TableName("user")
@Data
@SuperBuilder(toBuilder = true)
@AllArgsConstructor
@NoArgsConstructor
@ToString
public class User implements Serializable 
    @TableId
    private Long id;
    private String name;
    private Integer age;
    private String email;

加上一个mapper类，继承BaseMapper

package com.example.mybatisplus.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.example.mybatisplus.model.User;

public interface UserMapper extends BaseMapper<User>

MapperScan扫描具体的mapper包，就不需要每个mapper类都加@Mapper

package com.example.mybatisplus;

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

@SpringBootApplication
@MapperScan("com.example.mybatisplus.mapper")
public class SpringbootMybatisPlusApplication 

    public static void main(String[] args) 
        SpringApplication.run(SpringbootMybatisPlusApplication.class, args);
    

接口实现IService

package com.example.mybatisplus.service;
import com.baomidou.mybatisplus.extension.service.IService;
import com.example.mybatisplus.model.User;
public interface IUserService extends IService<User> 

接口实现类实现ServiceImpl

package com.example.mybatisplus.service.impl;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.example.mybatisplus.mapper.UserMapper;
import com.example.mybatisplus.model.User;
import com.example.mybatisplus.service.IUserService;
import org.springframework.stereotype.Service;
@Service
public class UserServiceImpl extends ServiceImpl<UserMapper , User> implements IUserService 

写一个RestFul风格的控制类：

package com.example.mybatisplus.controller;

import cn.hutool.core.bean.BeanUtil;
import com.example.mybatisplus.common.ResultBean;
import com.example.mybatisplus.model.User;
import com.example.mybatisplus.model.dto.UserDto;
import com.example.mybatisplus.model.vo.UserVo;
import com.example.mybatisplus.service.impl.UserServiceImpl;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping(value = "/api")
public class UserController 

    @Autowired
    private UserServiceImpl userService;

    @GetMapping(value = "/user")
    public ResultBean<List<UserVo>> users() 
        List<User> poList = userService.list();
        List<UserVo> voList = BeanUtil.copyToList(poList , UserVo.class);
        return ResultBean.ok(voList);
    

    @GetMapping(value = "/user/id")
    public ResultBean<UserVo> user(@PathVariable("id")Integer id) 
        User user = userService.getById(id);
        UserVo userVo = BeanUtil.copyProperties(user , UserVo.class);
        return ResultBean.ok(userVo);
    

    @PostMapping(value = "/user")
    public ResultBean<User> save(@RequestBody UserDto userDto) 
        User user = BeanUtil.copyProperties(userDto , User.class);
        boolean flag = userService.save(user);
        if (flag) return ResultBean.ok(user);
        return ResultBean.badRequest("新增失败");
    

    @DeleteMapping(value = "/user/id")
    public ResultBean<Integer> del(@PathVariable("id") Integer id) 
        boolean flag = userService.removeById(id);
        if (flag) return ResultBean.ok(id);
        return ResultBean.badRequest("删除失败");
    

    @PutMapping(value = "/user")
    public ResultBean<User> update(@RequestBody UserDto userDto) 
        User user = BeanUtil.copyProperties(userDto , User.class);
        boolean flag = userService.updateById(user);
        if (flag) return ResultBean.ok(user);
        return ResultBean.badRequest("更新失败");
    

封装一个ResultBean类：

package com.example.mybatisplus.common;

import lombok.Data;
import org.springframework.http.HttpStatus;

/**
 * <pre>
 *      ResultBean
 * </pre>
 *
 * <pre>
 * @author mazq
 * 修改记录
 *    修改后版本:     修改人：  修改日期: 2020/08/10 17:07  修改内容:
 * </pre>
 */
@Data
public class ResultBean<T> 

	/**
	 * 状态
	 * */
	private int status;
	/**
	 * 描述
	 * */
	private String desc;
	/**
	 * 数据返回
	 * */
	private T data;

	public ResultBean(int status, String desc, T data) 
		this.status = status;
		this.desc = desc;
		this.data = data;
	

	public ResultBean(T data) 
		this.status = HttpStatus.OK.value();
		this.desc = "处理成功";
		this.data = data;
	

	public static <T> ResultBean<T> ok(T data) 
		return new ResultBean(data);
	

	public static <T> ResultBean<T> ok() 
		return new ResultBean(null);
	

	public static <T> ResultBean<T> badRequest(String desc,T data) 
		return new ResultBean(HttpStatus.BAD_REQUEST.value(), desc, data);
	

	public static <T> ResultBean<T> badRequest(String desc) 
		return new ResultBean(HttpStatus.BAD_REQUEST.value(), desc, null);
	

	public static <T> ResultBean serverError(String desc, T data)
		return new ResultBean(HttpStatus.INTERNAL_SERVER_ERROR.value(),"服务器内部异常:"+desc,data);
	

	public static <T> ResultBean serverError(String desc)
		return new ResultBean(HttpStatus.INTERNAL_SERVER_ERROR.value(),"服务器内部异常:"+desc,null);
	

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>dynamic-datasource-spring-boot-starter</artifactId>
    <version>3.4.1</version>
</dependency>

4、多数据源配置

pom加上配置：

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter-test</artifactId>
    <version>3.4.3.4</version>
</dependency>

多数据源，参考官网

spring:
  datasource:
    dynamic:
      primary: shop #设置默认的数据源或者数据源组,默认值即为master
      strict: false #严格匹配数据源,默认false. true未匹配到指定数据源时抛异常,false使用默认数据源
      datasource:
        shop:
          url: jdbc:mysql://127.0.0.1:3306/shop?useUnicode=true&characterEncoding=utf-8
          username: root
          password:
          driver-class-name: com.mysql.jdbc.Driver # 3.2.0开始支持SPI可省略此配置
          schema: classpath:db/schema-mysql.sql
          data: classpath:db/data-mysql.sql
        slave_1:
          url: jdbc:mysql://127.0.0.1:3306/canaltest?useUnicode=true&characterEncoding=utf-8
          username: root
          password:
          driver-class-name: com.mysql.jdbc.Driver

表格来自官网：

package com.example.mybatisplus.mapper;

import com.baomidou.dynamic.datasource.annotation.DS;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.example.mybatisplus.model.User;

@DS(value = "shop")
public interface UserMapper extends BaseMapper<User>

有些版本可能可能会出现异常：Failed to configure a DataSource: ‘url‘ attribute is not specified and no embedded datasource

这种情况，可以排查数据源的自动配置

@SpringBootApplication(exclude= DataSourceAutoConfiguration.class)

5、MybatisPlus测试

pom配置：

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter-test</artifactId>
    <version>3.4.3.4</version>
</dependency>

测试类：

package com.example.mybatisplus;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.test.autoconfigure.MybatisPlusTest;
import com.example.mybatisplus.mapper.UserMapper;
import com.example.mybatisplus.model.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;

import java.util.List;

@MybatisPlusTest
class MybatisPlusSampleTest 

    @Autowired
    private UserMapper userMapper;

    @Test
    void test() 
        List<User> userList = userMapper.selectList(new QueryWrapper<User>());
        userList.stream().forEach(System.out::println);
    

6、和Lambda表达式的妙用

mybatisPlus支持Lambda表示式，单表查询的业务一遍用不上，还是给下具体的业务场景：列举电商spu和sku的例子，spu表和sku表有一张关联表，传入一个spuCode，查询对应的spu清单，具体sql

SELECT
	* 
FROM
	t_sku sku
	LEFT JOIN t_spu_sku_relate r ON sku.skuCode = r.skuCode 
WHERE
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