新建 SpringBoot 项目 springboot_mybatis

添加 Mybatis 的起步依赖

<!--mybatis起步依赖-->
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>1.1.1</version>
</dependency>
<!-- MySQL连接驱动 -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
</dependency>

添加数据库连接信息

在 application.yml 中添加数据量的连接信息

mybatis:
  # 指定mybatis别名包
  type-aliases-package: com.atguigu.domain
  # 指定xml映射文件路径
  mapper-locations: classpath:com/atguigu/dao/*.xml
logging:
  level:
    # 配置日志
    com.atguigu.dao: debug
spring:
  datasource:
    username: root
    password: root
    url: jdbc:mysql://192.168.88.88:3306/springboot?useUnicode=true&characterEncoding=utf8
    driver-class-name: com.mysql.cj.jdbc.Driver
server:
  port: 1888

创建 user 表

创建名叫springboot数据库，

数据库中新建user表

DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(50) DEFAULT NULL,
  `password` varchar(50) DEFAULT NULL,
  `name` varchar(50) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=10 DEFAULT CHARSET=utf8;


INSERT INTO `user` VALUES ('1', 'zhangsan', '123', '张三');
INSERT INTO `user` VALUES ('2', 'lisi', '123', '李四');

创建实体 Bean

package com.atguigu.domain;

import java.io.Serializable;

/**
 * @author: ShiGuang
 * @create: 2021-06-09 21:21
 * @description:
 */
public class User implements Serializable {
    // 主键
    private Long id;
    // 用户名
    private String username;
    // 密码
    private String password;
    // 姓名
    private String name;

    //省略各种方法 .. ..
}

创建 Controller

package com.atguigu.controller;

import com.atguigu.domain.User;
import com.atguigu.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

/**
 * @author: ShiGuang
 * @create: 2021-06-09 21:24
 * @description:
 */
@RestController
@RequestMapping("/user")
public class UserController {

    @Autowired
    private UserService userService;


    @RequestMapping("/findAll")
    private List<User> findAll() {
        return userService.findAll();
    }

}

创建 Service

package com.atguigu.service;

import com.atguigu.domain.User;

import java.util.List;

/**
 * @author: ShiGuang
 * @create: 2021-06-09 21:25
 * @description:
 */
public interface UserService {
    List<User> findAll();
}

创建实现类

package com.atguigu.service;

import com.atguigu.dao.UserDao;
import com.atguigu.domain.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

/**
 * @author: ShiGuang
 * @create: 2021-06-09 21:25
 * @description:
 */
@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserDao userDao;

    @Override
    public List<User> findAll() {
        return userDao.findAll();
    }
}

创建 Dao

package com.atguigu.dao;

import com.atguigu.domain.User;
import org.apache.ibatis.annotations.Mapper;

import java.util.List;

// @Mapper标记该类是一个mybatis的mapper接口，可以被spring boot自动扫描到spring上下文中
@Mapper
public interface UserDao {
    List<User> findAll();
}

编写 Mapper

注意，Mapper 要放到resources下与 UserDao 对应的目录！

比如resources\com\atguigu\dao\UserDao.xml与java\com\atguigu\dao\UserDao.java对应

<?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.atguigu.dao.UserDao">
    <select id="findAll" resultType="user">
        select * from user
    </select>
</mapper>