springboot 整合mybatis

springboot 整合mybatis

1.先说遇到的问题

controller层启动一直包空指针的错误，看了这篇文章才明白！ 链接：http://t.csdn.cn/q3vbH
解决方法：在类上添加注解！

@SpringBootTest注解是SpringBoot自1.4.0版本开始引入的一个用于测试的注解。
@RunWith(SpringRunner.class)在正常情况下测试类是需要@RunWith的，作用是告诉java你这个类通过用什么运行环境运行，例如启动和创建spring的应用上下文。否则你需要为此在启动时写一堆的环境配置代码。你在IDEA里去掉@RunWith仍然能跑是因为在IDEA里识别为一个JUNIT的运行环境，相当于就是一个自识别的RUNWITH环境配置。但在其他IDE里并没有。
原文链接：https://blog.youkuaiyun.com/qq_21108099/article/details/111496005
9

2.先添加依赖

 <!--   mysql -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.0.5</version>
        </dependency>
        <!--   引入mybatis 官方提供适配springboot的    -->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.1.0</version>
        </dependency>

3.application.yml的配置文件

#配置mybatis的xml位置!
#我的在resource/mapper/*.xml
mybatis:
  mapper-locations: classpath:mapper/*.xml

4.编写三层架构

①实体类

package com.me.modules.userinfo.domain;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;


/**
 * Description: .实体类
 * Date:        2022/6/2 22:12
 * author:      chuliujian
 * version:     V1.0
 */
@Data
@AllArgsConstructor//带全参的构造器
@NoArgsConstructor//无参
@ToString
public class User {
    private Integer id;
    private String username;

}

②mapper层

package com.me.modules.userinfo.mapper;

import com.me.modules.userinfo.domain.User;
import org.apache.ibatis.annotations.Mapper;
import org.springframework.stereotype.Repository;

/**
 * Description: .
 * Date:        2022/6/2 22:11
 * author:      chuliujian
 * version:     V1.0
 */
@Mapper
@Repository
public interface UserMapper {

      /**
       * 根据id查询用户信息
       * @param id
       * @return
       */
      User getUserInfo(int id);
}

mapper.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的位置-->
<mapper namespace="com.me.modules.userinfo.mapper.UserMapper">
<!--    id为mapper里面的方法名称,,,,,,,resultType返回类型,,,parameterType参数类型-->
    <select id="getUserInfo" resultType="com.me.modules.userinfo.domain.User">
        select * from usera where id = #{id}
    </select>
</mapper>



<!--<select id="getOrder" parameterType="int" resultMap="orderresultmap">-->
<!--        select * from orders where order_id=#{id}-->
<!--    </select>-->

<!--<resultMap type=”me.gacl.domain.order” id=”orderresultmap”>-->
<!--<!–用id属性来映射主键字段–>-->
<!--<id property=”id” column=”order_id”>-->
<!--<!–用result属性来映射非主键字段，property为实体类属性名，column为数据表中的属性–>-->
<!--<result property = “orderno” column =”order_no”/>-->
<!--<result property=”price” column=”order_price” />-->
<!--        </reslutMap>-->

③Service层

impl实现类

package com.me.modules.userinfo.service.impl;

import com.me.modules.userinfo.domain.User;
import com.me.modules.userinfo.mapper.UserMapper;
import com.me.modules.userinfo.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;

/**
 * Description: .
 * Date:        2022/6/2 22:21
 * author:      chuliujian
 * version:     V1.0
 */
@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserMapper userMapper;


    @Override
    public User getUserInfoservice(int id) {
        return userMapper.getUserInfo(id);
    }
}

④controller控制层—调用service空指针问题:http://t.csdn.cn/q3vbH

package com.me.modules.userinfo.rest;

import com.me.modules.userinfo.domain.User;
import com.me.modules.userinfo.service.UserService;
import com.me.modules.userinfo.service.impl.UserServiceImpl;
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;

/**
 * Description: .
 * 调用空指针问题:http://t.csdn.cn/q3vbH
 * Date:        2022/6/2 22:23
 * author:      chuliujian
 * version:     V1.0
 */
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserInfoController {

    @Autowired
    private  UserService userService;


    @Test
    public void getuserinfo(){
        User userInfoservice = userService.getUserInfoservice(1);
        System.out.println(userInfoservice);
    }
}