myBatis源码学习之SqlSessionFactoryBuilder

SqlSessionFactoryBuilder通过类名就可以看出这个类的主要作用就是创建一个SqlSessionFactory，通过输入mybatis配置文件的字节流或者字符流，生成XMLConfigBuilder，XMLConfigBuilder创建一个Configuration，Configuration这个类中包含了mybatis的配置的一切信息，mybatis进行的所有操作都需要根据Configuration中的信息来进行。

SqlSessionFactoryBuilder源码及注释：

/*
 * Builds {@link SqlSession} instances.
 *
 */
/**
 * @author Clinton Begin
 */
//通过读入配置文件，最终获得一个sqlSessionFactory
public class SqlSessionFactoryBuilder {
  //已字符输入流引入配置文件
  public SqlSessionFactory build(Reader reader) {
    return build(reader, null, null);
  }
  //environment是数据源环境
  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 {
	  //解析myBatis配置文件，以字符流的方式
      XMLConfigBuilder parser = new XMLConfigBuilder(reader, environment, properties);
      return build(parser.parse());//获得SqlSessionFactory
    } 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.
      }
    }
  }
  //以字节输入流传入配置信息
  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 {
		//解析myBatis配置文件，以字节流的方式
      XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties);
      return build(parser.parse());//获得SqlSessionFactory
    } 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) {
	//获得sqlsessionFactory工厂，再从工厂中获得sqlsession
    return new DefaultSqlSessionFactory(config);
  }

}

mybatis执行流程图：