/**

* $Id: Share.java,v 1.9 2012/01/13 12:40:38 david Exp $

* Copyright (c) 2007-2012, JGraph Ltd

*/

package com.mxgraph.examples.web;

import java.io.IOException;

import java.io.PrintWriter;

import java.net.URLDecoder;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

import javax.servlet.http.HttpSessionBindingEvent;

import javax.servlet.http.HttpSessionBindingListener;

import org.mortbay.jetty.Request;

import org.w3c.dom.Document;

import org.w3c.dom.Element;

import org.w3c.dom.Node;

import com.mxgraph.io.mxCodecRegistry;

import com.mxgraph.model.mxGraphModel;

import com.mxgraph.model.mxICell;

import com.mxgraph.sharing.mxSession;

import com.mxgraph.sharing.mxSharedGraphModel;

import com.mxgraph.sharing.mxSharedState;

import com.mxgraph.util.mxXmlUtils;

/**

* This servlet demonstrates the sharing of diagrams across a number of

* clients. The servlet itself does not have an object representation of the

* graph in memory, it only serves as a dispatcher for the XML among the

* clients.

*

* To integrate sharing with a client application, an mxSession must be created

* and configured to handle cell identities and more. This is all done in the

* mxEditor.connect method, which returns the session object being used to

* connect the model to the backend. Note that it is possible to attach

* multiple sessions to one editor and graph model.

*

* When the graph model is changed in a shared client, the changes are encoded

* into XML and then sent to the server in a POST request. The server then gets

* a list of clients which are connected to the same diagram, and sends the

* encoded changes to those clients. (Note that the sender will not get

* notified of his own changes in the default mode.)

*

* When the client receives such a set of changes, it decodes them and executes

* them on its local model, bypassing the command history of local changes.

* This means the client immediately sees the changes, but pressing undo will

* only undo the last local change of that specific client.

*

* To use the example, the respective session URLs must be assigned in the

* mxEditor either programmatically or by use of the same config file as above.

* Note that it is possible to integrate both, image creating and diagram

* sharing into the same client by assigning the respective attributes in the

* mxEditor node in the config file. For diagram sharing, the following

* member variables are used: mxEditor.urlInit, mxEditor.urlPoll and

* mxEditor.urlNotify.

*/

public class Share extends HttpServlet

{

/**

*

*/

private static final long serialVersionUID = -3367340615965785051L;

/**

*

*/

protected static String SESSION_ID = "MXSESSIONID";

/**

* Set this to true to create a model instance on the server side and keep

* it in sync with the client's model. If this is false then the server

* stores the initial state and all deltas separately without having a

* synced server-side model instance.

*/

protected static boolean useSharedModel = false;

/**

*

*/

protected static mxSharedState sharedResource = (useSharedModel) ? new mxSharedGraphModel(

new mxGraphModel()

{

protected Object valueForCellChanged(Object cell, Object value)

{

Object previous = ((mxICell) cell).getValue();

if (!(value instanceof Node) && previous instanceof Element)

{

Object tmp = ((Element) previous).getAttribute("label");

if (value == null)

{

((Element) previous).removeAttribute("label");

}

else

{

((Element) previous).setAttribute("label",

String.valueOf(value));

}

previous = tmp;

}

else

{

((mxICell) cell).setValue(value);

}

return previous;

}

})

: new mxSharedState(

"<mxGraphModel><root><Workflow label=\"Diagram\" id=\"0\"></Workflow><Layer "

+ "label=\"Default Layer\" id=\"1\"><mxCell parent=\"0\" /></Layer></root></mxGraphModel>");

// Associates the graph model codec with the above anonymous class

static

{

mxCodecRegistry.addAlias("com.mxgraph.examples.web.Share$1",

"mxGraphModel");

}

protected void doPost(HttpServletRequest request,

HttpServletResponse response) throws ServletException, IOException

{

String xml = URLDecoder.decode(request.getParameter("xml"), "UTF-8");

mxSession session = getSession(request);

Document doc = mxXmlUtils.parseXml(xml);

session.receive(doc.getDocumentElement());

response.setStatus(HttpServletResponse.SC_OK);

//System.out.println(session.getId() + " post xml=" + xml);

}

protected void doGet(HttpServletRequest request,

HttpServletResponse response) throws ServletException, IOException

{

mxSession session = getSession(request);

PrintWriter res = response.getWriter();

String query = getQueryString(request);

// Redirects the client to the actual static diagram editor. The diagram editor

// loads the configuration which contains one hook to request more configuration

// data at the server. This request is implemented in Config.java to deliver the

// configuration required to access this servlet for sharing and Export.java for

// creating images.

if (query.equalsIgnoreCase("start"))

{

response.sendRedirect("/mxgraph/javascript/examples/editors/diagrameditor.html");

((Request) request).setHandled(true);

}

else if (query.equalsIgnoreCase("reset"))

{

sharedResource.resetDelta();

res.println("Diagram reset");

}

else

{

response.setContentType("text/xml;charset=UTF-8");

response.setHeader("Pragma", "no-cache"); // HTTP 1.0

response.setHeader("Cache-control", "private, no-cache, no-store");

response.setHeader("Expires", "0");

if (query.equalsIgnoreCase("init"))

{

String xml = session.init();

//System.out

// .println("session " + session.getId() + " xml=" + xml);

res.println(xml);

}

else

{

try

{

String xml = session.poll();

//System.out.println("session " + session.getId() + " xml="

// + xml);

res.println(xml);

}

catch (InterruptedException e)

{

throw new ServletException(e);

}

}

}

response.setStatus(HttpServletResponse.SC_OK);

}

/**

* Helper method that never returns null. If there is no query in the given

* request then an empty string will be returned.

*/

protected String getQueryString(HttpServletRequest request)

{

String query = request.getQueryString();

if (query == null)

{

query = "";

}

return query;

}

/**

* Returns the session for the given request.

*/

protected mxSession getSession(HttpServletRequest req)

{

HttpSession httpSession = req.getSession(true);

mxSession session = (mxSession) httpSession.getAttribute(SESSION_ID);

if (session == null)

{

session = new mxBoundSession(httpSession.getId(), sharedResource);

httpSession.setAttribute(SESSION_ID, session);

httpSession.setMaxInactiveInterval(20);

}

return session;

}

/**

* Implements a session with some lifecycle debugging output.

*/

public class mxBoundSession extends mxSession implements

HttpSessionBindingListener

{

public mxBoundSession(String id, mxSharedState diagram)

{

super(id, diagram);

}

public void valueBound(HttpSessionBindingEvent arg0)

{

//System.out.println("session " + id + " created");

}

public void valueUnbound(HttpSessionBindingEvent arg0)

{

//System.out.println("session " + id + " destroyed");

destroy();

}

}

}