Java：SpringBoot整合MyBatis-Plus实现MySQL数据库的增删改查

Posted 2023-02-09

MyBatis-Plus （简称 MP）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。

文档

• https://baomidou.com/

(目录)

一、引入坐标

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.5.2</version>
</dependency>

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <scope>runtime</scope>
</dependency>

其他版本 https://mvnrepository.com/artifact/com.baomidou/mybatis-plus-boot-starter

完整配置 pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<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>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.7.7</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <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>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>

        <!-- https://mvnrepository.com/artifact/com.baomidou/mybatis-plus-boot-starter -->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.5.2</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

二、配置

1、数据源配置

application.yml

# DataSource Config
spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/data?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=Asia/Shanghai
    username: root
    password: 123456

mybatis-plus:
  configuration:
    # 开启SQL语句打印
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  global-config:
    db-config:
      # 自增主键策略
      id-type: AUTO

2、分页配置

package com.example.demo.config;

import com.baomidou.mybatisplus.annotation.DbType;
import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/**
 * mp的分页拦截器
 */
@Configuration
public class MybatisPlusConfig 

    /**
     * 新版mp
     **/
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() 
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
        return interceptor;
    

3、创建数据表

在data数据库下创建表tb_user

CREATE TABLE `tb_user` (
  `id` int NOT NULL AUTO_INCREMENT COMMENT 主键id,
  `name` varchar(20) COMMENT 主键id,
  `age` int DEFAULT NULL COMMENT 姓名,
  PRIMARY KEY (`id`)
);

三、CURD测试

实体类

package com.example.demo.entity.domain;

import com.baomidou.mybatisplus.annotation.TableName;
import com.fasterxml.jackson.annotation.JsonProperty;
import lombok.Data;

/**
 * 数据库实体映射
 */
@Data
@TableName("tb_user")
public class User 
    private Long id;

    private String name;

    private Integer age;

Mapper

package com.example.demo.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.example.demo.entity.domain.User;
import org.apache.ibatis.annotations.Mapper;

@Mapper
public interface UserMapper extends BaseMapper<User> 

IService

package com.example.demo.service;

import com.baomidou.mybatisplus.extension.service.IService;
import com.example.demo.entity.domain.User;

public interface UserService extends IService<User> 

ServiceImpl

package com.example.demo.service.impl;

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

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

测试

package com.example.demo.service;

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.baomidou.mybatisplus.core.conditions.update.LambdaUpdateWrapper;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.example.demo.entity.domain.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.List;

@SpringBootTest
public class UserServiceTest 
    @Autowired
    private UserService userService;

    /**
     * 插入数据
     */
    @Test
    void testSave() 
        User user = new User();
        user.setName("Tom");
        user.setAge(20);

        userService.save(user);
        // INSERT INTO tb_user ( name, age ) VALUES ( ?, ? )
    

    /**
     * 字段更新
     */
    @Test
    void testUpdateById() 
        User user = new User();
        user.setId(1L);
        user.setAge(22);
        // 仅更新非空的属性
        userService.updateById(user);
        // UPDATE tb_user SET age=? WHERE id=?
    

    /**
     * 部分字段更新
     */
    @Test
    void testUpdateFieldById() 
        LambdaUpdateWrapper<User> updateWrapper = new LambdaUpdateWrapper<>();
        updateWrapper.eq(User::getId, 1);
        updateWrapper.set(User::getAge, 30);

        userService.update(updateWrapper);
        // UPDATE tb_user SET age=? WHERE (id = ?)
    

    /**
     * 查询单条数据
     */
    @Test
    void testGetById() 
        User user = userService.getById(1L);
        // SELECT id,name,age FROM tb_user WHERE id=?

        System.out.println(user);
        // User(id=1, name=Tom, age=22)
    

    /**
     * 查询多条数据
     */
    @Test
    void testSelect() 
        LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();
        queryWrapper.gt(User::getAge, 20);

        // 2次SQL，一次查总记录数，一次查具体数据
        // public Page(long current, long size, boolean searchCount)
        Page<User> page = new Page<>(1, 10);

        userService.page(page, queryWrapper);
        // SELECT COUNT(*) AS total FROM tb_user WHERE (age > ?)
        // SELECT id,name,age FROM tb_user WHERE (age > ?) LIMIT ?

        long total = page.getTotal();
        List<User> records = page.getRecords();

        System.out.println(total);
        // 1

        System.out.println(records);
        // [User(id=1, name=Tom, age=22)]
    

四、API数据接口

通过对象转换和字段转换，我们能很容易控制输入和输出

Controller

package com.example.demo.controller;
       
import com.example.demo.entity.domain.User;
import com.example.demo.entity.dto.UserDto;
import com.example.demo.entity.vo.UserVo;
import com.example.demo.service.UserService;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

@RestController
public class UserController 
   @Autowired
   private UserService userService;

   @PostMapping("/api/user/getUserById")
   public UserVo getUserById(@RequestBody UserDto userDto) 
       System.out.println(userDto);

       User user = userService.getById(userDto.getId());

       UserVo userVo = new UserVo();
       BeanUtils.copyProperties(user, userVo);

       return  userVo;
   

DTO

package com.example.demo.entity.dto;

import com.fasterxml.jackson.annotation.JsonProperty;
import lombok.Data;

/**
 * 接收前端提交的数据
 */
@Data
public class UserDto 
    @JsonProperty("user_id")
    private Long id;

VO

package com.example.demo.entity.vo;

import com.fasterxml.jackson.annotation.JsonProperty;
import lombok.Data;

/**
 * 返回前端的数据
 */
@Data
public class UserVo 
    @JsonProperty("user_id")
    private Long id;

    private String name;

    @JsonProperty("name_label")
    private String nameLabel;

    public String getNameLabel() 
        return "[" + name + ];
    

    private void setNameLabel() 
    

接口请求

POST http://localhost:8080/api/user/getUserById
Content-Type: application/json


  "user_id":  1

返回数据

  "name": "Tom",
  "user_id": 1,
  "name_label": "[Tom]"

完整代码: https://mouday.github.io/spring-boot-demo/