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第一次学习mybatis，根据步骤完成CURD操作。

## 使用Idea创建一个Module

![](https://www.1024phper.com/wp-content/uploads/2021/03/QQ截图20210330192128.jpg)

![](https://www.1024phper.com/wp-content/uploads/2021/03/QQ截图20210330192208.jpg)

![](https://www.1024phper.com/wp-content/uploads/2021/03/QQ截图20210330192229.jpg)

![](https://www.1024phper.com/wp-content/uploads/2021/03/QQ截图20210330192240.jpg)

![](https://www.1024phper.com/wp-content/uploads/2021/03/QQ截图20210330192317.jpg)

## 配置pom.xml文件

### 加入依赖项

加入mysql的驱动以及mybatis依赖

```
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.1</version>
</dependency>
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.9</version>
</dependency>
```

### 加入resources配置项

加入该配置项的意义是使编译器，main/java目录下的配置文件会被拷贝到编译目录中（默认main/java目录下的非.java文件不会被拷贝）

```xml
<resources>
  <resource>
    <directory>src/main/java</directory>
    <includes>
      <include>**/*.properties</include>
      <include>**/*.xml</include>
    </includes>
    <filtering>false</filtering>
  </resource>
</resources>
```

pom.xml的内容如下：

```xml
<?xml version="1.0" encoding="UTF-8"?>

<groupId>com.learnmybatis</groupId>
  <artifactId>day2</artifactId>
  <version>1.0-SNAPSHOT</version>

<dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>

<dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.5.1</version>
    </dependency>
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.9</version>
    </dependency>
  </dependencies>

<build>
    <resources>
      <resource>
        <directory>src/main/java</directory>
        <includes>
          <include>**/*.properties</include>
          <include>**/*.xml</include>
        </includes>
        <filtering>false</filtering>
      </resource>
    </resources>
  </build>
</project>
```

## 准备数据表及编写pojo类

User表结构如下：

```java
id	    int(10)	NO	 PRI		auto_increment
name	varchar(64)	 NO			
email	varchar(255) NO			
age	    int(3)	     NO		0	
```

在java/com/learnmybatis/目录下新建包pojo，然后编写User.java

## 创建Mybatis的主配置文件

在resources目录下创建mybatis.xml文件

```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>

<environment id="online">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        
        <mapper resource="com/learnmybatis/dao/user.xml"/>
    </mappers>
</configuration>
```

## 创建Mapper映射文件user.xml

在main/java/com/learnmybits/dao/目录下创建user.xml

```xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.learnmybatis.dao.user">
    <select id="select" resultType="com.learnmybatis.pojo.User">
        select * from `user`
    </select>

<select id="selectById" resultType="com.learnmybatis.pojo.User">
        select * from `user` WHERE id=#{id}
    </select>

<update id="updateById">
        UPDATE `user` SET `name` = #{name},`email` = #{email}, `age` = #{age} WHERE id=#{id}
    </update>

<insert id="insert">
        INSERT `user`(`name`, `email`,`age`) VALUE(#{name}, #{email}, #{age})
    </insert>

<delete id="delete">
        DELETE FROM `user` WHERE id=#{id}
    </delete>
</mapper>
```

## 创建测试文件测试CURD

```java
package com.learnmybatis;

import com.learnmybatis.pojo.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

/**
 * @author monkeykingGWX
 * email 704835519@qq.com
 * created 2021-03-30 20:13
 */

public class TestMybatis {

@Test
    public void testSelect () throws IOException {
        String            resource          = "mybatis.xml";
        InputStream       inputStream       = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

// mybatis默认不是自动提交事务的，这里设置为true，相当于设置autoCommit(true)
        try (SqlSession session = sqlSessionFactory.openSession(true)) {
            String     sqlId = "com.learnmybatis.dao.user.select";
            List<User> users = session.selectList(sqlId);
            users.forEach(System.out::println);
        }
    }

@Test
    public void testSelectById () throws IOException
    {
        String            resource          = "mybatis.xml";
        InputStream       inputStream       = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

try (SqlSession session = sqlSessionFactory.openSession(true)) {
            String     sqlId = "com.learnmybatis.dao.user.selectById";
            User user = session.selectOne(sqlId, 1);

System.out.println(user);
        }
    }

@Test
    public void testInsert () throws IOException
    {
        String            resource          = "mybatis.xml";
        InputStream       inputStream       = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

try (SqlSession session = sqlSessionFactory.openSession(true)) {
            String     sqlId = "com.learnmybatis.dao.user.insert";
            int        n   = session.insert(sqlId, new User(null, "周杰伦", "JayZhou@163.com", 40));
            System.out.println(n);
        }
    }

@Test
    public void testUpdate () throws IOException
    {
        String            resource          = "mybatis.xml";
        InputStream       inputStream       = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

try (SqlSession session = sqlSessionFactory.openSession(true)) {
            String     sqlId = "com.learnmybatis.dao.user.updateById";
            int    n   = session.update(sqlId, new User(2, "周杰伦&Jay", "JayZhou@qq.com", 36));
            System.out.println(n);
        }
    }

@Test
    public void testDelete () throws IOException
    {
        String            resource          = "mybatis.xml";
        InputStream       inputStream       = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

try (SqlSession session = sqlSessionFactory.openSession(true)) {
            String     sqlId = "com.learnmybatis.dao.user.delete";
            int    n   = session.delete(sqlId, 2);
            System.out.println(n);
        }
    }
}
```

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