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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 40
javamybatis源码解析

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=true&amp;characterEncoding=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=true&amp;characterEncoding=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=true&amp;characterEncoding=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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