clientdispatcher.java

webwork source

/*
 * WebWork, Web Application Framework
 *
 * Distributable under Apache license.
 * See terms of license at opensource.org
 */
package webwork.action.client;

import webwork.action.Action;

import java.io.*;
import java.net.URL;
import java.net.URLConnection;
import java.applet.Applet;

/**
 * The ClientDispatcher is used by remote clients to execute actions
 * on a server running WebWork.
 *
 * @author Rickard 謆erg ([e-mail])
 */
public class ClientDispatcher
{
   // Attributes ----------------------------------------------------
   String host;

   // Static --------------------------------------------------------
   /**
    * Standard dispatcher servlet URL
    */
   public static final String DISPATCHER = "/servlet/dispatch";

   // Constructors --------------------------------------------------
   /**
    * Create a new dispatcher with an applet providing the URL.
    *
    * The servlet needs to be deployed with the name "dispatch".
    */
   public ClientDispatcher(Applet anApplet, String context)
      throws java.net.MalformedURLException
   {
      this( new URL(anApplet.getDocumentBase(),
            context+DISPATCHER).toExternalForm());
   }

   /**
    * Create a new dispatcher.
    *
    * @param aHost The URL of the servlet handler
    */
   public ClientDispatcher(String aHost)
   {
      host = aHost;
   }
   // Public --------------------------------------------------------
   public String getHost()
   {
      return host;
   }

   /**
    * Execute the action on the server.
    *
    * @return the result of the execution, including the action itself
    */
   public ActionResult execute(Action anAction)
      throws Exception
   {
      URL webworkHostServlet = new URL(host);
      URLConnection webworkHostServletConnection = webworkHostServlet.openConnection();

      // Inform the connection that we will send output and accept input
      webworkHostServletConnection.setDoInput(true);
      webworkHostServletConnection.setDoOutput(true);

      // Don't use a cached version of URL connection.
      webworkHostServletConnection.setUseCaches (false);

      // Specify the content type that we will send binary data
      webworkHostServletConnection.setRequestProperty ("Content-Type", "application/octet-stream");

      // Send the action to the servlet using serialization
      ObjectOutputStream out = createObjectOutputStream(new BufferedOutputStream(webworkHostServletConnection.getOutputStream()));

      // Serialize the action
      out.writeObject(anAction);
      out.flush();

      // Get the result
      ObjectInputStream in = createObjectInputStream(new BufferedInputStream(webworkHostServletConnection.getInputStream()));

      ActionResult actionResult = (ActionResult)in.readObject();

      out.close();
      in.close();

      if (actionResult.getException() != null)
         throw actionResult.getException();

      return actionResult;
   }

   // Protected -----------------------------------------------------
   /**
    * Create an object input stream that wraps the URL connection stream.
    *
    * This method can be overriden in order to create custom streams.
    *
    * @param in the underlying stream. It is buffered
    * @return an object input stream
    * @throws IOException
    */
   protected ObjectInputStream createObjectInputStream(InputStream in)
      throws IOException
   {
      return new ObjectInputStream(in);
   }

   /**
    * Create an object input stream that wraps the URL connection stream.
    *
    * This method can be overriden in order to create custom streams.
    *
    * @param out The OutputStream to wrap
    * @return an ObjectOutputStream wrapping the specified OutputStream
    * @throws IOException
    */
   protected ObjectOutputStream createObjectOutputStream(OutputStream out)
      throws IOException
   {
      return new ObjectOutputStream(out);
   }
}