【SpringBoot深入浅出系列】SpringBoot之集成MyBatis-Plus

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一、MyBatis-Plus 是什么？

MyBatis-Plus （简称 MP）是国人团队苞米豆在 Mybatis 的基础上开发的框架，已连续 5 年（2017、2018、2019、2020、2021获得“OSC 年度最受欢迎中国开源软件”殊荣。是一个 MyBatis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。

二、创建项目集成 MyBatis-Plus

1.项目说明

新建 Spring Initializr 项目 mybatis，项目下新建controller、entity、mapper、service类。创建 MySQL 数据库 shop，shop 下创建 user 表。项目实现读取 user 表的信息。
项目目录结构：

2.创建 Spring Initializr 项目 mybatisplus

（1）.添加依赖

添加依赖，如果已按截图操作，pom.xml 还需引入 mybatis-plus-boot-starter 依赖：

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0modelVersion>
    <parent>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-parentartifactId>
        <version>2.6.3version>
        <relativePath/> 
    parent>
    <groupId>com.chaoyuegroupId>
    <artifactId>mybatisplusartifactId>
    <version>0.0.1-SNAPSHOTversion>
    <name>mybatisplusname>
    <description>Demo project for Spring Bootdescription>
    <properties>
        <java.version>1.8java.version>
    properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-jdbcartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-webartifactId>
        dependency>
        <dependency>
            <groupId>com.baomidougroupId>
            <artifactId>mybatis-plus-boot-starterartifactId>
            <version>3.4.3.4version>
        dependency>

        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <scope>runtimescope>
        dependency>
        <dependency>
            <groupId>org.projectlombokgroupId>
            <artifactId>lombokartifactId>
            <optional>trueoptional>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-testartifactId>
            <scope>testscope>
        dependency>
    dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.bootgroupId>
                <artifactId>spring-boot-maven-pluginartifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombokgroupId>
                            <artifactId>lombokartifactId>
                        exclude>
                    excludes>
                configuration>
            plugin>
        plugins>
    build>

project>

（2）.添加配置

application.yml 文件中添加如下配置：

server:
  port: 8080
spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/shop?characterEncoding=utf-8&useSSL=false
    username: root
    password: 123456

（3）.新建实体类 User

为减少不必要的代码，引入 lombok 依赖。实体类代码如下：

package com.chaoyue.mybatisplus.entity;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import lombok.Data;

@Data
public class User {
    @TableId(type = IdType.AUTO)
    private Long id; // id
    private String username; // 用户名
    private String password; // 密码
}

（4）.新建 Mapper 接口类 UserMapper

package com.chaoyue.mybatisplus.mapper;

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

@Repository
public interface UserMapper extends BaseMapper<User> {
}

（5）.新建服务接口类 UserService

package com.chaoyue.mybatisplus.service;

import com.baomidou.mybatisplus.extension.service.IService;
import com.chaoyue.mybatisplus.entity.User;

public interface UserService extends IService<User> {
}

（6）.新建服务实现类 UserServiceImpl

package com.chaoyue.mybatisplus.service.impl;

import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.chaoyue.mybatisplus.entity.User;
import com.chaoyue.mybatisplus.mapper.UserMapper;
import com.chaoyue.mybatisplus.service.UserService;
import org.springframework.stereotype.Service;

@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User>implements UserService {
}

（7）.新建控制类 UserController

package com.chaoyue.mybatisplus.controller;

import com.chaoyue.mybatisplus.entity.User;
import com.chaoyue.mybatisplus.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;
import java.util.List;

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

    @Autowired
    private UserService userService;

    @RequestMapping("/getAll")
    public String getAll() {
        List<User> list = userService.list();
        return list.toString();
    }

    @RequestMapping("/insert")
    public String insert() {
        User user = new User();
        user.setUsername("mybatisplus");
        user.setPassword("123456");
        userService.save(user);
        return getAll();
    }
}

（8）.启动类添加注解

启动类添加注解 @MapperScan(“com.chaoyue.mybatisplus.mapper”)

package com.chaoyue.mybatisplus;

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

@SpringBootApplication
@MapperScan("com.chaoyue.mybatisplus.mapper")
public class MybatisplusApplication {

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

}

3.创建数据库 shop 和数据表 user

-- ----------------------------
-- Table structure for user
-- ----------------------------
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user`  (
  `id` int(11) NOT NULL AUTO_INCREMENT COMMENT 'id',
  `username` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL COMMENT '用户名',
  `password` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL COMMENT '密码',
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 3 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci COMMENT = '用户表' ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of user
-- ----------------------------
INSERT INTO `user` VALUES (1, 'admin', 'admin');
INSERT INTO `user` VALUES (2, 'test', '123456');

SET FOREIGN_KEY_CHECKS = 1;

4.启动服务并测试

启动服务后，浏览器输入：http://localhost:8080/user/getAll，返回：

浏览器输入：http://localhost:8080/user/insert，返回：

PS：MyBatis-Plus 官网链接：https://baomidou.com/