SpringBoot——整合MyBatis实现CRUD

红太狼 2022-02-20 06:57 327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>  
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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">

<setting name="useColumnLabel" value="true" />

<setting name="mapUnderscoreToCamelCase" value="true" />  
    </settings>  
</configuration>  
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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;  
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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;  
    \}  
\}  
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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);

\}  
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resources目录下创建mybatis目录，用于存放mapper文件，整体目录结构如下：

![è¿éåå¾çæè¿°][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  
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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>  
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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);  
    \}  
\}  
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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：

![è¿éåå¾çæè¿°][70 1]  
选中userdao中要进行测试的方法：

![è¿éåå¾çæè¿°][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);  
    \}  
\}  
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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：

![è¿éåå¾çæè¿°][70 3]

[70]: /images/20220220/16805573b03c4b7c95370f7780455165.png
[70 1]: /images/20220220/5028796d6ef94e59a53bec3a65054973.png
[70 2]: /images/20220220/11f32c048b8443acba2c22b76f2ccd1f.png
[70 3]: /images/20220220/0753d6b599dd43349c9601a5c26023e5.png