/**
* $Id: mxSession.java,v 1.1 2012/11/15 13:26:50 gaudenz Exp $
* Copyright (c) 2007-2012, JGraph Ltd
*/
package com.mxgraph.sharing;
import com.mxgraph.sharing.mxSharedState.mxDiagramChangeListener;
import com.mxgraph.util.mxUtils;
import org.w3c.dom.Node;
/**
* Implements a session that may be attached to a shared diagram. The session
* contains a synchronized buffer which is used to hold the pending edits which
* are to be sent to a specific client. The update mechnism between the server
* and the client uses HTTP requests (polling). The request is kept on the server
* for an amount of time or wakes up / returns immediately if the buffer is no
* longer empty.
*/
public class mxSession implements mxDiagramChangeListener {
/**
* Default timeout is 10000 ms.
*/
public static int DEFAULT_TIMEOUT = 10000;
/**
* Holds the session ID.
*/
protected String id;
/**
* Reference to the shared diagram.
*/
protected mxSharedState diagram;
/**
* Holds the send buffer for this session.
*/
protected StringBuffer buffer = new StringBuffer();
/**
* Holds the last active time millis.
*/
protected long lastTimeMillis = 0;
/**
* Constructs a new session with the given ID.
*
* @param id Specifies the session ID to be used.
* @param diagram Reference to the shared diagram.
*/
public mxSession(String id, mxSharedState diagram) {
this.id = id;
this.diagram = diagram;
this.diagram.addDiagramChangeListener(this);
lastTimeMillis = System.currentTimeMillis();
}
/**
* Returns the session ID.
*/
public String getId() {
return id;
}
/**
* Initializes the session buffer and returns a string that represents the
* state of the session.
*
* @return Returns the initial state of the session.
*/
public synchronized String init() {
synchronized (this) {
buffer = new StringBuffer();
notify();
}
return getInitialMessage();
}
/**
* Returns an XML string that represents the current state of the session
* and the shared diagram. A globally unique ID is used as the session's
* namespace, which is used on the client side to prefix IDs of newly
* created cells.
*/
public String getInitialMessage() {
String ns = mxUtils.getMd5Hash(id);
StringBuffer result = new StringBuffer("<message namespace=\"" + ns + "\">");
result.append("<state>");
result.append(diagram.getState());
result.append("</state>");
result.append("<delta>");
result.append(diagram.getDelta());
result.append("</delta>");
result.append("</message>");
return result.toString();
}
/**
* Posts the change represented by the given XML string to the shared diagram.
*
* @param message XML that represents the change.
*/
public void receive(Node message) {
//System.out.println(getId() + ": " + mxUtils.getPrettyXml(message));
Node child = message.getFirstChild();
while (child != null) {
if (child.getNodeName().equals("delta")) {
diagram.processDelta(this, child);
}
child = child.getNextSibling();
}
/*System.out.println(mxUtils.getPrettyXml(new mxCodec()
.encode(((mxSharedGraphModel) diagram).getModel())));*/
}
/**
* Returns the changes received by other sessions for the shared diagram.
* The method returns an empty XML node if no change was received within
* 10 seconds.
*
* @return Returns a string representing the changes to the shared diagram.
*/
public String poll() throws InterruptedException {
return poll(DEFAULT_TIMEOUT);
}
/**
* Returns the changes received by other sessions for the shared diagram.
* The method returns an empty XML node if no change was received within
* the given timeout.
*
* @param timeout Time in milliseconds to wait for changes.
* @return Returns a string representing the changes to the shared diagram.
*/
public String poll(long timeout) throws InterruptedException {
lastTimeMillis = System.currentTimeMillis();
StringBuffer result = new StringBuffer("<message>");
synchronized (this) {
if (buffer.length() == 0) {
wait(timeout);
}
if (buffer.length() > 0) {
result.append("<delta>");
result.append(buffer.toString());
result.append("</delta>");
buffer = new StringBuffer();
}
notify();
}
result.append("</message>");
return result.toString();
}
/*
* (non-Javadoc)
* @see com.mxgraph.sharing.mxSharedDiagram.mxDiagramChangeListener#diagramChanged(java.lang.Object, org.w3c.dom.Node)
*/
public synchronized void diagramChanged(Object sender, String edits) {
if (sender != this) {
synchronized (this) {
buffer.append(edits);
notify();
}
}
}
/**
* Returns the number of milliseconds this session has been inactive.
*/
public long inactiveTimeMillis() {
return System.currentTimeMillis() - lastTimeMillis;
}
/**
* Destroys the session and removes its listener from the shared diagram.
*/
public void destroy() {
diagram.removeDiagramChangeListener(this);
}
}