SpringBoot——整合MyBatis实现CRUD

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：

SpringBoot——整合MyBatis实现CRUD
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：

SpringBoot——整合MyBatis实现CRUD
选中userdao中要进行测试的方法：

SpringBoot——整合MyBatis实现CRUD
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：

SpringBoot——整合MyBatis实现CRUD

SpringBoot——整合MyBatis实现CRUD

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