SpringBoot——整合MyBatis實現CRUD

SpringBoot項目的持久層一般都是使用JPA或者MyBatis，我個人是比較喜歡MyBatis。

首先我們打開pom.xml，添加上mybatis需要的一些依賴

<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下創建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>
        <!-- 獲取數據庫自增id -->
        <setting name="useGeneratedKeys" value="true"/>

        <!-- 支持別名 -->
        <setting name="useColumnLabel" value="true" />

        <!-- 支持駝峯命名轉換，例如表字段create_time 對應實體類的createTime屬性 -->
        <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 '用戶名',
  `create_time` datetime DEFAULT NULL COMMENT '創建時間',
  `update_time` datetime DEFAULT NULL COMMENT '修改時間',
  PRIMARY KEY (`user_id`)
) ENGINE=MyISAM AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;
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創建對應的實體類：

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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創建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目錄下創建mybatis目錄，用於存放mapper文件，整體目錄結構如下： 

在application.yml配置文件中配置數據庫連接信息和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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編寫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啓動類，加上@MapperScan 註解

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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下面進行測試，打開UserDao，點擊接口名UserDao，然後按alt+回車，點擊create test： 

選中userdao中要進行測試的方法： 

選擇確定，然後會自動創建UserDaoTest，編寫測試方法然後右鍵，點擊run執行測試方法

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:

要給測試類加上@RunWith 和 @SpringBootTest 註解
如果你用的是IDEA，那麼在Autowired UserDao時，可能會提示錯誤，原因是找不到對應的bean。UserDao是接口，找不到bean是正常的，可以不用管這個錯誤，運行時是不會報錯的。如果你想把錯誤提示去掉，可以在setting設置中錯誤級別從Error改爲Warning，具體見下圖：