Mybatis 源码阅读 (一)

先从一张图说起吧，这个是mybatis源码包的目录。刚开始看只能从名字判断个大概，并不是特别理解，一个一个包来吧。先贴一段代码：

public void Test() throws FileNotFoundException{
        String configLocation = "myBatis-config.xml";
        Reader reader = new FileReader(new File(configLocation));
        SqlSessionFactory sessionfactory = new SqlSessionFactoryBuilder().build(reader);
        SqlSession sqlsession = sessionfactory.openSession();
    }

这个在熟悉不过了，这是构建sqlsession的大致流程；reader就不说了,首先看一下SqlSessionFactoryBuilder

/**
 *    Copyright 2009-2015 the original author or authors.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */
package org.apache.ibatis.session;

import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.util.Properties;

import org.apache.ibatis.builder.xml.XMLConfigBuilder;
import org.apache.ibatis.exceptions.ExceptionFactory;
import org.apache.ibatis.executor.ErrorContext;
import org.apache.ibatis.session.defaults.DefaultSqlSessionFactory;

/*
 * Builds {@link SqlSession} instances.
 *
 */
/**
 * @author Clinton Begin
 */
public class SqlSessionFactoryBuilder {

  public SqlSessionFactory build(Reader reader) {
    return build(reader, null, null);
  }

  public SqlSessionFactory build(Reader reader, String environment) {
    return build(reader, environment, null);
  }

  public SqlSessionFactory build(Reader reader, Properties properties) {
    return build(reader, null, properties);
  }

  public SqlSessionFactory build(Reader reader, String environment, Properties properties) {
    try {
      XMLConfigBuilder parser = new XMLConfigBuilder(reader, environment, properties);
      return build(parser.parse());
    } catch (Exception e) {
      throw ExceptionFactory.wrapException("Error building SqlSession.", e);
    } finally {
      ErrorContext.instance().reset();
      try {
        reader.close();
      } catch (IOException e) {
        // Intentionally ignore. Prefer previous error.
      }
    }
  }

  public SqlSessionFactory build(InputStream inputStream) {
    return build(inputStream, null, null);
  }

  public SqlSessionFactory build(InputStream inputStream, String environment) {
    return build(inputStream, environment, null);
  }

  public SqlSessionFactory build(InputStream inputStream, Properties properties) {
    return build(inputStream, null, properties);
  }

  public SqlSessionFactory build(InputStream inputStream, String environment, Properties properties) {
    try {
      XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties);
      return build(parser.parse());
    } catch (Exception e) {
      throw ExceptionFactory.wrapException("Error building SqlSession.", e);
    } finally {
      ErrorContext.instance().reset();
      try {
        inputStream.close();
      } catch (IOException e) {
        // Intentionally ignore. Prefer previous error.
      }
    }
  }
    
  public SqlSessionFactory build(Configuration config) {
    return new DefaultSqlSessionFactory(config);
  }

}

　　

这是sqlsessionfactorybuilder的源码，最重要的就是build方法，然后就是不同形式的参数，最终会有一个XMLConfigBuilder的实例对象，

调用他的parse方法会返回一个Configuration实例对象，Configration是整个mybatis配置的一个类里面包含了各种配置，然后调用build(Configuration config)方法返回一个SqlSessionFactory接口的一个实现类 DefaultSqlSessionFactory。返回一个DefaultSqlSessionFactory实例后就可以创建SQlsession对象了。sqlsession的创建过程还没看懂，慢慢更新吧。

这里面的XMLConfigBuilder 是一个Xml解析类，使用了jdk自带的XPath类库解析

解析后会把所有的配置放到上面到的configration实例中了，供其他类组件读取配置信息。 这里没贴全部源码，有兴趣的可以看看，感觉写的挺奇妙的。接下来会一个包一个包的读了