LightStreamer with GWTQuery.

flybyGWT

I was wondering if anyone has come across and problem using light streamer in GWT when also inheriting the GWTQuery package? Simply inheriting the gwtQuery package has the end effect of causing a subscription to become null. Remove the gwtQuery inherits and the problem goes away.

Excerpts from <project>.gwt.xml

<add-linker name="xs" />

<inherits name='com.google.gwt.query.Query'/>

JS client error with gwtQuery inherited.

Thu Feb 06 16:01:52 GMT-600 2014 com.google.gwt.logging.client.LogConfiguration SEVERE: (TypeError) stack: $dialogBoxResult@http://**/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html:189$onSuccess@http://**/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html:1890$onResponseReceived@http://**/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html:16823$fireOnResponseReceived@http://1**/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html:8575onReadyStateChange@http://**/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html:8741$setOnReadyStateChange/this$static.onreadystatechange<@http:///**/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html:21062apply@http:///**/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html:6188entry0@http:///**/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html:6226entry_0/<@http://1/**/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html:6211 fileName: [url]http:///**/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html[/url] lineNumber: 189 columnNumber: 2: this$static.grid.subscription is null
com.google.gwt.core.client.JavaScriptException: (TypeError) stack: $dialogBoxResult@http:///**/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html:189$onSuccess@http://**/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html:1890$onResponseReceived@http:/**/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html:16823$fireOnResponseReceived@http:///**/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html:8575onReadyStateChange@http:///**/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html:8741$setOnReadyStateChange/this$static.onreadystatechange<@http:///loaddesk/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html:21062apply@http:///loaddesk/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html:6188entry0@http:///loaddesk/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html:6226entry_0/<@http:///loaddesk/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html:6211 fileName: [url]http:///loaddesk/773F7F6C1E017B4CFE8FCCE688B8F0AA.cache.html[/url] lineNumber: 189 columnNumber: 2: this$static.grid.subscription is null
at Unknown.$dialogBoxResult(Unknown Source)
at Unknown.$onSuccess(Unknown Source)
at Unknown.$onResponseReceived(Unknown Source)
at Unknown.$fireOnResponseReceived(Unknown Source)
at Unknown.onReadyStateChange(Unknown Source)
at Unknown.$setOnReadyStateChange/this$static.onreadystatechange<(Unknown Source)
at Unknown.apply(Unknown Source)
at Unknown.entry0(Unknown Source)
at Unknown.entry_0/<(Unknown Source)
at Unknown.anonymous(Unknown Source)

Giuseppe Corti

Hi flybyGWT,

Yes, you are right, I have tried to add the gwtQuery to our GWT StockList Demo and indeed, it stopped working.
But with a couple of tweaks it resumes to work again, in detail the steps that I followed are these:

1. Change the style for the Lighstreamer JavaScript library in use. You can build a suitable lightstreamer.js file from the online generator.
In that case be sure to include the LightstreamerClient, Subscription, and any other class used in your app and to flag the "Use namespaced globals" option.

2. In the source code of the Demo, every time a object of the Lightstreamer library should be instantiated add the prefix "$wnd.Lightstreamer.". For example:

[SYNTAX=JSCRIPT]var client = new $wnd.Lightstreamer.LightstreamerClient();[/SYNTAX]

3. Recompile the sources and run the application.

Please get back to me for any further explaination.

flybyGWT

I have taken the steps you have outlined and I am getting the same error.

I used the Online Generator with the LightStreamerClient, Subscription, and Use namedspaced globals options. (we are not using any other classes)

I copied the output of the generator and replaced the lightstreamer.js file contents with the generated output.

I changed all references to
[SYNTAX=JSCRIPT]var client = new $wnd.LightstreamerClient();[/SYNTAX] ->
[SYNTAX=JSCRIPT]var client = new $wnd.Lightstreamer.LightstreamerClient();[/SYNTAX]

I cleaned all the GWT output files, recompiled, and still received the same error. I then removed the <inherits name='com.google.gwt.query.Query'/> from the xml and recompiled/ran, and started noticing the call to new $wnd.Lightstreamer.LightstreamerClient(); was returning null.

Is there a change to the lightstreamer_globals.js that also needed to happen?

Thanks

Giuseppe Corti

Hi flybyGWT,

No, no changes to the generated library, you just need be sure that the new library file is correctly pointed from html page.

flybyGWT

I apologize i am taking this over from another developer so I am not entirely which scripts are suppose to be included.

Our html page only loads <script src="lightstreamer/lightstreamer_globals.js"></script>... Is that incorrect?

Thanks.

Giuseppe Corti

Only one file needs to be included and the filename where you saved the generated library should match with the <script> command in HTML page.
So, if you have saved the lib in "lightstreamer/lightstreamer.js", you should change html page in:

[SYNTAX=HTML]<script src="lightstreamer/lightstreamer.js"></script>[/SYNTAX]

flybyGWT

Thank you very much for the info. Changing to the lightstreamer.js script inclusion fix the problem with the LightStreamerClient returning null.

However the same error as before is popping up again. This is occurring when the gwt.xml is NOT including the GWTQuery inherit.

I have also verified that we are not port clashing... As i know that can cause the same error to be thrown.

/88DD3B1C31918427CB9FC421FC5294D2.cache.js lineNumber: 184 columnNumber: 2: this$static.grid.subscription is null
at Unknown.$dialogBoxResult(Unknown Source)
at Unknown.$onSuccess(Unknown Source)
at Unknown.$onResponseReceived(Unknown Source)
at Unknown.$fireOnResponseReceived(Unknown Source)
at Unknown.onReadyStateChange(Unknown Source)
at Unknown.$setOnReadyStateChange/this$static.onreadystatechange<(Unknown Source)
at Unknown.apply(Unknown Source)
at Unknown.entry0(Unknown Source)
at Unknown.entry_0/<(Unknown Source)
at Unknown.anonymous(Unknown Source)

Giuseppe Corti

The "$wnd.Lightstreamer." prefix have to be added every time you instantiate the "Subscription" class (just as for any other class of the library).

[SYNTAX=JSCRIPT]new $wnd.Lightstreamer.Subscription();[/SYNTAX]

flybyGWT

So in GWT we are first creating the client and storing it in a GWT JSO variable then passing the JSO subscription list to it (The JSO client) and calling subscribe.

private JavaScriptObject client;

...

this.client = this.createClient();

...

client.subscribe(grid);
...

private native JavaScriptObject createClient() /*-{
var client = new $wnd.Lightstreamer.LightstreamerClient(); ;
return client;
}-*/;

public void subscribe(LDFieldsSubscription sub) {
if (this.client == null) {
throw new IllegalStateException("LightstreamerClient failed to initialize properly");
}
this.subscribe(sub.getSubscription());
}

private native void subscribe(JavaScriptObject sub) /*-{
this.@com.company.project.application.client.ui.LightstreamerClient::client.subscribe(sub);
}-*/;

private native JavaScriptObject initSubscription(String[] itemList,
String[] fieldList, String subscriptionMode) /*-{

var that = this;
mySub = null;

mySub = new Subscription(subscriptionMode, itemList, fieldList);

mySub
.addListener({
onItemUpdate : function(itemUpdate) {
for (i = 0; i < fieldList.length; i++) {

// check whether the schema value is changed. If it's not, skip it
// unless a full data snapshot is being sent.
if (!itemUpdate.isValueChanged(fieldList)
&& !itemUpdate.isSnapshot()) {
continue;
}

var itemName = null;
itemName = itemUpdate.getItemName();

var value = null;
value = itemUpdate.getValue(fieldList);
if (value != null) {
that.@com.delta.acs.loaddesk.client.ui.LDFieldsSubscription::onItemUpdate(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String :Smile_Ad: (itemName, fieldList, value);
}
}
}
});

return mySub;
}-*/;

Giuseppe Corti

Please, try to replace

[SYNTAX=JSCRIPT]mySub = new Subscription(subscriptionMode, itemList, fieldList);[/SYNTAX]

with

[SYNTAX=JSCRIPT]mySub = new $wnd.Lightstreamer.Subscription(subscriptionMode, itemList, fieldList);[/SYNTAX]

flybyGWT

Forgot to tell you thanks for catching that missed namespace call.

Giuseppe Corti Please, try to replace

[SYNTAX=JSCRIPT]mySub = new Subscription(subscriptionMode, itemList, fieldList);[/SYNTAX]

with

[SYNTAX=JSCRIPT]mySub = new $wnd.Lightstreamer.Subscription(subscriptionMode, itemList, fieldList);[/SYNTAX]