SpringBoot 整合 MyBatis（附上查询用户案例）

步骤

运行环境：

• IdeaU 2021.1
• MySQL 5.7
• JDK 11

1. 在Spring 官网提供的在线生成器，生成 SpringBoot 项目，下载解压

   地址：https://start.spring.io/

   选择JDK，填写相关信息，添加 JDBC依赖，MySQL驱动依赖，SpringWeb依赖

   Group:com.serious
   Artifact:springboot-mybatis
   Name:springboot-mybatis
   Description:Demo
   Package name:com.serious
   Packaging:Jar
   JDK:11
   

点击Generate，下载生成的文件

2. IDEA打开解压的项目

   在Maven仓库找到 mybatis整合SpringBoot的依赖：

   <!--	 mybatis-spring-boot-starter: 整合	-->
   		<!-- https://mvnrepository.com/artifact/org.mybatis.spring.boot/mybatis-spring-boot-starter -->
   		<dependency>
   			<groupId>org.mybatis.spring.boot</groupId>
   			<artifactId>mybatis-spring-boot-starter</artifactId>
   			<version>2.1.4</version>
   		</dependency>
   

   写到项目的pom.xml文件中

3. 创建数据库springboot_mybatis

   create database springboot_mybatis;
   use springboot_mybatis;
   

   创建 user 表

   create table `user`(
       id int primary key ,
       `name` varchar(20),
       pwd varchar(20)
   );
   

   向 user 表中插入数据

   insert into user(id, `name`, pwd)
   values (1, '刘备', 'lb');
   insert into user(id, `name`, pwd)
   values (2, '孙尚香', 'ssx');
   insert into user(id, `name`, pwd)
   values (3, '孙权', 'sq');
   

4. 编写数据库连接

   打开application.properties文件，顺便在resources目录下新建一个文件夹名为mybatis，然后在mybatis文件夹下再建一个文件夹，名为mapper，后面写的XXXmapper.xml文件就应该放到这个目录下

   # 配置数据库连接
   spring.datasource.username=root
   spring.datasource.password=root
   spring.datasource.url=jdbc:mysql://localhost:3306/springboot_mybatis?useUnicode=true&characterEncoding=utf-8
   spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
   
   # mybatis 整合
   # 设置别名
   mybatis.type-aliases-package=com.serious.pojo
   # 扫描mapper对应的xml文件
   mybatis.mapper-locations=classpath:mybatis/mapper/*.xml
   
   

5. 编写测试类

   package com.serious;
   
   import org.junit.jupiter.api.Test;
   import org.springframework.beans.factory.annotation.Autowired;
   import org.springframework.boot.test.context.SpringBootTest;
   
   import javax.sql.DataSource;
   
   @SpringBootTest
   class SpringbootMybatisApplicationTests {
   
   	@Autowired
   	DataSource dataSource;
   
   	@Test
   	void contextLoads() {
   		System.out.println("数据源是：" + dataSource.getClass());
   
   	}
   
   }
   
   

6. 运行测试类
   

7. 在com.serious包下创建一个pojo包
   在pojo包下创建一个User类

package com.serious.pojo;

public class User {

    private Integer id;
    private String name;
    private String pwd;

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

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

8. 在com.serious包下创建一个mapper包，
   在mapper包下新建一个UserMapper接口

package com.serious.mapper;

import com.serious.pojo.User;
import org.apache.ibatis.annotations.Mapper;
import org.springframework.stereotype.Repository;

import java.util.List;

@Mapper
@Repository
public interface UserMapper {

    // 查询所有用户
    public List<User> queryAllUser();
}

9. 在resources文件夹下的mapper文件夹新建一个UserMapper.xml文件

<?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.serious.mapper.UserMapper">

    <select id="queryAllUser" resultType="User">
        select * from user
    </select>

</mapper>

10. 在com.serious包下创建一个service包，
    在service包下新建一个UserService接口和UserServiceImpl类

package com.serious.service;

import com.serious.pojo.User;

import java.util.List;

public interface UserService {

    // 查询所有用户
    public List<User> queryAllUser();
}

UserServiceImpl类

package com.serious.service;

import com.serious.mapper.UserMapper;
import com.serious.pojo.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class UserServiceImpl implements UserService{

    @Autowired
    UserMapper userMapper;

    @Override
    public List<User> queryAllUser() {
        return userMapper.queryAllUser();
    }
}

11.编写测试类

package com.serious;

import com.serious.pojo.User;
import com.serious.service.UserServiceImpl;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.List;

@SpringBootTest
class SpringbootMybatisApplicationTests {

	@Autowired
	UserServiceImpl userService;

	@Test
	void contextLoads() {

		List<User> userList = userService.queryAllUser();
		for (User user : userList){
			System.out.println(user);
		}

	}

}

12. 结果

User{id=1, name='刘备', pwd='lb'}
User{id=2, name='孙尚香', pwd='ssx'}
User{id=3, name='孙权', pwd='sq'}