SpringBoot集成Mybatis-Plus增删改查

一、前言

Mybatis：数据持久化框架
Mybatis-Plus：对Mybatis进行了增强，它封装了基本的增删改查操作，使我们自己不需要再去写很多重复的代码，大大解放了生产力！

二、创建项目

创建成功后删除src下面的test目录

三、目录结构

四、pom.xml

修改pom.xml内容如下

<?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">
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.2.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <modelVersion>4.0.0</modelVersion>
    <groupId>com.llh</groupId>
    <artifactId>spring-boot-demo</artifactId>
    <version>1.0.0</version>
    <name>spring-boot-demo</name>
    <description>springboot project description</description>

    <properties>
        <mybatis-spring-boot.version>2.1.4</mybatis-spring-boot.version>
        <mybatis-plus.version>3.4.2</mybatis-plus.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

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

        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>${mybatis-spring-boot.version}</version>
        </dependency>

        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>${mybatis-plus.version}</version>
        </dependency>

    </dependencies>

</project>

说明：
中 spring-boot-starter-parent 帮我们做了SpringBoot相关依赖包的版本号管理，所以有些依赖包不需要我们自己去写
但像 mybatis-plus-boot-starter 它是不属于spring-boot相关的， parent中没有做版本号管理，所以还需要手动写一下。

五、sql和application.properties

5.1 导入sql语句

CREATE TABLE `user_info` (
	`id` BIGINT(20) NOT NULL AUTO_INCREMENT COMMENT '用户id',
	`username` VARCHAR(20) NOT NULL DEFAULT '' COMMENT '用户名' COLLATE 'utf8mb4_general_ci',
	`password` VARCHAR(100) NOT NULL DEFAULT '' COMMENT '密码' COLLATE 'utf8mb4_general_ci',
	`create_time` DATETIME NOT NULL COMMENT '创建时间',
	PRIMARY KEY (`id`) USING BTREE
);

说明：创建一个数据库，然后运行上述sql语句，生成用户表，主要就下面四个字段

id 用户id 自增主键
username 用户名
password 密码
create_time 创建时间

5.2 修改application.properties配置文件

# 应用名称
spring.application.name=spring-boot-demo
server.port=8888
# 数据库相关
spring.datasource.url=jdbc:mysql://localhost:3306/demo?useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai&useSSL=false
spring.datasource.username=root
spring.datasource.password=123456
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
# mybatis相关
mybatis.mapper-locations=classpath:mapper/*Mapper.xml

说明：

数据库地址 localhost:3306/demo， demo就是数据库名称
数据库用户名 spring.datasource.username
数据库密码 spring.datasource.password
mybatis.mapper-locations 配置扫码xml文件

六、逻辑代码

SpringBootDemoApplication 类

package com.llh.springbootdemo;

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

/**
 * @author llh
 */
@SpringBootApplication
@MapperScan(value = "com.llh.springbootdemo.mapper")
public class SpringBootDemoApplication {

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

}

说明：启动类上加上

@MapperScan(value = "com.llh.springbootdemo.mapper")

作用是扫描到mapper里面中的类，注意路径要和项目中实际路径一致

UserInfo 类

package com.llh.springbootdemo.entity;

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

import java.time.LocalDateTime;

/**
 * @author llh
 */
public class UserInfo {
    @TableId(value = "id", type = IdType.AUTO)
    private Long id;
    private String username;
    private String password;
    private LocalDateTime createTime;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public LocalDateTime getCreateTime() {
        return createTime;
    }

    public void setCreateTime(LocalDateTime createTime) {
        this.createTime = createTime;
    }

    @Override
    public String toString() {
        return "UserInfo{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", createTime=" + createTime +
                '}';
    }
}

说明：这里类成员变量和数据库字段对应，Mybatis自动做了驼峰法到下划线的转换
如：数据库 create_time -> 类变量 createTime

UserInfoMapper 类

package com.llh.springbootdemo.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.llh.springbootdemo.entity.UserInfo;

/**
 * @author llh
 */
public interface UserInfoMapper extends BaseMapper<UserInfo> {
}

说明：BaseMapper 类封装了dao层基本的增删改查操作

mapper/UserInfoMapper.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.llh.springbootdemo.mapper.UserInfoMapper">

</mapper>

说明：这里的namespace和上述的UserInfoMapper路径对应一致

UserInfoService 类

package com.llh.springbootdemo.service;

import com.baomidou.mybatisplus.extension.service.IService;
import com.llh.springbootdemo.entity.UserInfo;

/**
 * @author llh
 */
public interface UserInfoService extends IService<UserInfo> {
}

说明：这里IService封装了service层基本的增删改查

UserInfoServiceImpl 类

package com.llh.springbootdemo.service.impl;

import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.llh.springbootdemo.entity.UserInfo;
import com.llh.springbootdemo.mapper.UserInfoMapper;
import com.llh.springbootdemo.service.UserInfoService;
import org.springframework.stereotype.Service;

/**
 * @author llh
 */
@Service
public class UserInfoServiceImpl extends ServiceImpl<UserInfoMapper, UserInfo> implements UserInfoService {
}

UserInfoController 类

package com.llh.springbootdemo.controller;

import com.llh.springbootdemo.entity.UserInfo;
import com.llh.springbootdemo.service.UserInfoService;
import org.springframework.web.bind.annotation.*;

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

/**
 * @author llh
 */
@RestController
@RequestMapping("/userInfo")
public class UserInfoController {
    @Resource
    private UserInfoService userInfoService;

    @PostMapping("/add")
    public Boolean add(@RequestBody UserInfo userInfo) {
        userInfo.setCreateTime(LocalDateTime.now());
        return userInfoService.save(userInfo);
    }

    @GetMapping("/delete/{id}")
    public Boolean delete(@PathVariable Long id) {
        return userInfoService.removeById(id);
    }

    @PostMapping("/update")
    public Boolean update(@RequestBody UserInfo userInfo) {
        return userInfoService.updateById(userInfo);
    }

    @GetMapping("/get/{id}")
    public UserInfo get(@PathVariable Long id) {
        return userInfoService.getById(id);
    }

    @GetMapping("/list")
    public List<UserInfo> list() {
        return userInfoService.list();
    }

}