Passive view for Ext GWT applications

Seeing “Google Web Toolkit Architecture: Best Practices For Architecting Your GWT App” presentation by Ray Ryan coincided with the start of a new project – an Ext GWT front-end application for one of our clients. We liked the idea of testing front-end code entirely in JRE so we decided to give the model view presenter approach to building front-ends a try. Unfortunately, GXT widgets come with no fine-grained interfaces like GWT’s HasValue. Our display interfaces quickly ended up returning GXT widgets – hard to mock or even not possible to instantiate in JRE due to JSNI. We had to come up with a solution and do it fast. Technical debt had been registered on the project backlog and in a couple of days we had an opportunity to work on this. We developed several simple interfaces that let us compose display interfaces using this common vocabulary and factory class that returns implementations for standard GXT widgets. It is good to think about returned implementations as gateways that provide simple API whose implementation can be easily substituted by some test double. It’s better to look at some actual code, this should make everything more clear. The first of the interfaces is HasValue:

public interface HasValue {
    T getValue();
    void setValue(T value);

we have others – for selection, clicking, double clicking …

public interface HasSelected {
    public static interface Handler {
        void onSelected();
    public void addHandler(Handler h);

Corresponding factory methods …

public static HasValue createHasValue(final Label label) {
    return new HasValue() {
        public void setValue(String value) {

        public String getValue() {
            return label.getText();
public static HasSelected createHasSelected(final Button button) {
    return new HasSelected() {

        public void addHandler(final Handler handler) {
            button.addSelectionListener(new SelectionListener() {

                public void componentSelected(ButtonEvent ce) {

Now it is easy to build Display interfaces:

public class MyPresenter {

    public static interface Display {

        HasSelected getMyButtonSelected();

        HasValue getName();


and their implementations:

public HasSelected getMyButtonSelected() {
    return DisplayMemberFactory.createHasSelected(myButton);


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Super Confitura Man

How Super Confitura Man came to be :)

Recently at TouK we had a one-day hackathon. There was no main theme for it, you just could post a project idea, gather people around it and hack on that idea for a whole day - drinks and pizza included.

My main idea was to create something that could be fun to build and be useful somehow to others. I’d figured out that since Confitura was just around a corner I could make a game, that would be playable at TouK’s booth at the conference venue. This idea seemed good enough to attract Rafał Nowak @RNowak3 and Marcin Jasion @marcinjasion - two TouK employees, that with me formed a team for the hackathon.

Confitura 01

The initial plan was to develop a simple mario-style game, with preceduraly generated levels, random collectible items and enemies. One of the ideas was to introduce Confitura Man as the main character, but due to time constraints, this fall through. We’ve decided to just choose a random available sprite for a character - hence the onion man :)

Confitura 02

How the game is played?

Since we wanted to have a scoreboard and have unique users, we’ve printed out QR codes. A person that would like to play the game could pick up a QR code, show it against a camera attached to the play booth. The start page scanned the QR code and launched the game with username read from paper code.

The rest of the game was playable with gamepad or keyboard.

Confitura game screen


Writing a game takes a lot of time and effort. We wanted to deliver, so we’ve decided to spend some time in the days before the hackathon just to bootstrap the technology stack of our enterprise.

We’ve decided that the game would be written in some Javascript based engine, with Google Chrome as a web platform. There are a lot of HTML5 game engines - list of html5 game engines and you could easily create a game with each and every of them. We’ve decided to use Phaser IO which handles a lot of difficult, game-related stuff on its own. So, we didn’t have to worry about physics, loading and storing assets, animations, object collisions, controls input/output. Go see for yourself, it is really nice and easy to use.

Scoreboard would be a rip-off from JIRA Survivor with stats being served from some web server app. To make things harder, the backend server was written in Clojure. With no experience in that language in the team, it was a bit risky, but the tasks of the server were trivial, so if all that clojure effort failed, it could be rewritten in something we know.


During the whole Confitura day there were 69 unique players (69 QR codes were used), and 1237 games were played. The final score looked like this:

  1. Barister Lingerie 158 - 1450 points
  2. Boilerdang Custardbath 386 - 1060 points
  3. Benadryl Clarytin 306 - 870 points

And the obligatory scoreboard screenshot:

Confitura 03


The game, being created in just one day, had to have problems :) It wasn’t play tested enough, there were some rough edges. During the day we had to make a few fixes:

  • the server did not respect the highest score by specific user, it was just overwritting a user’s score with it’s latest one,
  • there was one feature not supported on keyboard, that was available on gamepad - turbo button
  • server was opening a database connection each time it got a request, so after around 5 minutes it would exhaust open file limit for MongoDB (backend database), this was easily fixed - thou the fix is a bit hackish :)

These were easily identified and fixed. Unfortunately there were issues that we were unable to fix while the event was on:

  • google chrome kept asking for the permission to use webcam - this was very annoying, and all the info found on the web did not work - StackOverflow thread
  • it was hard to start the game with QR code - either the codes were too small, or the lighting around that area was inappropriate - I think this issue could be fixed by printing larger codes,

Technology evaluation

All in all we were pretty happy with the chosen stack. Phaser was easy to use and left us with just the fun parts of the game creation process. Finding the right graphics with appropriate licensing was rather hard. We didn’t have enough time to polish all the visual aspects of the game before Confitura.

Writing a server in clojure was the most challenging part, with all the new syntax and new libraries. There were tasks, trivial in java/scala, but hard in Clojure - at least for a whimpy beginners :) Nevertheless Clojure seems like a really handy tool and I’d like to dive deeper into its ecosystem.

Source code

All of the sources for the game can be found here TouK/confitura-man.

The repository is split into two parts:

  • game - HTML5 game
  • server - clojure based backend server

To run the server you need to have a local MongoDB installation. Than in server’s directory run: $ lein ring server-headless This will start a server on http://localhost:3000

To run the game you need to install dependencies with bower and than run $ grunt from game’s directory.

To launch the QR reading part of the game, you enter http://localhost:9000/start.html. After scanning the code you’ll be redirected to http://localhost:9000/index.html - and the game starts.


Summing up, it was a great experience creating the game. It was fun to watch people playing the game. And even with all those glitches and stupid graphics, there were people vigorously playing it, which was awesome.

Thanks to Rafał and Michał for great coding experience, and thanks to all the players of our stupid little game. If you’d like to ask me about anything - feel free to contact me by mail or twitter @zygm0nt

Recently at TouK we had a one-day hackathon. There was no main theme for it, you just could post a project idea, gather people around it and hack on that idea for a whole day - drinks and pizza included.

My main idea was to create something that could be fun to build and be useful somehow to others. I’d figured out that since Confitura was just around a corner I could make a game, that would be playable at TouK’s booth at the conference venue. This idea seemed good enough to attract >Conclusion

Phonegap / Cordova and cross domain ssl request problem on android.

In one app I have participated, there was a use case:
  • User fill up a form.
  • User submit the form.
  • System send data via https to server and show a response.
During development there wasn’t any problem, but when we were going to release production version then some unsuspected situation occurred. I prepare the production version accordingly with standard flow for Android environment:
  • ant release
  • align
  • signing
During conduct tests on that version, every time I try to submit the form, a connection error appear. In that situation, at the first you should check whitelist in cordova settings. Every URL you want to connect to, must be explicit type in:
If whitelist looks fine, the error is most likely caused by inner implementation of Android System. The Android WebView does not allow by default self-signed SSL certs. When app is debug-signed the SSL error is ignored, but if app is release-signed connection to untrusted services is blocked.


You have to remember that secure connection to service with self-signed certificate is risky and unrecommended. But if you know what you are doing there is some workaround of the security problem. Behavior of method
must be changed.

Thus add new class extended CordovaWebViewClient and override ‘onReceivedSslError’. I strongly suggest to implement custom onReceiveSslError as secure as possible. I know that the problem occours when app try connect to and in spite of self signed certificate the domain is trusted, so only for that case the SslError is ignored.

public class MyWebViewClient extends CordovaWebViewClient {

   private static final String TAG = MyWebViewClient.class.getName();
   private static final String AVAILABLE_SLL_CN
= "";

   public MyWebViewClient(DroidGap ctx) {

   public void onReceivedSslError(WebView view,
SslErrorHandler handler, error) {

String errorSourceCName = error.getCertificate().

       if( AVAILABLE_SLL_CN.equals(errorSourceCName) ) {
           Log.i(TAG, "Detect ssl connection error: " +
error.toString() +
„ so the error is ignored”);


       super.onReceivedSslError(view, handler, error);
Next step is forcing yours app to  use custom implementation of WebViewClient.

public class Start extends DroidGap
   private static final String TAG = Start.class.getName();

   public void onCreate(Bundle savedInstanceState)
       super.setIntegerProperty("splashscreen", R.drawable.splash);

       MyWebViewClient myWebViewClient = new MyWebViewClient(this);

// yours code

That is all ypu have to do if minSdk of yours app is greater or equals 8. In older version of Android there is no class
So in class MyCordovaWebViewClient class there are errors because compliator doesn’t see SslError class. Fortunately Android is(was) open source, so it is easy to find source of the class. There is no inpediments to ‘upgrade’ app and just add the file to project. I suggest to keep original packages. Thus after all operations the source tree looks like:

Class SslError placed in source tree. 
 Now the app created in release mode can connect via https to services with self-signed SSl certificates.