wffweb - Java Developers Guide

Lossless browser page communication in wffweb-12

It is available since 12.0.0. It is enabled by default. If it is enabled this is what happens, let's understand it by an example:

//some existing div in the UI
Div mainDiv = new Div(null);

Div div1 = new Div(null);			
// step 1
mainDiv.appendChild(div1);        


Div div2 = new Div(null);			
// step 2
mainDiv.appendChild(div2);


Div div3 = new Div(null);
// step 3
div2.replaceWith(div3);					

Suppose, the client received UI changes for the step 1 and suddenly the network lost, the changes for step 2 was already sent from the server but could not be delivered to the client. The network reconnected and the client received changes for step 3. The changes for step 3 and subsequent changes will be ignored because the changes for step 3 is not valid as the changes for step 2 is not applied on the UI, precisely div2 is not available on the UI so it cannot be replaced with div3 . After step 1, the client will execute the JavaScript code set in BrowserPage.Settings.onPayloadLoss.javaScript . The default value for the JavaScript is for reloading the browser page so the browser page will reload just after executing step 1. This is what happens when client loses a payload sent from the server.

The same scenario is applicable at server side. Suppose, there are three buttons on the UI, button1 button2 and button3. Each button has an OnClick event attribute java code. The user clicked on button1 and button2, the OnClick event attribute of button1 is executed at server side but the event changes for button2 could not be delivered to the server due to network failure. The network reconnected, the user clicks on button3 and the onclick event changes are delivered to the server but the OnClick event of button3 will not be executed as the previous payload was not delivered to server, i.e. the payload of button3 event and subsequent events will not be processed instead it will execute the action set in BrowserPage.Settings.onPayloadLoss.serverSideAction (just after executing OnClick of button1). The default BrowserPage.Settings.onPayloadLoss.serverSideAction is for reloading the browser page.

The browserPage.defaultSettings() can be used to get the default setting of the BrowserPage instance. To change the current Settings override useSettings method in the subclass of BrowserPage. getSettings may be used to get the current settings (i.e. the applied settings by useSettings method).

Eg:-

@Override
protected Settings useSettings() {
    final OnPayloadLoss onPayloadLoss = new OnPayloadLoss(
            "console.log('reloading page');location.reload();",
            defaultSettings().onPayloadLoss().serverSideAction());
    
    final Settings newSettings =  new Settings(
            defaultSettings().inputBufferLimit(), defaultSettings().inputBufferTimeout(),
            defaultSettings().outputBufferLimit(), defaultSettings().outputBufferTimeout(),
            onPayloadLoss);
    return newSettings;
}

To disable this lossless browser page communication, pass null for BrowserPage.Settings.onPayloadLoss

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