基于 IDEA 搭建 Spring Boot + MyBatis + MySQL 工程实践

2. 实体类定义

实体类命名建议遵循 Java 规范（首字母大写），字段名与数据库列对应。

package com.example.springboot.entity;

import org.apache.ibatis.annotations.Mapper;

@Mapper
public class User {
    private String userID;
    private String userName;
    private String userPassword;
    private Integer userAge;

    // Getters and Setters
    public String getUserID() { return userID; }
    public void setUserID(String userID) { this.userID = userID; }
    public String getUserName() { return userName; }
    public void setUserName(String userName) { this.userName = userName; }
    public String getUserPassword() { return userPassword; }
    public void setUserPassword(String userPassword) { this.userPassword = userPassword; }
    public Integer getUserAge() { return userAge; }
    public void setUserAge(Integer userAge) { this.userAge = userAge; }
}

3. Mapper 接口与 XML 映射

定义 Mapper 接口，并在对应的 XML 文件中编写 SQL 语句。

package com.example.springboot.mapper;

import com.example.springboot.entity.User;
import java.util.List;

public interface UserMapper {
    List<User> selectAll();
}

XML 映射文件 (UserMapper.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.example.springboot.mapper.UserMapper">
    <select id="selectAll" resultType="com.example.springboot.entity.User">
        SELECT * FROM user_list
    </select>
</mapper>

提示：安装 IDEA 插件 MyBatisX 可以更方便地查看 Mapper 方法与 XML 的关联关系。

4. Service 层实现

业务逻辑层负责调用 Mapper 并处理业务规则。

package com.example.springboot.service;

import com.example.springboot.mapper.UserMapper;
import com.example.springboot.entity.User;
import jakarta.annotation.Resource;
import org.springframework.stereotype.Service;
import java.util.List;

@Service
public class UserService {
    @Resource
    private UserMapper userMapper;

    public List<User> selectAll() {
        return userMapper.selectAll();
    }
}

5. Controller 层暴露接口

控制层接收请求并返回统一格式的结果。

package com.example.springboot.controller;

import com.example.springboot.common.Result;
import com.example.springboot.service.UserService;
import com.example.springboot.entity.User;
import jakarta.annotation.Resource;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.List;

@RestController
@RequestMapping("/user")
public class UserController {
    @Resource
    private UserService userService;

    @GetMapping("/selectAll")
    public Result selectAll() {
        List<User> list = userService.selectAll();
        return Result.success(list);
    }
}

6. 启动配置

在主启动类上添加 @MapperScan 注解，指定 Mapper 接口的扫描路径，避免在每个 Mapper 接口上加 @Mapper 注解。

@SpringBootApplication
@MapperScan("com.example.springboot.mapper")
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

完成上述配置后，启动项目即可访问 http://localhost:9090/user/selectAll 获取用户列表数据。