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>

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>
        <!-- 获取数据库自增id -->
        <setting name="useGeneratedKeys" value="true"/>

        <!-- 支持别名 -->
        <setting name="useColumnLabel" value="true" />

        <!-- 支持驼峰命名转换，例如表字段create_time 对应实体类的createTime属性 -->
        <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：

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：

选中userdao中要进行测试的方法：

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：