SpringBoot——整合MyBatis实现CRUD

骑猪看日落 2022-05-24 00:57 276阅读 0赞

SpringBoot项目的持久层一般都是使用JPA或者MyBatis，我个人是比较喜欢MyBatis。

首先我们打开pom.xml，添加上mybatis需要的一些依赖

<dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
    </dependency>
    
    <dependency>
        <groupId>org.mybatis.spring.boot</groupId>
        <artifactId>mybatis-spring-boot-starter</artifactId>
        <version>1.3.1</version>
    </dependency>
    
    
    <dependency>
        <groupId>com.mchange</groupId>
        <artifactId>c3p0</artifactId>
        <version>0.9.5.2</version>
    </dependency>

在resources下创建`mybatis-config.xml` ：

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
    
    <configuration>
        <settings>
            
            <setting name="useGeneratedKeys" value="true"/>
    
            
            <setting name="useColumnLabel" value="true" />
    
            
            <setting name="mapUnderscoreToCamelCase" value="true" />
        </settings>
    </configuration>

建表：

CREATE TABLE `t_user` ( `user_id` int(11) NOT NULL AUTO_INCREMENT, `username` varchar(255) DEFAULT '' COMMENT '用户名', `create_time` datetime DEFAULT NULL COMMENT '创建时间', `update_time` datetime DEFAULT NULL COMMENT '修改时间', PRIMARY KEY (`user_id`) ) ENGINE=MyISAM AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;

创建对应的实体类：

package com.example.demo.entity;
    
    import java.util.Date;
    
    public class User { 
    
        private Integer userId;
        private String username;
        private Date createTime;
        private Date updateTime;
    
        public Integer getUserId() {
            return userId;
        }
    
        public void setUserId(Integer userId) {
            this.userId = userId;
        }
    
        public String getUsername() {
            return username;
        }
    
        public void setUsername(String username) {
            this.username = username;
        }
    
        public Date getCreateTime() {
            return createTime;
        }
    
        public void setCreateTime(Date createTime) {
            this.createTime = createTime;
        }
    
        public Date getUpdateTime() {
            return updateTime;
        }
    
        public void setUpdateTime(Date updateTime) {
            this.updateTime = updateTime;
        }
    }

创建Dao：

package com.example.demo.dao;
    
    import com.example.demo.entity.User;
    
    import java.util.List;
    
    public interface UserDao { 
    
        List<User> getAll();
        User find(int userId);
        int insert(User user);
        int delete(int userId);
    
    }

resources目录下创建mybatis目录，用于存放mapper文件，整体目录结构如下：  
![这里写图片描述][70]

在application.yml配置文件中配置数据库连接信息和mybatis

spring:
      datasource:
        driver-class-name: com.mysql.jdbc.Driver
        url: jdbc:mysql://127.0.0.1:3306/demo?useUnicode=true&characterEncoding=UTF-8&autoReconnect=true
        username: root
        password: root
    mybatis:
      config-location: classpath:mybatis-config.xml
      mapper-locations: classpath:mybatis/*Mapper.xml

编写UserMapper.xml文件：

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    
    <mapper namespace="com.example.demo.dao.UserDao">
        <select id="getAll" resultType="com.example.demo.entity.User">
            select * from t_user order by user_id desc
        </select>
    
        <select id="find" resultType="com.example.demo.entity.User">
            select * from t_user where user_id = #{userId}
        </select>
    
        <insert id="insert" useGeneratedKeys="true" keyProperty="userId" keyColumn="user_id" parameterType="com.example.demo.entity.User">
            insert into t_user(username,create_time,update_time) values(#{username},#{createTime},#{updateTime})
        </insert>
    
        <update id="update" parameterType="com.example.demo.entity.User">
           update t_user
           <set>
               <if test="username != null">username=#{username},</if>
               <if test="updateTime != null">update_time=#{updateTime},</if>
           </set>
            where user_id=#{userId}
        </update>
    
        <delete id="delete">
            delete from t_user where user_id=#{userId}
        </delete>
    </mapper>

修改SpringBoot启动类，加上`@MapperScan` 注解

package com.example.demo;
    
    import org.mybatis.spring.annotation.MapperScan;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    
    @SpringBootApplication
    @MapperScan("com.example.demo.dao")
    public class DemoApplication {
    
        public static void main(String[] args) {
            SpringApplication.run(DemoApplication.class, args);
        }
    }

下面进行测试，打开UserDao，点击接口名UserDao，然后按alt+回车，点击create test：  
![这里写图片描述][70 1]

选中userdao中要进行测试的方法：  
![这里写图片描述][70 2]

选择确定，然后会自动创建UserDaoTest，编写测试方法然后右键，点击run执行测试方法

package com.example.demo.dao;
    
    import com.example.demo.entity.User;
    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;
    
    import java.util.Date;
    import java.util.List;
    
    import static org.junit.Assert.*;
    
    @RunWith(SpringRunner.class)
    @SpringBootTest
    public class UserDaoTest { 
    
        @Autowired
        private UserDao userDao;
    
        @Test
        public void getAll() {
            List<User> list = userDao.getAll();
            assertEquals(1,list.size());
        }
    
        @Test
        public void find() {
            User user = userDao.find(1);
            assertEquals("tom",user.getUsername());
        }
    
        @Test
        public void insert() {
            User user = new User();
            user.setUsername("jack");
            user.setCreateTime(new Date());
            int num = userDao.insert(user);
            assertEquals(1,num);
        }
    
        @Test
        public void delete() {
            int num = userDao.delete(1);
            assertEquals(1,num);
        }
    }

注意:

*  要给测试类加上`@RunWith` 和 `@SpringBootTest` 注解
 *  如果你用的是IDEA，那么在Autowired UserDao时，可能会提示错误，原因是找不到对应的bean。UserDao是接口，找不到bean是正常的，可以不用管这个错误，运行时是不会报错的。如果你想把错误提示去掉，可以在setting设置中错误级别从Error改为Warning，具体见下图：

![这里写图片描述][70 3]

[70]: /images/20220524/ea5eeb5bcb5c4b1ebf1a7725ef279508.png
[70 1]: /images/20220524/8049f2dc5033470f9bc5469f2359b797.png
[70 2]: /images/20220524/846e3aae8dcd4d52b20b7c4a90ecfb2f.png
[70 3]: /images/20220524/34f69b85b4b3451a910730df29619b8b.png