4、集成mybatis-plus与lombok实现查询Mysql数据并返回

1. 添加依赖 pom.xml

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <scope>runtime</scope>
</dependency>
<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.5.3.1</version>
</dependency>
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.24</version>
    <scope>provided</scope>
</dependency>

2. 添加数据库连接配置 src/main/resources/application.yml

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/{数据库名}?useUnicode=true&characterEncoding=utf-8&serverTimezone=GMT%2B8
    username: {账号}
    password: {密码}
    hikari:
      connection-init-sql: set names utf8mb4 # 使用utf8mb4字符集
  mvc:
    pathmatch:
      matching-strategy: ant_path_matcher # 配置这个来防止swagger报错

因为要使用utf8mb4编码，因此配置了connection-init-sql，在characterEncoding直接配置成utf8mb4会报错

3. 创建实体类，用于存储查询出来的数据

src/main/java/com/lazysleep/base/entity/User.java

package com.lazysleep.base.entity;


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

@Data
@TableName("u_user")
public class User {

    @TableId(value = "id", type = IdType.AUTO)
    private Integer id;
    private String name;
    private Integer age;
    private String email;
}

涉及到三个注解

• @Data：对类成员变量增加 get set 方法
• @TableName：对应数据库表名
• @TableId：标记主键

mybatis-plus更多内容见 简介 | MyBatis-Plus (baomidou.com)

4. 创建Mapper src/main/java/com/lazysleep/base/mapper/UserMapper.java

package com.lazysleep.base.mapper;

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

@Repository
public interface UserMapper extends BaseMapper<User> {

}

5. 在入口文件添加MapperScan注解

package com.lazysleep.base;

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

@SpringBootApplication
@MapperScan("com.lazysleep.base")
public class BaseApplication {

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

}

此注解需要传入一个包名，作为扫描起点，如过不添加，后续mapper无法注入

6. 改造原来的FooController

package com.lazysleep.base.controller;


import com.lazysleep.base.entity.User;
import com.lazysleep.base.mapper.UserMapper;
import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;


@Api(tags = "Foo控制器")
@RestController
@RequestMapping("/foo")
public class FooController {

    @Autowired
    private UserMapper userMapper;

    @GetMapping("foo")
    @ApiOperation(value = "Foo接口")
    public User foo() {
        return userMapper.selectById(1);
    }

}

使用@Autowired注入UserMapper实例，并在方法中调用selectById方法查询数据库用户表id=1的用户数据并返回。