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MyBatis——源码解析MyBatis框架底层的执行原理

杰森wang 2022-06-20 阅读 39

文章目录:

1.前言

2.案例项目源码

3.MyBatis源码解析底层执行原理

3.1 读取mybatis配置文件创建出SqlSeesionFactory对象

3.2 通过SqlSeesionFactory对象进而创建出SqlSession对象

3.3 通过SqlSession的getMapper获取到接口代理对象

3.4 通过mapper接口的代理对象执行CRUD


1.前言


2.案例项目源码

<dependencies>
<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>

<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.20</version>
</dependency>

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

<build>
<!--资源插件:处理src/main/java目录中的xml-->
<resources>
<resource>
<directory>src/main/java</directory><!--所在的目录-->
<includes><!--包括目录下的.properties,.xml 文件都会扫描到-->
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>false</filtering>
</resource>
</resources>
</build>
package com.szh.entity;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

/**
*
*/

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Student {
private Integer id;
private String name;
private Integer age;
private String email;
}

package com.szh.dao;

import com.szh.entity.Student;

import java.util.List;

/**
*
*/

public interface StudentDao {

List<Student> selectAll();

}
<?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.szh.dao.StudentDao">

<sql id="column">
id, name, age, email
</sql>

<select id="selectAll" resultType="com.szh.entity.Student">
select <include refid="column"></include>
from student
</select>

</mapper>
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/ssm?useUnicode=truecharacterEncoding=utf-8
jdbc.username=root
jdbc.password=12345678
<?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>
<properties resource="jdbc.properties" />

<!--设置日志-->
<settings>
<setting name="logImpl" value="STDOUT_LOGGING"/>
</settings>

<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<!--配置数据源:创建Connection对象-->
<dataSource type="POOLED">
<!-- driver:驱动内容 -->
<property name="driver" value="${jdbc.driver}"/>
<!-- 连接数据库的url -->
<property name="url" value="${jdbc.url}"/>
<!-- 用户名 -->
<property name="username" value="${jdbc.username}"/>
<!-- 密码 -->
<property name="password" value="${jdbc.password}"/>
</dataSource>
</environment>
</environments>

<mappers>
<mapper class="com.szh.dao.StudentDao"/>
<!-- <package name="com.szh.dao"/>-->
</mappers>
</configuration>
package com.szh.utils;

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 java.io.IOException;
import java.io.InputStream;

/**
* 工具类:创建SqlSession对象
*/

public class MyBatisUtil {

private static SqlSessionFactory factory = null;

static {
String config = "mybatis.xml";
try {
InputStream inputStream = Resources.getResourceAsStream(config);
factory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
}

public static SqlSession getSqlSession() {
SqlSession session = null;
if (factory != null) {
session = factory.openSession();
}
return session;
}
}
package com.szh;

import com.szh.dao.StudentDao;
import com.szh.entity.Student;
import com.szh.utils.MyBatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

/**
*
*/

public class MyTest {

@Test
public void testSelectStudents() {
SqlSession session = MyBatisUtil.getSqlSession();
StudentDao studentDao = session.getMapper(StudentDao.class);
//com.sun.proxy.$Proxy == StudentDaoImpl
System.out.println("studentDao === " + studentDao.getClass().getName());
List<Student> studentList = studentDao.selectAll();
studentList.forEach(stu-> System.out.println("stu = " + stu));
session.close();
}

}


3.MyBatis源码解析底层执行原理

3.1 读取mybatis配置文件创建出SqlSeesionFactory对象

<configuration>
<properties resource="jdbc.properties"/>

<settings>
<setting name="logImpl" value="STDOUT_LOGGING"/>
</settings>

<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driver}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</dataSource>
</environment>
</environments>

<mappers>
<mapper class="com.szh.dao.StudentDao"/>
</mappers>
</configuration>

<properties resource="jdbc.properties"/>

<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/ssm?useUnicode=truecharacterEncoding=utf-8"/>
<property name="username" value="root"/>
<property name="password" value="12345678"/>
</dataSource>
</environment>
</environments>

<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/ssm?useUnicode=truecharacterEncoding=utf-8"/>
<property name="username" value="root"/>
<property name="password" value="12345678"/>
</dataSource>

<mappers>
<mapper class="com.szh.dao.StudentDao"/>
</mappers>

3.2 通过SqlSeesionFactory对象进而创建出SqlSession对象

3.3 通过SqlSession的getMapper获取到接口代理对象

3.4 通过mapper接口的代理对象执行CRUD

 

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