Code Details

This section contains the code for the P2P Dashboard program. Three Java classes make up the P2P Dashboard sample program: P2PDashboard, the main class; PeerDiscovery, a class that handles local/remote peer discovery management; and GroupDiscovery, a class that handles local/remote group discovery management.

Details of the P2PDashboard Class

P2PDashboard.java is the main class that encapsulates all graphical user interface elements, such as the window frame, command buttons, scroll pane, text fields, radio buttons, tree structure, and button groups for the Dashboard, and it directly interfaces with the JXTA platform.

P2Pdashboard.java employs the following methods:

• main() to run the program

• P2PDashboard() to create the frame for the Dashboard GUI

• initializeGUIComponents() to set up GUI objects and their properties

• configureGroupEvents() to handle group GUI object events

• configurePeerEvents() to handle peer GUI object events

• exitForm(WindowEvent) to exit the application

• handleError(String, String, Exception, boolean) for error handling

• checkAddRules(String) for group validation

P2PDashboard utilizes the following JXTA methods:

• initializeNetPeerGroup() to initialize the default NetPeerGroup to which a local peer belongs

• initializeDiscovery() to initialize the peer and group discovery services for handling local and remote discovery events and messages

• addPeer(String) to create a peer and publish it locally and remotely

• removeAdvertisement (String,boolean) to remove a peer's credentials from the local cache

• addGroup(String) to create a new group and publish it locally and remotely

Listing 19.1 presents the code for P2PDashboard.java.

Listing 19.1 P2PDashboard.java

 import java.awt.Container; import java.awt.Insets; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.ItemEvent; import java.awt.event.ItemListener; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import java.io.IOException; import java.lang.String; import java.util.Enumeration; import java.util.Hashtable; import java.util.Vector; import javax.swing.ButtonGroup; import javax.swing.JButton; import javax.swing.JCheckBox; import javax.swing.JFrame; import javax.swing.JList; import javax.swing.JOptionPane; import javax.swing.JRadioButton; import javax.swing.JScrollPane; import javax.swing.JTextField; import javax.swing.ListSelectionModel; import javax.swing.DefaultListSelectionModel; import javax.swing.border.TitledBorder; import javax.swing.event.ListSelectionListener; import javax.swing.event.ListSelectionEvent; import net.jxta.credential.AuthenticationCredential; import net.jxta.document.StructuredDocument; import net.jxta.document.MimeMediaType; import net.jxta.discovery.DiscoveryService; import net.jxta.exception.PeerGroupException; import net.jxta.membership.Authenticator; import net.jxta.membership.MembershipService; import net.jxta.peergroup.PeerGroup; import net.jxta.peergroup.PeerGroupFactory; import net.jxta.protocol.ModuleImplAdvertisement; import net.jxta.protocol.PeerGroupAdvertisement; import net.jxta.protocol.PeerAdvertisement; import net.jxta.impl.protocol.PeerGroupAdv; import net.jxta.impl.protocol.PeerAdv; import net.jxta.impl.id.UUID.PeerID; import net.jxta.impl.id.UUID.PeerGroupID; /*   P2P Dashboard application  */ public class P2PDashboard extends JFrame {   // frame reference for JOptionPane message dialogs   private JFrame frame;   // group section   private JScrollPane groupScrollPane;   private JList groupList;   private Hashtable groupHT;   private JTextField groupAddTextField;   private JButton groupAddButton;   private JButton groupFlushButton;   private JButton groupRemoveButton;   private JRadioButton groupLocalRadioButton;   private JRadioButton groupRemoteRadioButton;   private ButtonGroup groupDiscoveryButtonGroup;   private JButton groupDiscoveryButton;   // peer section   private JScrollPane peerScrollPane;   private JList peerList;   private JTextField peerAddTextField;   private JButton peerAddButton;   private JButton peerFlushButton;   private JCheckBox peerCheckBox;   private JButton peerRemoveButton;   private JRadioButton peerLocalRadioButton;   private JRadioButton peerRemoteRadioButton;   private ButtonGroup peerDiscoveryButtonGroup;   private JButton peerDiscoveryButton;   private boolean displayPeerGroups;   // Default NetPeerGroup and discovery service   private static PeerGroup netPeerGroup;   private DiscoveryService discovery;   private String defaultGroupName;   private String defaultPeerName;   // peer and group discovery event handlers   private PeerDiscovery peerDiscovery;   private GroupDiscovery groupDiscovery;   /*********************/   /* Dashboard Methods */   /*********************/   /*    *Command line arguments    */   public static void main(String args[])   {     P2PDashboard p2p = new P2PDashboard();     p2p.show();     // setup localPeer in NetPeerGroup     p2p.initializeNetPeerGroup();     // prepare peer and group discovery services     p2p.initializeDiscovery();   }   /*    *Create a new P2PDashboard frame.    */   public P2PDashboard()   {     frame = this;     // group     groupScrollPane = new JScrollPane();     groupList = new JList(new SortedListModel());     groupHT = new Hashtable();     groupAddTextField = new JTextField();     groupAddButton = new JButton();     groupFlushButton = new JButton();     groupRemoveButton = new JButton();     groupLocalRadioButton = new JRadioButton();     groupRemoteRadioButton = new JRadioButton();     groupDiscoveryButtonGroup = new ButtonGroup();     groupDiscoveryButton = new JButton();     // peer     peerScrollPane = new JScrollPane();     peerList = new JList(new SortedListModel());     peerAddTextField = new JTextField();     peerAddButton = new JButton();     peerFlushButton = new JButton();     peerCheckBox = new JCheckBox();     peerRemoveButton = new JButton();     peerLocalRadioButton = new JRadioButton();     peerRemoteRadioButton = new JRadioButton();     peerDiscoveryButtonGroup = new ButtonGroup();     peerDiscoveryButton = new JButton();     displayPeerGroups = false;     initializeGUIComponents();     configureGroupEvents();     configurePeerEvents();   }   /*    *P2PDashboard uses this to setup GUI objects and    *their properties.    */   private void initializeGUIComponents()   {     Container contentPane = getContentPane();     Insets insets = contentPane.getInsets();     contentPane.setLayout(null);     // group section     groupScrollPane.setViewportBorder (new TitledBorder("Groups"));     groupScrollPane.setViewportView(groupList);     contentPane.add(groupScrollPane);     groupScrollPane.setBounds(10+insets.left, 10+insets.top, 250, 230);     groupAddTextField.setToolTipText("Add a new group");     contentPane.add(groupAddTextField);     groupAddTextField.setBounds(10+insets.left, 250+insets.top, 140, 20);     groupAddButton.setText("Add");     groupAddButton.setToolTipText("Add a new group");     contentPane.add(groupAddButton);     groupAddButton.setBounds(170+insets.left, 250+insets.top, 90, 20);     groupFlushButton.setText("Flush");     groupFlushButton.setToolTipText ("Flush local group cache");     contentPane.add(groupFlushButton);     groupFlushButton.setBounds(10+insets.left, 280+insets.top, 90, 20);     groupRemoveButton.setText("Remove");     groupRemoveButton.setToolTipText("Remove a group");     contentPane.add(groupRemoveButton);     groupRemoveButton.setBounds(170+insets.left, 280+insets.top, 90, 20);     groupLocalRadioButton.setSelected(true);     groupLocalRadioButton.setText("Local");     groupLocalRadioButton.setToolTipText ("Search for local groups");     contentPane.add(groupLocalRadioButton);     groupLocalRadioButton.setBounds(10+insets.left, 310+insets.top, 60, 20);     groupRemoteRadioButton.setText("Remote");     groupRemoteRadioButton.setToolTipText ("Search for remote groups");     contentPane.add(groupRemoteRadioButton);     groupRemoteRadioButton.setBounds(90+insets.left, 310+insets.top, 70, 20);     groupDiscoveryButtonGroup.add(groupLocalRadioButton);     groupDiscoveryButtonGroup.add(groupRemoteRadioButton);     groupDiscoveryButton.setText("Discover");     groupDiscoveryButton.setToolTipText("Find groups");     contentPane.add(groupDiscoveryButton);     groupDiscoveryButton.setBounds(170+insets.left, 310+insets.top, 90, 20);     // peer section     peerScrollPane.setViewportBorder (new TitledBorder("Peers"));     peerScrollPane.setViewportView(peerList);     contentPane.add(peerScrollPane);     peerScrollPane.setBounds(290+insets.left, 10+insets.top, 250, 230);     peerAddTextField.setToolTipText("Add a new peer");     contentPane.add(peerAddTextField);     peerAddTextField.setBounds(290+insets.left, 250+insets.top, 140, 20);     peerAddButton.setText("Add");     peerAddButton.setToolTipText("Add a new peer");     contentPane.add(peerAddButton);     peerAddButton.setBounds(450+insets.left, 250+insets.top, 90, 20);     peerFlushButton.setText("Flush");     peerFlushButton.setToolTipText ("Flush local peer cache");     contentPane.add(peerFlushButton);     peerFlushButton.setBounds(290+insets.left, 280+insets.top, 90, 20);     peerCheckBox.setSelected(false);     peerCheckBox.setText("Groups");     peerCheckBox.setToolTipText ("Display groups peer is in.");     contentPane.add(peerCheckBox);     peerCheckBox.setBounds(386+insets.left, 280+insets.top, 60, 20);     peerRemoveButton.setText("Remove");     peerRemoveButton.setToolTipText("Remove a peer");     contentPane.add(peerRemoveButton);     peerRemoveButton.setBounds(450+insets.left, 280+insets.top, 90, 20);     peerLocalRadioButton.setSelected(true);     peerLocalRadioButton.setText("Local");     peerLocalRadioButton.setToolTipText ("Search for local peers");     contentPane.add(peerLocalRadioButton);     peerLocalRadioButton.setBounds(290+insets.left, 310+insets.top, 60, 20);     peerRemoteRadioButton.setText("Remote");     peerRemoteRadioButton.setToolTipText ("Search for remote peers");     contentPane.add(peerRemoteRadioButton);     peerRemoteRadioButton.setBounds(370+insets.left, 310+insets.top, 70, 20);     peerDiscoveryButtonGroup.add(peerLocalRadioButton);     peerDiscoveryButtonGroup.add(peerRemoteRadioButton);     peerDiscoveryButton.setText("Discover");     peerDiscoveryButton.setToolTipText("Find peers");     contentPane.add(peerDiscoveryButton);     peerDiscoveryButton.setBounds(450+insets.left, 310+insets.top, 90, 20);     pack();     setTitle("P2P Dashboard");     setSize(558, 365);     setResizable(false);     // JFrame event     addWindowListener(new WindowAdapter() {       public void windowClosing(WindowEvent evt)       {         exitForm(evt);       }     });   }   /*     P2PDashboard uses this to handle GUI object events.   */   private void configureGroupEvents()   {     // group JList event     groupList.setSelectionMode (ListSelectionModel.SINGLE_SELECTION);     groupList.addListSelectionListener (new ListSelectionListener() {       public void valueChanged(ListSelectionEvent e)       {         if (e.getValueIsAdjusting()) {           return;         }         JList list = (JList)e.getSource();         // whenever a group is selected,         // retrieve its corresponding peer list and         // display it.         if (list.isSelectionEmpty() == false) {           String group = (String)list.getSelectedValue();           SortedListModel peers = (SortedListModel) groupHT.get(group);           peerList.setModel(peers);         }       }     });     // group Add JButton event     groupAddButton.addActionListener(new ActionListener() {       public void actionPerformed(ActionEvent e)       {         String group = groupAddTextField.getText();         SortedListModel list = null;         if (checkAddRules(group) == false) {           return;         }         list = (SortedListModel)groupList.getModel();         // ensure new group does not already exist         if (list.contains(group) == false) {           list.addElement(group);           addGroup(group);           SortedListModel slm = new SortedListModel();           groupHT.put(group, slm);           groupList.setModel(list);           groupList.setSelectedValue(group, true);           peerList.clearSelection();         }         else {           handleError("Group `" + group + "` already in use.",                       "Invalid group name", null, false);         }         groupAddTextField.setText("");       }     });     // peer Flush JButton event     groupFlushButton.addActionListener(new ActionListener() {       public void actionPerformed(ActionEvent e)       {         // remove all groups except the netPeerGroup         SortedListModel list = (SortedListModel) groupList.getModel();         Enumeration enum = list.elements();         String group = null;         while (enum.hasMoreElements())         {           group = (String)enum.nextElement();           if (group.equals(defaultGroupName) == false) {             list.removeElement(group);             groupHT.remove(group);           }         }         groupList.setModel(list);         groupList.setSelectedValue(defaultGroupName, true);         peerList.clearSelection();         // flush actual local group advertisements         groupDiscovery.flushGroupInfo();       }     });     // group Remove JButton event     groupRemoveButton.addActionListener(new ActionListener() {       public void actionPerformed(ActionEvent e)       {         String group = (String)groupList.getSelectedValue();         if (group == null || group.equals("") == true ||             group.equals(defaultGroupName)) {           return;         }         SortedListModel list = (SortedListModel) groupList.getModel();         list.removeElement(group);         groupList.setModel(list);         groupList.setSelectedValue(defaultGroupName, true);         peerList.clearSelection();         removeAdvertisement(group, false);       }     });     // group Discovery JButton event     groupDiscoveryButton.addActionListener (new ActionListener() {       public void actionPerformed(ActionEvent e)       {         // initiate local group discovery         if (groupLocalRadioButton.isSelected()) {           groupDiscovery.setLocalDiscovery(true);           groupDiscovery.run();         }         // initiate remote group discovery         else if (groupRemoteRadioButton.isSelected()) {           groupDiscovery.setLocalDiscovery(false);           groupDiscovery.run();         }       }     });   }   /*     P2PDashboard uses this to handle peer GUI object events.    */   private void configurePeerEvents()   {     // peer JList event     peerList.setSelectionMode (ListSelectionModel.SINGLE_SELECTION);     peerList.addListSelectionListener (new ListSelectionListener() {       public void valueChanged(ListSelectionEvent e)       {         JList list = (JList)e.getSource();         String selectedPeer = (String)list.getSelectedValue();         if (e.getValueIsAdjusting() || displayPeerGroups == false) {           return;         }         // whenever a peer is selected,         // retrieve its corresponding group list and         // display it.         if (list.isSelectionEmpty() == false) {           SortedListModel peerInGroup = new SortedListModel();           SortedListModel peers = null;           String group = null;           Enumeration keys = groupHT.keys();           while (keys.hasMoreElements())           {             group = (String)keys.nextElement();             peers = (SortedListModel)groupHT.get(group);             if (peers.contains(selectedPeer) == true) {              peerInGroup.addElement(group);             }           }           groupList.setModel(peerInGroup);           groupList.clearSelection();         }       }     });     // peer Add JButton event     peerAddButton.addActionListener(new ActionListener() {       public void actionPerformed(ActionEvent e)       {         String peer = peerAddTextField.getText();         String group = (String)groupList.getSelectedValue();         // allow defaultPeerName to be added to new groups         if (peer != null && !peer.equals("") &&             group != null && !group.equals("") &&             peer.equals(defaultPeerName) &&             !group.equals(defaultGroupName)) {            System.out.println ("Adding " + peer + " to group '" + group + "'");         }         // default peer name checking         else if (checkAddRules(peer) == false ||                  group == null || group.equals("") == true) {           handleError("Invalid peer name.",                       "Invalid peer ", null, false);           return;         }         // do not allow a peer to be the same name as the         // currently selected group         if (peer.equals(group)) {           handleError("Peer cannot be same name as group.",                       "Invalid peer ", null, false);           return;         }         // retrieve peer list of currently selected group         SortedListModel list = (SortedListModel)peerList.getModel();         // ensure new peer does not already exist         if (list.contains(peer) == false) {           list.addElement(peer);           peerList.setModel(list);           groupHT.put(group, list);           addPeer(peer);         }         else {           handleError("Peer `" + peer + "` already in use.",                       "Invalid peer ", null, false);         }         peerAddTextField.setText("");       }     });     // peer Flush JButton event     peerFlushButton.addActionListener(new ActionListener() {       public void actionPerformed(ActionEvent e)       {         // remove every peer in every group         // except defaultPeerName in the netPeerGroup         Enumeration keys = groupHT.keys();         Enumeration enum = null;         SortedListModel peers = null;         String group = null;         String peer = null;         while (keys.hasMoreElements())         {           group = (String)keys.nextElement();           peers = (SortedListModel)groupHT.get(group);           enum = peers.elements();           while (enum.hasMoreElements())           {             peer = (String)enum.nextElement();             if (peer.equals(defaultPeerName) == true &&                 group.equals(defaultGroupName) == true) {                 System.out.println (defaultPeerName + " not flushed from " +  defaultGroupName);             }             else peers.removeElement(peer);             }           groupHT.put(group, peers);         }         groupList.setSelectedValue(defaultGroupName, true);         peerList.clearSelection();         // remove all peer advertisements         peerDiscovery.flushPeerInfo();       }     });     // peer group display JCheckBox event     peerCheckBox.addItemListener(new ItemListener() {       public void itemStateChanged(ItemEvent e)       {         // display all peers from every group         // so that when we select a peer, we can         // show the groups it belongs to.         if (e.getStateChange() == ItemEvent.SELECTED) {           displayPeerGroups = true;           Enumeration keys = groupHT.keys();           Enumeration enum = null;           String group = null;           String peer = null;           SortedListModel allPeers = new SortedListModel();           SortedListModel peers = null;           while (keys.hasMoreElements())           {             group = (String)keys.nextElement();             peers = (SortedListModel)groupHT.get(group);             enum = peers.elements();             while (enum.hasMoreElements())             {                peer = (String)enum.nextElement();                if (allPeers.contains(peer) == false) {                  allPeers.addElement(peer);                }             }           }           peerList.setModel(allPeers);           peerList.setSelectedValue(defaultPeerName, true);           groupList.clearSelection();         }         // remove, leave peer might occur now         // so allow a group and a peer to be selected.         else {           displayPeerGroups = false;           Enumeration keys = groupHT.keys();           String group = null;           SortedListModel groups = new SortedListModel();           while (keys.hasMoreElements())           {             group = (String)keys.nextElement();             groups.addElement(group);           }           groupList.setModel(groups);           groupList.setSelectedValue(defaultGroupName, true);           peerList.clearSelection();         }       }     });     // peer Remove JButton event     peerRemoveButton.addActionListener(new ActionListener() {       public void actionPerformed(ActionEvent e)       {         String group = (String)groupList.getSelectedValue();         String peer = (String)peerList.getSelectedValue();         if (peer == null || peer.equals("") == true ||             group == null || group.equals("") == true) {           handleError("Please unselect the `Groups` check box.!",                       "Remove failed", null, false);           return;         }         if ((peer.equals(defaultPeerName) == true &&              group.equals(defaultGroupName) == true)) {           handleError("Cannot remove local peer from netPeerGroup!",                       "Remove failed", null, false);           return;         }         // retrieve peer list of currently selected group         SortedListModel list = (SortedListModel) peerList.getModel();         list.removeElement(peer);         peerList.setModel(list);         groupHT.put(group, list);       groupList.setSelectedValue(defaultGroupName, true);       peerList.clearSelection();         removeAdvertisement(peer, true);       }     });     // peer Discovery JButton event    peerDiscoveryButton.addActionListener(new ActionListener() {       public void actionPerformed(ActionEvent e)       {         // initiate local peer discovery         if (peerLocalRadioButton.isSelected()) {           peerDiscovery.setLocalDiscovery(true);           peerDiscovery.run();         }         // initiate remote peer discovery         else if (peerRemoteRadioButton.isSelected()) {           peerDiscovery.setLocalDiscovery(false);           peerDiscovery.run();         }       }     });   }   /*    *Exit the application.    */   private void exitForm(WindowEvent e)   {     System.exit(0);   }   private void handleError(String msg, String title,                            Exception e, boolean exitSystem)   {     if (msg == null || title == null ||         msg.equals("") == true || title.equals("") == true) return;     if (e != null) e.printStackTrace();     JOptionPane.showMessageDialog(frame, msg, title, JOptionPane.ERROR_MESSAGE);     if (exitSystem) System.exit(1);   }   /******************************************/   /* Peer and Group List Validation Methods */   /******************************************/   private boolean checkAddRules(String s)   {     boolean check = true;     if (s == null || s.equals("") == true ||         s.equals(defaultGroupName) == true||         s.equals(defaultPeerName) == true) {       check=false;     }     return check;   }   /*****************/   /*  JXTA Methods */   /*****************/   /*    *Initialize the default NetPeerGroup that our    *local peer belongs to.    */   public void initializeNetPeerGroup()   {     try {       netPeerGroup = PeerGroupFactory.newNetPeerGroup();       discovery = netPeerGroup.getDiscoveryService();     }     catch (PeerGroupException e) {       handleError("netPeerGroup creation failed!", "NetPeerGroup", e, true);     }     // Print out useful local peer/group information     System.out.println("JXTA group = " + netPeerGroup.getPeerGroupName());     System.out.println("Group ID = " + netPeerGroup.getPeerGroupID().toString());     System.out.println("Peer name = " + netPeerGroup.getPeerName());     System.out.println("Peer ID = " + netPeerGroup.getPeerID().toString());     System.out.println("\n\n");   }   /*   *Initialize the peer and group discovery services for   *handling local and remote discovery events and messages.   */   public void initializeDiscovery()   {     SortedListModel list = null;     //Save default peer and group name     defaultGroupName = netPeerGroup.getPeerGroupName();     defaultPeerName = netPeerGroup.getPeerName();     //Group Discovery     groupDiscovery = new GroupDiscovery(netPeerGroup, discovery, groupList,  defaultGroupName);     groupDiscovery.startJxta();     // add netPeerGroup to group list in GUI     list = (SortedListModel)groupList.getModel();     list.addElement(defaultGroupName);     groupList.setModel(list);     // create new peer list for group netPeerGroup     list = new SortedListModel();     list.addElement(defaultPeerName);     groupHT.put(defaultGroupName, list);     groupList.setSelectedValue(defaultGroupName, true);     // Peer Discovery     peerDiscovery = new PeerDiscovery(netPeerGroup, discovery, peerList, defaultPeerName);     peerDiscovery.startJxta();     // Add defaultPeerName to peer list in the GUI     list = (SortedListModel)peerList.getModel();     list.addElement(defaultPeerName);     peerList.setModel(list);     peerList.clearSelection();   }   /*    *Creates a peer and publishes this peer locally    *and remotely.    */   public void addPeer(String peer)   {     // create new peer     PeerAdvertisement peerAdv = new PeerAdv();     peerAdv.setName(peer);     // using PeerGroupID.defaultNetPeerGroupID because     // PeerGroup.getGroupID returns ID and we can't resolve     // compilation or runtime issues with using     // new PeerID(PeerGroupID) method.     // Casting the ID to PeerGroupID will work with new     // PeerID(PeerGroupID) but causes runtime     // cast class exception.     // So we will just default all new peers have     // the defaultNetPeerGroupID for their group.     PeerID peerID = new PeerID (PeerGroupID.defaultNetPeerGroupID);     peerAdv.setPeerID(peerID);     peerAdv.setPeerGroupID (PeerGroupID.defaultNetPeerGroupID);     //Announce new peer.     try {       discovery.publish(peerAdv, DiscoveryService.PEER);       discovery.remotePublish (peerAdv, DiscoveryService.PEER);     }     catch (IOException e) {       handleError("Adding peer `" + peer + "` failed!", "Adding failed", e, false);     }   }   /*    *Remove a peer's credentials from the local cache.    */   public void removeAdvertisement(String s, boolean peer)   {     int type = DiscoveryService.PEER;     if (peer == false) {         type = DiscoveryService.GROUP;     }     Enumeration enum = null;     PeerGroupAdvertisement groupAdv = null;     PeerAdvertisement peerAdv = null;     try {       enum = discovery.getLocalAdvertisements (type, "Name", s);       if (enum.hasMoreElements()) {         if (peer == false) {           groupAdv = (PeerGroupAdvertisement) enum.nextElement();           discovery.flushAdvertisements (groupAdv.getPeerGroupID().toString(), type);         }         else {           peerAdv = (PeerAdvertisement) enum.nextElement();           discovery.flushAdvertisements (peerAdv.getPeerID().toString(), type);         }       }     }     catch (IOException e) {       handleError("Remove of peer or group failed!", "Removal failed", e, false);     }   }   /*    *Create a new group and publishes this group    *locally and remotely.    */   public PeerGroup addGroup(String group)   {     ModuleImplAdvertisement mia = null;     PeerGroup peerGroup = null;     PeerGroupAdvertisement pga = null;     try {       // create new group       mia = netPeerGroup. getAllPurposePeerGroupImplAdvertisement();       peerGroup = netPeerGroup.newGroup(null, mia, group,                                   group + " description");       // announce new group       pga = peerGroup.getPeerGroupAdvertisement();       discovery.publish(pga, DiscoveryService.GROUP);       discovery.remotePublish(pga, DiscoveryService.GROUP);       netPeerGroup.newGroup(pga);     }     catch (IOException e) {       handleError("Group `" + group + "` could not be added!.",                   "Exception during group add", e, false);     }     catch (PeerGroupException e) {       handleError("Group `" + group + "` could not be added!.",                   "Exception during group add", e, false);     }     catch (Exception e) {       handleError("Group `" + group + "` could not be added!.",                   "Exception during group add", e, false);     }     return peerGroup;   } } 

Details of the PeerDiscovery Class

The PeerDiscovery class is responsible for the local and remote discovery of peers, as well as for updating the peer information in the GUI. The PeerDiscovery class implements the Runnable and DiscoveryListener interfaces and the following methods:

• The updateGUI(Boolean stringCast, Enumeration enum) method updates the peer GUI by adding or removing peers

• The flushPeerInfo() method flushes the information in the local peer cache

• The run() method uses a thread to discover peers locally or remotely on demand

• The discoveryEvent(DiscoveryEvent e) method handles remote discovery messages

• The setLocalDiscovery(boolean local) method sets the discovery to be local or remote

• The PeerDiscovery(PeerGroup netPeerGroup, DiscoveryService discovery, Jlist peerList, String defaultPeerName) method creates a new PeerDiscovery object

Listing 19.2 presents the code for PeerDiscovery.java.

Listing 19.2 PeerDiscovery.java

 import java.io.InputStream; import java.io.IOException; import java.io.ByteArrayInputStream; import java.lang.String; import java.util.Enumeration; import javax.swing.JList; import net.jxta.document.Advertisement; import net.jxta.document.AdvertisementFactory; import net.jxta.document.MimeMediaType; import net.jxta.discovery.DiscoveryService; import net.jxta.discovery.DiscoveryListener; import net.jxta.discovery.DiscoveryEvent; import net.jxta.exception.PeerGroupException; import net.jxta.peergroup.PeerGroup; import net.jxta.peergroup.PeerGroupFactory; import net.jxta.protocol.DiscoveryResponseMsg; import net.jxta.protocol.PeerAdvertisement; /*  *PeerDiscovery  *Responsible for local and remote discovery of peers.  *Also responsible for updating the peer info in the GUI.  */ public class PeerDiscovery implements Runnable, DiscoveryListener {   // necessary links to important local peer information   private PeerGroup netPeerGroup;   private DiscoveryService discovery;   private PeerAdvertisement peerAdv;   // link to peer GUI list   private JList peerList;   private String defaultPeerName;   // link to GUI discovery selection type (local or remote)   private boolean local;   /*    *Update peer GUI for adding/removing peers    */   private void updateGUI(boolean stringCast, Enumeration enum)   {     String str = null;     PeerAdvertisement newAdv = null;     MimeMediaType mmt = new MimeMediaType("text/xml");     SortedListModel peers = (SortedListModel)peerList.getModel();     while (enum.hasMoreElements())     {       // Processing String objects       if (stringCast) {         str = (String)enum.nextElement();         try {           // create an advertisement for each element           newAdv = (PeerAdvertisement) AdvertisementFactory.newAdvertisement (mmt, new  ByteArrayInputStream(str.getBytes()));         }         catch (IOException ioe) {           System.out.println ("Error parsing response element!");           ioe.printStackTrace();           continue;         }       }       // Processing PeerAdvertisement objects       else  {         newAdv = (PeerAdvertisement)enum.nextElement();       }       System.out.println("Discovered peer = " + newAdv.getName());       // found a new peer, add them to the peerList       if (peers.contains(newAdv.getName()) == false) {         peers.addElement(newAdv.getName());         System.out.println("Discovered peer = " + newAdv.getName() + " added");       }     }     // update the GUI     peerList.setModel(peers);     peerList.setSelectedValue(defaultPeerName, true);   }   /*    *Start JXTA method    */   public void startJxta()   {     // flush local JXTA cache     flushPeerInfo();   }   /*    *Flush local peer cache information    */   public void flushPeerInfo()   {     try {       discovery.flushAdvertisements (null, DiscoveryService.PEER);     }     catch (IOException e) {       e.printStackTrace();     }   }   /*    *On demand, discover peers locally or remotely    *via a thread.    */   public void run()   {     Enumeration enum = null;     SortedListModel peers = (SortedListModel)peerList.getModel();     try {       //Add ourselves as a discoverylistener for       //discovery response events.       discovery.addDiscoveryListener(this);       // check local cache for peer       if (local) {         enum = discovery.getLocalAdvertisements (DiscoveryService.PEER, null, null);         if (enum == null || enum.hasMoreElements() == false) {           System.out.println ("No local advertisements found");         }         System.out.println ("update GUI peer discovery now");         //Update peer list in GUI         updateGUI(false, enum);       }       //Wait 10 seconds per remote discovery       else {         discovery.getRemoteAdvertisements(null, DiscoveryService.PEER, null, null, 10,  this);       try {           Thread.sleep(10 * 1000);         }         catch (Exception e) {         }       }     }     catch (Exception e) {       e.printStackTrace();     }   }   /*    *Handle remote discovery messages.    */   public void discoveryEvent(DiscoveryEvent e)   {     DiscoveryResponseMsg drm = e.getResponse();     String response = drm.getPeerAdv();     InputStream is = null;     PeerAdvertisement peerAdv = null;     MimeMediaType mmt = new MimeMediaType("text/xml");     try {       // create a peer advertisement       is = new ByteArrayInputStream(response.getBytes());       peerAdv = (PeerAdvertisement) AdvertisementFactory.newAdvertisement(mmt, is);       System.out.println ("[ Received discovery response [" +            drm.getResponseCount() +            " elements] from peer : " +              peerAdv.getName() + " ]");     }     catch (IOException ioe) {       System.out.println("Error parsing remote peer's advertisement!");       ioe.printStackTrace();       return;     }     // update peers in GUI     updateGUI(true, drm.getResponses());   }   /*    *set discovery to be local or remote    *local = true   > search is local    *local = false  > search is remote    */   public void setLocalDiscovery(boolean local)   {     this.local = local;   }   /*    *Creates new PeerDiscovery object.    */   public PeerDiscovery(PeerGroup netPeerGroup, DiscoveryService discovery, JList peerList,  String defaultPeerName)   {     this.netPeerGroup = netPeerGroup;     this.discovery = discovery;     this.peerList = peerList;     this.defaultPeerName = defaultPeerName;     local = true;   } } 

Details of the GroupDiscovery.java Class

The GroupDiscovery class is responsible for handling local and remote discovery of groups, as well as updating the group information on the GUI.

The GroupDiscovery class implements the Runnable and DiscoveryListener interfaces. It uses the following methods:

• The updateGUI(boolean stringCast, Enumeration enum) method updates the GUI for adding and/or removing groups and respective peers under desired groups

• The startJXTA() method executes the flushGroupInfo() method to flush local group information in the cache

• The flushGroupInfo() method flushes local group information in the cache

• The run() method uses a thread to discover groups locally or remotely on demand

• The discoveryEvent(DiscoveryEvent e) method handles remote discovery messages

• The setLocalDiscovery(boolean local) method sets the discovery type to be local or remote

Listing 19.3 presents the code for GroupDiscovery.java.

Listing 19.3 GroupDiscovery.java

 import java.io.InputStream; import java.io.IOException; import java.io.ByteArrayInputStream; import java.lang.String; import java.util.Enumeration; import javax.swing.JList; import net.jxta.document.Advertisement; import net.jxta.document.AdvertisementFactory; import net.jxta.document.MimeMediaType; import net.jxta.discovery.DiscoveryService; import net.jxta.discovery.DiscoveryListener; import net.jxta.discovery.DiscoveryEvent; import net.jxta.exception.PeerGroupException; import net.jxta.peergroup.PeerGroup; import net.jxta.peergroup.PeerGroupFactory; import net.jxta.protocol.DiscoveryResponseMsg; import net.jxta.protocol.PeerAdvertisement; import net.jxta.protocol.PeerGroupAdvertisement; /*  *GroupDiscovery  *Responsible for local and remote discovery of groups.  *Also responsible for updating the group information  *in the GUI.  */ public class GroupDiscovery implements Runnable, DiscoveryListener {   // necessary links to important group information   private PeerGroup netPeerGroup;   private DiscoveryService discovery;   private PeerAdvertisement peerAdv;   // link to group tree GUI   private JList groupList;   private String defaultGroupName;   // link to GUI discovery selection type (local or remote)   private boolean local;   /*    *Update group GUI for adding/removing groups and    *respective peers under groups.    */   private void updateGUI (boolean stringCast, Enumeration enum)   {     String str = null;     PeerGroupAdvertisement newAdv = null;     MimeMediaType mmt = new MimeMediaType("text/xml");     SortedListModel groups = (SortedListModel)groupList.getModel();     while (enum.hasMoreElements())     {       // Processing String objects       if (stringCast) {         str = (String)enum.nextElement();     try {           // create an advertisement from each element           newAdv = (PeerGroupAdvertisement) AdvertisementFactory.newAdvertisement (mmt,  new ByteArrayInputStream(str.getBytes()));         }         catch (IOException ioe) {           System.out.println ("Error parsing response element!");           ioe.printStackTrace();           continue;         }       }      // Processing PeerGroupAdvertisement objects      else {        newAdv = (PeerGroupAdvertisement)enum.nextElement();      }      System.out.println("Discovered group = " + newAdv.getName());      // found a new group, add them to the groupList      if (groups.contains(newAdv.getName()) == false) {        groups.addElement(newAdv.getName());        System.out.println("Discovered group = " + newAdv.getName() + " added");      }     }     // update the GUI     groupList.setModel(groups);     groupList.setSelectedValue(defaultGroupName, true);   }   /*    *Start JXTA method.    */   public void startJxta()   {     // flush local group cache     flushGroupInfo();   }   /*    *Flush local group cache information.    */   public void flushGroupInfo()   {     try {       discovery.flushAdvertisements (null, DiscoveryService.GROUP);     }     catch (IOException e) {       e.printStackTrace();     }   }   /*    *On demand, discover groups locally or remotely    *via a thread.    */   public void run()   {     Enumeration enum = null;     PeerGroupAdvertisement pga = null;     SortedListModel groups = (SortedListModel)groupList.getModel();     try {       //Add ourselves as a discoverylistener for       //discovery response events.       discovery.addDiscoveryListener(this);       // check local cache for peer       if (local) {         enum = discovery.getLocalAdvertisements (DiscoveryService.GROUP, null, null);         if (enum == null || enum.hasMoreElements() == false) {           System.out.println ("No local advertisements found");           return;         }         System.out.println ("update GUI group discovery now");         // update group list in GUI         updateGUI(false, enum);       }       // wait 10 seconds per remote discovery       else {         discovery.getRemoteAdvertisements (null, DiscoveryService.GROUP, null, null, 10,  this);         try {           Thread.sleep(10 * 1000);         }         catch (Exception e) {         }       }     }     catch (Exception e)     {       e.printStackTrace();     }   }   /*    *Handle remote discovery messages.    */   public void discoveryEvent(DiscoveryEvent e)   {     DiscoveryResponseMsg drm = e.getResponse();     String response = drm.getPeerAdv();     InputStream is = null;     MimeMediaType mmt = new MimeMediaType("text/xml");     try {       //Create a group advertisement.       is = new ByteArrayInputStream(response.getBytes());       peerAdv = (PeerAdvertisement) AdvertisementFactory.newAdvertisement(mmt, is);       System.out.println("[ Received discovery response [" + drm.getResponseCount() +"  elements] from group: " + peerAdv.getName() + " ]");     }     catch (IOException ioe) {       System.out.println("Error parsing remote peer's advertisement!");       ioe.printStackTrace();       return;     }     // update groups in GUI     updateGUI(true, drm.getResponses());   }   /*    *Set discovery type    *local = true   > search is local     *local = false  > search is remote     */   public void setLocalDiscovery(boolean local)   {     this.local = local;   }  /*   *Creates new GroupDiscovery object.   */   public GroupDiscovery(PeerGroup netPeerGroup, DiscoveryService discovery, JList  groupList, String defaultGroupName)   {     this.netPeerGroup = netPeerGroup;     this.discovery = discovery;     this.groupList = groupList;     this.defaultGroupName = defaultGroupName;     local = true;   } } 

Details of the SortedListModel Class

The SortedListModel class is responsible for creating a tree of listmodel objects and storing them in a sorted set. It sorts the listmodel objects that are used to manage either peer or group lists.

The SortedListModel class employs the following methods:

• The getSize() method to obtain the size of the list

• The getElementAt(int index) method to get the desired element at the specified index

• The addElement(Object element) method to add individual elements to the list

• The addAll(Object elements[]) method to add an array of elements to the list

• The clear method to clear the list

• The contains(Object element) method to check whether the list contains a specific element

• The elements() method to obtain an Enumeration of the elements in the list

• The firstElement() method to obtain the first element in the list

• The iterator() method to obtain an Iterator for the elements in the list

• The lastElement() method to obtain the last element in the list

• The removeElement(Object element) method to check whether an element has been removed

Listing 19.4 presents the code for SortedListModel.java.

Listing 19.4 SortedListModel.java

 // Original source from : // // Copyright 1999 MageLang Institute // $Id //depot/main/src/edu/modules/Collections/magercises/Jlist /Solution/ SortedListModel.java#2 $ // // Source has been modified for JXTA dashboard. // import javax.swing.*; import java.util.*; public class SortedListModel extends AbstractListModel {   // Define a SortedSet   SortedSet model;   public SortedListModel()   {     // Create a TreeSet     // Store it in SortedSet variable     model = new TreeSet();   }   // ListModel methods   public int getSize()   {     // Return the model size     return model.size();   }   public Object getElementAt(int index)   {     // Return the appropriate element     return model.toArray()[index];   }   // Other methods   public void addElement(Object element)   {     if (model.add(element)) {       fireContentsChanged(this, 0, getSize());     }   }   public void addAll(Object elements[])   {     Collection c = Arrays.asList(elements);     model.addAll(c);     fireContentsChanged(this, 0, getSize());   }   public void clear()   {     model.clear();     fireContentsChanged(this, 0, getSize());   }   public boolean contains(Object element)   {     return model.contains(element);   }   public Enumeration elements()   {     // Return the appropriate element     Vector v = new Vector();     int size = model.size();     for (int i = 0; i < size; i++)     {      v.addElement(model.toArray()[i]);     }     return v.elements();   }   public Object firstElement()   {     // Return the appropriate element     return model.first();   }   public Iterator iterator()   {     return model.iterator();   }   public Object lastElement()   {     // Return the appropriate element     return model.last();   }   public boolean removeElement(Object element)   {     boolean removed = model.remove(element);     if (removed) {       fireContentsChanged(this, 0, getSize());     }     return removed;   } }