groupmanager.java~

Java p2p程序设计2002年版

package com.sams.jxta.groups;

import net.jxta.credential.AuthenticationCredential;
import net.jxta.credential.Credential;
import net.jxta.discovery.DiscoveryService;
import net.jxta.document.Advertisement;
import net.jxta.document.AdvertisementFactory;
import net.jxta.document.StructuredDocument;
import net.jxta.document.StructuredTextDocument;
import net.jxta.exception.PeerGroupException;
import net.jxta.exception.ProtocolNotSupportedException;
import net.jxta.impl.id.UUID.UUIDFactory;
import net.jxta.impl.protocol.PeerGroupAdv;
import net.jxta.peergroup.PeerGroupID;
import net.jxta.peergroup.PeerGroupFactory;
import net.jxta.impl.peergroup.StdPeerGroupParamAdv;
import net.jxta.membership.Authenticator;
import net.jxta.membership.MembershipService;
import net.jxta.peergroup.PeerGroup;
import net.jxta.protocol.ModuleImplAdvertisement;
import net.jxta.protocol.PeerGroupAdvertisement;

import java.util.Enumeration;
import java.util.Hashtable;

/**
 * This class can be used to create a new group with a pluggable 
 * Membership service.It provides simple APIs for Apply,Join and Resign
 * functionalities.
 */

public class GroupManager {

    private static final org.apache.log4j.Category LOG = 
        org.apache.log4j.Category.getInstance(GroupManager.class.getName());
    protected DiscoveryService disco;
    // The parent group of the current peer group
    protected PeerGroup parent;
    // Net peer for creating advertisements.
    protected PeerGroup netPeerGroup;
    // The current peer group
    protected PeerGroup activeGroup;
    // Any module(like a peer group) that is loaded by the parent group,must 
    // be compatible with the parent.Compatibility is checked by comparision 
    // with the stdCompactStatement 
    public StructuredTextDocument stdCompatStatement = // ??? Taken from StdPeerGroup
                mkCS();
    // An identifier to the implementation used // ??? Is it so ?
    public String stdUri = "http://www.jxta.org/download/jxta.jar";// ??? Taken from StdPeerGroup
    // The provider of the implementation // ??? Is it so ?
    public String stdProvider = "sun.com";// ??? Taken from StdPeerGroup

    // The mime type of all documents used in this example
    public static final String DOCUMENT_MIME_TYPE="text";
    // The base type of all documents
    public static final String DOCUMENT_BASE_TYPE="xml";
    // This is the root element documents created
    public static final String DOCUMENT_ROOT_ELEMENT="Comp";    
    // Key ??? What is this used for ?
    private static final String KEY="Efmt";    
    // Value ??? What is this used for ?
    private static final String VALUE="JDK1.4";
    // Key used to represent the binding
    private static final String BINDING_KEY="Bind";
    // Value of the binding key.It represents the binding 
    // of JXTA that we use.
    private static final String BINDING_VALUE="V1.0 Ref Impl";
   
    /** 
     * The constructor of the Group Manger.Initially 
     * the parent group is the also the active group.
     */
     
    public GroupManager(PeerGroup netPeerGroup, PeerGroup parent) {
   
        this.disco  = parent.getDiscoveryService();
        this.parent = parent;
        this.activeGroup = parent;
        this.netPeerGroup = netPeerGroup;
        if (netPeerGroup ==  null){
            System.out.println("netPeerGroup :"+netPeerGroup+" - aborting");
            throw new NullPointerException("netPeerGroup :"+netPeerGroup+" - aborting");
            
        }
   }
    
    /* 
     *   Method to add a new peer group and publish it.The 
     *   groupMemebershipClassName is the fully qualified class 
     *   name of the mermbership service class.
     *
     */
     
    public PeerGroup addGroup(String groupName,String groupMembershipClassName,
                              String groupDescription,
                              ModuleImplAdvertisement advertisement,
                              boolean conditional){
System.out.println("GroupManager.addGroup Successfully created SecurityDemoGroup");
        // The first thing we do is to see if a group already exists by this name.
        // If so we get the Group ID of the group. Then depending on the unconditional
        // flag we proceed.
        // If it is an conditional add ,we create a new group only if no other group
        // with the same name already exists otherwise we throw an exception.
        // If it is an unconditional add , we always create  a group.If the user had previously
        // created the group , we use the Old group ID . 
        PeerGroupID oldPeerGroupID = alreadyExists(groupName);
        if(oldPeerGroupID != null && conditional==true)
            throw new GroupManagerException("A Group by this name already exists with id :"
                                             +oldPeerGroupID);
        
        // If no Advertisement is provided, we create a fresh advertisement.
        if (advertisement == null){
            LOG.debug("Creating a new Advertisement");
            // We use the existing advertisement of the standard peer group
            // and add our service along with the other standard services 
            try{
                // This is used as a base to create the new advertisement upon    
                System.out.println("netPeerGroup :"+netPeerGroup);
                advertisement = netPeerGroup.getAllPurposePeerGroupImplAdvertisement();
                //advertisement = parent.getAllPurposePeerGroupImplAdvertisement();//<< Did not work in current platform
                StructuredDocument paramDoc = advertisement.getParam();
                System.out.println("StructuredDocument paramDoc:"+paramDoc);
                // The Param document used to make the StandradPeerGroup Advertisement
                StdPeerGroupParamAdv paramAdv = new StdPeerGroupParamAdv(paramDoc);
                // List of all the available standard services
                Hashtable services = paramAdv.getServices();
                // Make a ModuleImplAdvertisemnet for the membership service
                ModuleImplAdvertisement moduleAdv = 
                    mkImplAdvBuiltin(PeerGroup.refMembershipSpecID,groupMembershipClassName,
                                     groupDescription);
                // Add this service along the other standard services            
                services.put(PeerGroup.membershipClassID, moduleAdv);
                paramAdv.setServices(services);
                advertisement.setParam((net.jxta.document.TextElement)paramAdv.getDocument(
                              new net.jxta.document.MimeMediaType(DOCUMENT_MIME_TYPE,
                                                                  DOCUMENT_BASE_TYPE)));
            }catch(PeerGroupException peerGroupException){
                peerGroupException.printStackTrace();
                System.exit(-1);
                LOG.error("Error in creating Advertisement",peerGroupException);
                throw new GroupManagerException(peerGroupException.getMessage());
            }catch(Exception genericException){
                genericException.printStackTrace();
                LOG.error("Error in creating Advertisement",genericException);
                System.exit(-1);
                throw new GroupManagerException(genericException.getMessage());
            }
        }
        LOG.debug("Successfullt created ADVERTISEMENT");  
        
        // initialize but to no start the application
        // this is done by the join command
        LOG.debug("Creating the Peer Group");        
        PeerGroup peerGroup = null;
        try {
            // create a PeerGroup ID
            PeerGroupID peerGroupID = null;
            if(oldPeerGroupID != null){
                peerGroupID = oldPeerGroupID;
            }else{
                peerGroupID = new net.jxta.impl.id.UUID.PeerGroupID(UUIDFactory.newUUID());
            }
            // create the PeerGroup
            peerGroup = parent.newGroup(peerGroupID, advertisement, groupName, groupDescription);////
            // initialize the peergroup
            peerGroup.init(this.parent,peerGroupID, advertisement);
        } catch (PeerGroupException peerGroupException) {
            peerGroupException.printStackTrace();
            LOG.error("Unable to create a peer group !",peerGroupException);
            throw new GroupManagerException(peerGroupException.getMessage());
        }
        // For debug purposes, print advertisement to console
        //com.sams.jxta.Util.printAdvertismentDoc(advertisement);
        // Try to publish the advertisement
        LOG.debug("Trying to publish the advertisement");
        publish(peerGroup, advertisement/*original advertisement???*/);
        LOG.debug("Peer Group Advertisement successfully published");
        return peerGroup;
  
   }

    /** 
     * Will check if a peer group with the same name exists on this peer
     */

    public PeerGroupID alreadyExists(String name){
    
        DiscoveryService discovery = parent.getDiscoveryService();
        Enumeration enumeration =null;
        try{
            enumeration =
                discovery.getLocalAdvertisements(discovery.GROUP, "Name",name);
        } catch(java.io.IOException ioException) {
            LOG.debug("Error in getting local advertisements ");
            return null;
        }
        // If the group already exists either the  enumeration is null
        // or it does not contain any data 
        
        if(enumeration != null && enumeration.hasMoreElements())
            return ((PeerGroupAdv)enumeration.nextElement()).getPeerGroupID();
        else
            return null; 
    }

    // Tries to publish the newly created peer group  
    // ??? Why do we need the original Advertisement ?
    private void publish(PeerGroup child,Advertisement pgAdv
                               //PeerGroupAdvertisement origAdv
                               ) {
      System.out.println("Publishing group");
      //get the Discovery for this group
      //Publish the New Peer in its group discovery
      
      DiscoveryService discovery;
      try {
         discovery = parent.getDiscoveryService();
         discovery.publish(pgAdv, DiscoveryService.GROUP);
         // let's publish the peer adv
         //if (origAdv != null){//?????? Not sure what this does
            // we could check if it is indeed ours
            // but it does not hurt to publish it any way
         //   discovery = child.getDiscoveryService();
         //   discovery.publish(origAdv, DiscoveryService.GROUP);