引言

看到很多项目都使用MyBatis，所以准备学一下。这里的笔记是我的学习纪要，有网上资料，有学习视频，也有自己在学习过程中的思考。但是代码都是我自己手写的。

为什么要学习MyBatis？

数据库操作的工具分析

MyBatis的优势

SpringBoot 集成 MyBatis

第一步：新建Module

pom.xml有如下依赖：

  <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.3.2</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

第二步：准备工作

application.properties配置如下：

spring.datasource.url=jdbc:mysql://localhost:3306/mybatis_demo
spring.datasource.username=root
spring.datasource.password=xfsy2018
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

mybatis.type-aliases-package=com.fengwenyi.demo1.entity
mybatis.mapper-locations=classpath:mapper/*.xml

再建如下目录结构

目录结构

建数据库：

DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) DEFAULT NULL,
  `age` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=8 DEFAULT CHARSET=utf8mb4;

第三步：下面我们以查询为例

User

package com.fengwenyi.demo1.entity;

/**
 * @author Wenyi Feng
 */
public class User {

    private Long id;
    private String name;
    private Integer age;
    // getter and setter 
    // toString
}

UserMapper

<?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.fengwenyi.demo1.dao.UserDao" >
    <resultMap id="BaseResultMap" type="com.fengwenyi.demo1.entity.User" >
        <id column="id" property="id" jdbcType="BIGINT" />
        <result column="name" property="name" jdbcType="VARCHAR" />
        <result column="age" property="age" jdbcType="INTEGER" />
    </resultMap>

    <select id="findById" resultMap="BaseResultMap" parameterType="java.lang.Long" >
        SELECT
          id, name, age
        FROM
          user
        WHERE
          id = #{id, jdbcType=BIGINT}
    </select>
</mapper>

UserDao

package com.fengwenyi.demo1.dao;

import com.fengwenyi.demo1.entity.User;
import org.apache.ibatis.annotations.Mapper;

/**
 * @author Wenyi Feng
 */
@Mapper
public interface UserDao {
    User findById (Long id);
}

UserService

package com.fengwenyi.demo1.service;

import com.fengwenyi.demo1.dao.UserDao;
import com.fengwenyi.demo1.entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

/**
 * @author Wenyi Feng
 */
@Service
public class UserService {

    @Autowired
    private UserDao userDao;

    public User findById (Long id) {
        return userDao.findById(id);
    }
}

到这里准备工作就算完成了，这里值得一提的是，service的作用会到这么体现出来，下面来看下测试代码。

Test

我是在Spring Boot提供的测试代码中进行测试的：

package com.fengwenyi.demo1;

import com.fengwenyi.demo1.entity.User;
import com.fengwenyi.demo1.service.UserService;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

@RunWith(SpringRunner.class)
@SpringBootTest
public class Demo1ApplicationTests {

    @Autowired
    private UserService userService;

    @Test
    public void contextLoads() {


    }

    @Test
    public void findById () {
        User user = userService.findById(1L);

        System.out.println(user.toString());
    }
}

资料

我已将我的代码放至 Github

我们一起学习，一起进步吧！！！