Thrift源码解析--transport

这一层主要是用于实现网络通信，现在都是基于Tcp/Ip，而Tcp/Ip协议栈由socket来实现，换句话说就是现在网络通信服务底层大都是通过socket实现的，在thrift源码中，就是将socket包装成各种transport来使用。

TTransport:这是一个基类，并且是一个抽象类。

TIOStreamTransport继承TTransport类，是最常用的base transport, It takes an InputStream and an OutputStream and uses those to perform all transport operations.主要是由inputStream和OutputStream进行读写操作，主要有open,close,read,write,flush等方法。代码如下：

public class TIOStreamTransport extends TTransport {

  private static final Logger LOGGER = LoggerFactory.getLogger(TIOStreamTransport.class.getName());

  /** Underlying inputStream */
  protected InputStream inputStream_ = null;

  /** Underlying outputStream */
  protected OutputStream outputStream_ = null;

  /**
   * Subclasses can invoke the default constructor and then assign the input
   * streams in the open method.
   */
  protected TIOStreamTransport() {}

  /**
   * Input stream constructor.
   *
   * @param is Input stream to read from
   */
  public TIOStreamTransport(InputStream is) {
    inputStream_ = is;
  }

  /**
   * Output stream constructor.
   *
   * @param os Output stream to read from
   */
  public TIOStreamTransport(OutputStream os) {
    outputStream_ = os;
  }

  /**
   * Two-way stream constructor.
   *
   * @param is Input stream to read from
   * @param os Output stream to read from
   */
  public TIOStreamTransport(InputStream is, OutputStream os) {
    inputStream_ = is;
    outputStream_ = os;
  }

  /**
   * The streams must already be open at construction time, so this should
   * always return true.
   *
   * @return true
   */
  public boolean isOpen() {
    return true;
  }

  /**
   * The streams must already be open. This method does nothing.
   */
  public void open() throws TTransportException {}

  /**
   * Closes both the input and output streams.
   */
  public void close() {
    if (inputStream_ != null) {
      try {
        inputStream_.close();
      } catch (IOException iox) {
        LOGGER.warn("Error closing input stream.", iox);
      }
      inputStream_ = null;
    }
    if (outputStream_ != null) {
      try {
        outputStream_.close();
      } catch (IOException iox) {
        LOGGER.warn("Error closing output stream.", iox);
      }
      outputStream_ = null;
    }
  }

  /**
   * Reads from the underlying input stream if not null.
   */
  public int read(byte[] buf, int off, int len) throws TTransportException {
    if (inputStream_ == null) {
      throw new TTransportException(TTransportException.NOT_OPEN, "Cannot read from null inputStream");
    }
    int bytesRead;
    try {
      bytesRead = inputStream_.read(buf, off, len);
    } catch (IOException iox) {
      throw new TTransportException(TTransportException.UNKNOWN, iox);
    }
    if (bytesRead < 0) {
      throw new TTransportException(TTransportException.END_OF_FILE);
    }
    return bytesRead;
  }

  /**
   * Writes to the underlying output stream if not null.
   */
  public void write(byte[] buf, int off, int len) throws TTransportException {
    if (outputStream_ == null) {
      throw new TTransportException(TTransportException.NOT_OPEN, "Cannot write to null outputStream");
    }
    try {
      outputStream_.write(buf, off, len);
    } catch (IOException iox) {
      throw new TTransportException(TTransportException.UNKNOWN, iox);
    }
  }

  /**
   * Flushes the underlying output stream if not null.
   */
  public void flush() throws TTransportException {
    if (outputStream_ == null) {
      throw new TTransportException(TTransportException.NOT_OPEN, "Cannot flush null outputStream");
    }
    try {
      outputStream_.flush();
    } catch (IOException iox) {
      throw new TTransportException(TTransportException.UNKNOWN, iox);
    }
  }
}

TSocket继承了TIOStreamTransport类，封装了Socket接口，含有host,port,socket,timeout几个私有变量，并且有open,isOpen,initSocket,getSocket,setTimeout方法，由于继承自TIOStreamTransport,因此父类的读写方法都可以使用，也就是说TSocket的通信根本还是使用的输入输出流。

 TserverSocket继承自TserverTransport,

TNoblockingServerTransport继承自TserverTransport,

TNoblockingServerSocket继承自TNoblockingServerTransport

图中的XoaServerTransport暂时忽略（公司内部xoa框架使用)

以上是用于服务端，而客户端则如右下图所示，不再赘述。