Implemented request attachment: If a request with the same

user, path and input data is already being evaluated, the request is
attached to that evaluation instead of starting a new one.
This should fix the very common double- or multiple click problem,
among others.

src/helma/framework/RequestTrans.java

@@ -17,8 +17,11 @@ public class RequestTrans implements Serializable {
     public String path;
     public String session;
     private Hashtable values;
+
     // this is used to hold the EcmaScript form data object
     public transient Object data;
+    // when was execution started on this request?
+    public transient long startTime;
 
     public RequestTrans () {
 	super ();
@@ -49,4 +52,24 @@ public class RequestTrans implements Serializable {
 	return values;
     }
 
+    public int hashCode () {
+	return session == null ? super.hashCode () : session.hashCode ();
+    }
+
+
+    /**
+     * A request is considered equal to another one if it has the same user, path,
+     * and request data. This is used to evaluate multiple simultanous requests only once
+     */
+    public boolean equals (Object what) {
+	try {
+	    RequestTrans other = (RequestTrans) what;
+	    return (session.equals (other.session) &&
+		path.equalsIgnoreCase (other.path) &&
+		values.equals (other.getReqData ()));
+	} catch (Exception x) {
+	    return false;
+	}
+    }
+
 }

src/helma/framework/ResponseTrans.java

@@ -142,12 +142,28 @@ public class ResponseTrans implements Serializable {
 
 
     /**
-     * This has to be called after writin to this response has finished and before it is shipped back to the
+     * This has to be called after writing to this response has finished and before it is shipped back to the
      * web server. Transforms the string buffer into a char array to minimize size.
      */
-    public void close () {
-	if (buffer != null)
+    public synchronized void close () {
+	if (buffer != null) {
 	    response = new String (buffer).toCharArray();
+	    buffer = null; // make sure this is done only once, even with more requsts attached
+	} else {
+	    response = new char[0];
+	}
+	notifyAll ();
+    }
+
+    /**
+     * If we just attached to evaluation we call this instead of close because only the primary thread
+     * is responsible for closing the result
+     */
+    public synchronized void waitForClose () {
+	try {
+	    if (response == null)
+	        wait (10000l);
+	} catch (InterruptedException ix) {}
     }
 
     public String getContentString () {

src/helma/framework/core/Application.java

@@ -54,6 +54,9 @@ public class Application extends UnicastRemoteObject implements IRemoteApp, Runn
     long requestTimeout = 60000; // 60 seconds for request timeout.
     ThreadGroup threadgroup;
 
+    // Map of requesttrans -> active requestevaluators
+    Hashtable activeRequests;
+    
     protected String templateExtension, scriptExtension, actionExtension, skinExtension;
 
     // A transient node that is shared among all evaluators
@@ -124,6 +127,7 @@ public class Application extends UnicastRemoteObject implements IRemoteApp, Runn
 	    freeThreads.push (ev);
 	    allThreads.addElement (ev);
 	}
+	activeRequests = new Hashtable ();
 
 	typemgr = new TypeManager (this);
 	typemgr.check ();
@@ -229,9 +233,23 @@ public class Application extends UnicastRemoteObject implements IRemoteApp, Runn
 
 	ResponseTrans res = null;
 	RequestEvaluator ev = null;
+	// are we responsible for releasing the evaluator and closing the result?
+	boolean primaryRequest = false;
 	try {
-	    ev = getEvaluator ();
-	    res = ev.invoke (req, u);
+	    // first look if a request with same user/path/data is already being executed.
+	    // if so, attach the request to its output instead of starting a new evaluation
+	    // this helps to cleanly solve "doubleclick" kind of users
+	    ev = (RequestEvaluator) activeRequests.get (req);
+	    if (ev != null) {
+	        res = ev.attachRequest (req);
+	    }
+	    if (res == null) {
+	        primaryRequest = true;
+	        // if attachRequest returns null this means we came too late
+	        // and the other request was finished in the meantime
+	        ev = getEvaluator ();
+	        res = ev.invoke (req, u);
+	    }
 	} catch (ApplicationStoppedException stopped) {
 	    // let the servlet know that this application has gone to heaven
 	    throw stopped;
@@ -240,10 +258,14 @@ public class Application extends UnicastRemoteObject implements IRemoteApp, Runn
 	    res = new ResponseTrans ();
 	    res.write ("Error in application: <b>" + x.getMessage () + "</b>");
 	} finally {
-	    releaseEvaluator (ev);
+	    if (primaryRequest) {
+	        releaseEvaluator (ev);
+	        res.close ();  // this needs to be done before sending it back
+	    } else {
+	        res.waitForClose ();
+	    }
 	}
 
-	res.close ();  // this needs to be done before sending it back
 	return res;
     }
 

src/helma/framework/core/RequestEvaluator.java

@@ -533,18 +533,37 @@ public class RequestEvaluator implements Runnable {
 	this.user = user;
 	this.res = new ResponseTrans ();
 
-	checkThread ();
-	wait (app.requestTimeout);
- 	if (reqtype != NONE) {
-	    IServer.getLogger().log ("Stopping Thread for Request "+app.getName()+"/"+req.path);
-	    stopThread ();
-	    res.reset ();
-	    res.write ("<b>Error in application '"+app.getName()+"':</b> <br><br><pre>Request timed out.</pre>");
+	try {
+	    app.activeRequests.put (req, this);
+
+	    checkThread ();
+	    wait (app.requestTimeout);
+ 	    if (reqtype != NONE) {
+	        IServer.getLogger().log ("Stopping Thread for Request "+app.getName()+"/"+req.path);
+	        stopThread ();
+	        res.reset ();
+	        res.write ("<b>Error in application '"+app.getName()+"':</b> <br><br><pre>Request timed out.</pre>");
+	    }
+	} finally {
+	    app.activeRequests.remove (req);
 	}
 
 	return res;
     }
 
+    /**
+     * This checks if the Evaluator is already executing an equal request. If so, attach to it and
+     * wait for it to complete. Otherwise return null, so the application knows it has to run the request.
+     */
+    public synchronized ResponseTrans attachRequest (RequestTrans req) throws InterruptedException {
+	if (this.req == null || !this.req.equals (req) || reqtype == NONE)
+	    return null;
+	// we already know our response object
+	ResponseTrans r = res;
+	wait (app.requestTimeout);
+	return r;
+    }
+
 
     public synchronized Object invokeXmlRpc (String method, Vector args) throws Exception {
 	this.reqtype = XMLRPC;