hession

hession 远程调用框架，
粗略看了下源码，大致是一个客户端 通过代理模式创建代理对象，当代理对象去调用服务端的方法的时候 才去请求服务。（通过http协议post二进制数据过去） 
服务端通过发送过来的方法名字和参数（反序列化） 调用服务端的方法返回。

proxy+http+Serialization(代理模式，http请求，序列化)。

1.当代理对象去调用服务端的方法的时候 才去请求服务  过程

com.caucho.hessian.client.HessianProxy

 /**
   * Sends the HTTP request to the Hessian connection.
   */
  protected HessianConnection sendRequest(String methodName, Object []args)
    throws IOException
  {
    HessianConnection conn = null;
    
    conn = _factory.getConnectionFactory().open(_url);
    boolean isValid = false;

    try {
      addRequestHeaders(conn);

      OutputStream os = null;

      try {
        os = conn.getOutputStream();
      } catch (Exception e) {
        throw new HessianRuntimeException(e);
      }

      if (log.isLoggable(Level.FINEST)) {
        PrintWriter dbg = new PrintWriter(new LogWriter(log));
        HessianDebugOutputStream dOs = new HessianDebugOutputStream(os, dbg);
        dOs.startTop2();
        os = dOs;
      }
      
      AbstractHessianOutput out = _factory.getHessianOutput(os);

      out.call(methodName, args);
      out.flush();

      conn.sendRequest();

      isValid = true;

      return conn;
    } finally {
      if (! isValid && conn != null)
        conn.destroy();
    }
  }

通过java.net.URLConnection发生http post请求，连接获取过程

com.caucho.hessian.client.HessianURLConnectionFactory

 /**
   * Opens a new or recycled connection to the HTTP server.
   */
  public HessianConnection open(URL url)
    throws IOException
  {
    if (log.isLoggable(Level.FINER))
      log.finer(this + " open(" + url + ")");

    URLConnection conn = url.openConnection();

    // HttpURLConnection httpConn = (HttpURLConnection) conn;
    // httpConn.setRequestMethod("POST");
    // conn.setDoInput(true);

    long connectTimeout = _proxyFactory.getConnectTimeout();

    if (connectTimeout >= 0)
      conn.setConnectTimeout((int) connectTimeout);

    conn.setDoOutput(true);

    long readTimeout = _proxyFactory.getReadTimeout();

    if (readTimeout > 0) {
      try {
        conn.setReadTimeout((int) readTimeout);
      } catch (Throwable e) {
      }
    }

    /*
    // Used chunked mode when available, i.e. JDK 1.5.
    if (_proxyFactory.isChunkedPost() && conn instanceof HttpURLConnection) {
      try {
        HttpURLConnection httpConn = (HttpURLConnection) conn;

        httpConn.setChunkedStreamingMode(8 * 1024);
      } catch (Throwable e) {
      }
    }
    */
    
    return new HessianURLConnection(url, conn);
  }

2.hession服务端

开发时，spring-web包提供org.springframework.remoting.caucho.HessianServiceExporter类。

<bean name="/**Service" class="org.springframework.remoting.caucho.HessianServiceExporter" depends-on="**Service">
<property name="service" ref="**Service" />
<property name="serviceInterface" value="**Service" />
</bean>

服务端接收请求过程

请求通过dispatcherServlet类的doDispatch方法。

    /**
     * Process the actual dispatching to the handler.
     * <p>The handler will be obtained by applying the servlet's HandlerMappings in order.
     * The HandlerAdapter will be obtained by querying the servlet's installed HandlerAdapters
     * to find the first that supports the handler class.
     * <p>All HTTP methods are handled by this method. It's up to HandlerAdapters or handlers
     * themselves to decide which methods are acceptable.
     * @param request current HTTP request
     * @param response current HTTP response
     * @throws Exception in case of any kind of processing failure
     */
    protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
        HttpServletRequest processedRequest = request;
        HandlerExecutionChain mappedHandler = null;
        boolean multipartRequestParsed = false;

        WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);

        try {
            ModelAndView mv = null;
            Exception dispatchException = null;

            try {
                processedRequest = checkMultipart(request);
                multipartRequestParsed = (processedRequest != request);

                // Determine handler for the current request.
                mappedHandler = getHandler(processedRequest);
                if (mappedHandler == null || mappedHandler.getHandler() == null) {
                    noHandlerFound(processedRequest, response);
                    return;
                }

                // Determine handler adapter for the current request.
                HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

                // Process last-modified header, if supported by the handler.
                String method = request.getMethod();
                boolean isGet = "GET".equals(method);
                if (isGet || "HEAD".equals(method)) {
                    long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
                    if (logger.isDebugEnabled()) {
                        logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified);
                    }
                    if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
                        return;
                    }
                }

                if (!mappedHandler.applyPreHandle(processedRequest, response)) {
                    return;
                }

                // Actually invoke the handler.
                mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

                if (asyncManager.isConcurrentHandlingStarted()) {
                    return;
                }

                applyDefaultViewName(processedRequest, mv);
                mappedHandler.applyPostHandle(processedRequest, response, mv);
            }
            catch (Exception ex) {
                dispatchException = ex;
            }
            processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
        }
        catch (Exception ex) {
            triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
        }
        catch (Error err) {
            triggerAfterCompletionWithError(processedRequest, response, mappedHandler, err);
        }
        finally {
            if (asyncManager.isConcurrentHandlingStarted()) {
                // Instead of postHandle and afterCompletion
                if (mappedHandler != null) {
                    mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
                }
            }
            else {
                // Clean up any resources used by a multipart request.
                if (multipartRequestParsed) {
                    cleanupMultipart(processedRequest);
                }
            }
        }
    }

getHandlerAdapter

    /**
     * Return the HandlerAdapter for this handler object.
     * @param handler the handler object to find an adapter for
     * @throws ServletException if no HandlerAdapter can be found for the handler. This is a fatal error.
     */
    protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException {
        for (HandlerAdapter ha : this.handlerAdapters) {
            if (logger.isTraceEnabled()) {
                logger.trace("Testing handler adapter [" + ha + "]");
            }
            if (ha.supports(handler)) {
                return ha;
            }
        }
        throw new ServletException("No adapter for handler [" + handler +
                "]: The DispatcherServlet configuration needs to include a HandlerAdapter that supports this handler");
    }

通过下图可以知道有3个handleAdapter

我们看下HttpRequestHandlerAdapter这个类

public class HttpRequestHandlerAdapter implements HandlerAdapter {

    @Override
    public boolean supports(Object handler) {
        return (handler instanceof HttpRequestHandler);
    }

    @Override
    public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
            throws Exception {

        ((HttpRequestHandler) handler).handleRequest(request, response);
        return null;
    }

    @Override
    public long getLastModified(HttpServletRequest request, Object handler) {
        if (handler instanceof LastModified) {
            return ((LastModified) handler).getLastModified(request);
        }
        return -1L;
    }

}

HessianServiceExporter类实现了HttpRequestHandler接口。

所有这里返回HttpRequestHandlerAdapter。

最后((HttpRequestHandler) handler).handleRequest(request, response) 去处理请求。