restopeer.java

JXTA技术手册 书上3.4.5章的源代码

                }

                // We received a message; extract the request
                try {
                    // Extract the HungryPipe pipe information
                    // to reply to the sender
                    ip = msg.getElement("HungryPeerPipe").getStream();

                    // Construct the associated pipe advertisement
                    // via the AdvertisementFactory
                    hungryPipe = (PipeAdvertisement)
                    AdvertisementFactory.newAdvertisement(mimeType, ip);

                    // Extract the sender name and fries size requested
                    // building a StructuredDocument
                    ip = msg.getElement("Request").getStream();
                    request = StructuredDocumentFactory.newStructuredDocument
                                    (mimeType, ip);

                    // Extract the fields from the structured Document
                    Enumeration enum = request.getChildren();

                    // Loop over all the elements of the document
                    while (enum.hasMoreElements()) {
                        el = (Element) enum.nextElement();
                        String attr = (String) el.getKey();
                        String value = (String) el.getValue();

                        // Extract the HungryPeer Requester Name
                        if (attr.equals("Name")) {
                            name = value;
                            continue;
                        }

                        // Extract the Fries  size requested
                        else if (attr.equals("Fries")) {
                            size = value;
                            continue;
                        }
                    }
                } catch (Exception e) {
                    continue; // Broken content; silently discard
                }

                System.out.println("Received Request from HungryPeer "
                               + name
                               + " for "
                               + size
                               + " Fries.");

                // The auction request is valid. We can
                // create the output pipe to send the response bid to
                // the HungryPeer requester
                try {
                    System.out.println(
                        "Attempting to create Output Pipe to HungryPeer " +
                        name);

                    // Create an output pipe connection to the HungryPeer
                    pipeOut = pipes.createOutputPipe(hungryPipe,
                                                     rtimeout);
                    // Check if we have a pipe
                    if (pipeOut == null) {
                        // Cannot conect the pipe
                        System.out.println("Could not find HungryPeer pipe");
                        continue;
                    }
                } catch (Exception e) {
                    // Pipe creation exception
                    System.out.println("HungryPeer may not be listening anymore");
                    continue;
                }

                // We have a pipe connection to the HungryPeer.
                // Now create the Bid Response document
                try {
                    // Construct the Response document
                    bid = StructuredDocumentFactory.newStructuredDocument(
                                     mimeType,
                                     "RestoNet:Bid");

                    // Set the Bid values (Brand, price, special)
                    // in the response document
                    el = bid.createElement("Brand", brand);
                    bid.appendChild(el);
                    el = bid.createElement("Price", friesPrice(size));
                    bid.appendChild(el);
                    el = bid.createElement("Specials", specials);
                    bid.appendChild(el);

                    // Create a new pipe message
                    msg = pipes.createMessage();

                    // Push the Bid offer in the message
                    msg.addElement(msg.newMessageElement(
                                   "Bid",mimeType, bid.getStream()));

                    // Send the message
                    pipeOut.send(msg);

                    // Close the output pipe connection
                    pipeOut.close();
                } catch (Exception ex) {
                    System.out.println(
                        "Error sending bid offer to HungryPeer " + name);
                    continue;
                }

                System.out.println("Sent Bid Offer to HungryPeer (" + name +
                       ") Fries price = "  + friesPrice(size) +
                       ", special = " + specials);
            } catch (Exception e) {
               System.out.println("Abort RestoPeer interrupted");
               return;
            }
        }
    }

    // Determine the price of the French fries depending on the size
    private String friesPrice(String size) {
        if (size.equals("small"))
              return "$1.50";
        if (size.equals("medium"))
              return "2.50";
        if (size.equals("large"))
              return "3.00";
        return "error";
    }

    // Create the resto pipe associated with this RestoPeer.
    // Discover first if a pipe advertisement exists, if
    // not create and publish it.
    private boolean createRestoPipe() {

        int count = 3;           // Discovery retry count
        Enumeration ae = null;   // Discovery response enumeration

        try {
            System.out.println(
                "Attempting to Discover the Restaurant RestoPipe");

            // Check if I have already published myself
            while (count-- > 0) {
                try {
                    // Check first locally if we have the advertisement cached
                    ae = disco.getLocalAdvertisements(DiscoveryService.ADV,
                                      "name", "RestoNet:RestoPipe:" + brand);

                    // If we found our pipe advertisement we are done
                    if (ae != null && ae.hasMoreElements())
                        break;

                    // We did not find the advertisement locally;
                    // send a remote request
                    disco.getRemoteAdvertisements(null,
                          DiscoveryService.ADV, "name",
                          "RestoNet:RestoPipe:" + brand, 1, null);

                    // Sleep to allow time for peers to respond to the
                    // discovery request
                    try {
                        Thread.sleep(timeout);
                    } catch (InterruptedException e) {}
                } catch (IOException e) {
                    // Found nothing! Move on
                }
            }

            if (ae == null || !ae.hasMoreElements()) {
                // We did not find the pipe advertisement, so create one
                System.out.println(
                    "Could not find the Restaurant Pipe Advertisement");

                // Create a pipe advertisement for our RestoPeer
                myAdv = (PipeAdvertisement)
                    AdvertisementFactory.newAdvertisement(
                        PipeAdvertisement.getAdvertisementType());

                // Assign a unique ID to the pipe
                myAdv.setPipeID(
                        IDFactory.newPipeID(restoNet.getPeerGroupID() ));

                // The symbolic name of the pipe is built from
                // the brand name of RestoPeer;  each RestoPeer
                // must therefore have a unique name.
                myAdv.setName("RestoNet:RestoPipe:" + brand);

                // Set the type of the pipe to be unidirectional
                myAdv.setType(PipeService.UnicastType);

                // We have the advertisement; publish it
                // into our local cache and to the RestoNet PeerGroup.
                // We use the default lifetime and the default
                // expiration time for remote publishing
                disco.publish(myAdv, DiscoveryService.ADV,
                              PeerGroup.DEFAULT_LIFETIME,
                              PeerGroup.DEFAULT_EXPIRATION);
                disco.remotePublish(myAdv, DiscoveryService.ADV,
                              PeerGroup.DEFAULT_EXPIRATION);

                System.out.println(
                    "Created the Restaurant Pipe Advertisement");
            } else {
                // We found an existing pipe advertisement
                myAdv = (PipeAdvertisement) ae.nextElement();
                System.out.println("Found Restaurant Pipe Advertisement");
            }

            // Create my input pipe to listen for hungry peers
            // requests
            pipeIn = pipes.createInputPipe(myAdv);
        } catch (Exception e) {
            System.out.println("Could not initialize the Restaurant pipe");
            return false;
        }
        return true;
    }

    private PeerGroupID mkGroupID() throws Exception {
        return (PeerGroupID) IDFactory.fromURL(
             new URL("urn", "", groupURL));
    }
}