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。