MyBatis 读取MySQL 数据简单示例

1.确定需求、

  输入：前端访问http://localhost:8080/hello

  输出：前端显示后端从数据库读取的数据

2.新建项目的子模块

新建模块mybatis

3.MySQL 数据库配置、添加数据

创建数据库，  添加表， 添加表的字段， 添加数据

4.编写代码

新建controller、service、mapper、domain 包

新建mapper 资源目录

  新建controller、service、mapper、domain 对应的Java 文件

  新建mapper 资源目录Java mapper 对应的XML 文件

controller

import com.example.mybatis.domain.User;
import com.example.mybatis.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
public class HelloController {
    @Autowired
    private UserService userService;

    @GetMapping("/hello")
    public List<User> hello()
    {
        return userService.selectAllUser();
    }
}

 service

public class User {
    public int id;
    private String name;
    private int age;
    public String sex;
    public String createTime;

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getId() {
        return id;
    }

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

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getCreateTime() {
        return createTime;
    }

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

    @Override
    public String toString(){
        return "User{"+
                "id="+id+
                ", name '" + name + '\''+
                ", age="+ age+
                ", sex="+ sex+
                ",createTime='" + createTime +'\''+
                '}';
    }
}

 mapper

import com.example.mybatis.domain.User;

import java.util.List;

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

domain

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

@SpringBootApplication
@MapperScan("com.example.mybatis.mapper")
public class MybatisApplication {

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

}

5.编译代码、构建程序、执行SpringBoot 程序

7.测试SpringBoot 后端接口