In a previous post we talked about Java Games deployment options, in this post we want to talk about one custom solution provided by the LWJGL: the LWJGL Applet Loader.

The LWJGL Applet Loader is an Applet which performs a lot of common deployment tasks:

  • It shows a nice and customizable loading screen when deployment is being processed, with detailed messages for each task: downloading file.jar, extracting file.jar.gz, etc.
  • It downloads all required dependencies. If they are compressed using gzip, LZMA or Pack200, it extracts them.
  • It has a cache for all your dependencies so if one dependency is not modified on the server, then it is not downloaded again.
  • It configures the Java library path to load all your native dependencies.
  • Finally, it runs your game’s applet.

A feature in mind when developing the LWJGL Applet Loader is that it should start as fast as possible, for that, the jar of the Applet Loader should be really small. The idea is to speed up all the Java loading screen so it can show quickly your custom loading screen.

It provides a lot of parameters in order to let you customize deployment stuff, like which natives dependencies you need for a specific platform, the logo and progress bar, etc. Full documentation of the parameters is on the API docs and you also have a great tutorial at LWJGL Wiki.

This is how it looks when loading an Applet using the LWJGL Applet Loader with the default loading screen:

note: Even without customization, it looks much nicer than Java default loading screen.


  • It lets you customize loading screen, and create Applet using natives support in an easy way.
  • It starts fast. This avoids some browser freeze bug when starting a Java Applet, like Firefox on Linux platforms.
  • It handles different compression options like gzip and LZMA, it also handles Pack200 jars.
  • It works on Mac OS, that is a big difference versus running New Generation Plug-In Java Applets, because they are disabled on Mac OS.
  • It is open source and the guys maintaining it are always open to receive patches and improvement ideas.


  • Pack200 and compression stuff is not done automatically, you have to specify exactly which file you want to download (example: you have to specify that you want to download somedependency.jar.pack.gz instead of having the Applet Loader to detect automatically which version to download by receiving the content encoding from the server).
  • Assumes you need native dependencies, so you need to fill some Applet parameters even if you don’t need them. (we want to add an RFE for that)
  • It doesn’t use the same cache other Java Applets or Java Web Start use. That means you have to download twice one Applet distributed using LWJGL Applet loader and Java Web Start, and it will cost you double space.

To see LWJGL Applet Loader working you can try one of our games here (warning: link could be broken in the future) or you can try a working and stable version of a game using LWJGL Applet Loader here, its name is Minecraft, don’t know if you know about it.

In one of the next posts we want to talk in detail about another deployment option we mentioned before, now that we have some experience using it: getdown.


  • Bug #288642 in sun-java6 - Java Applets freeze Firefox -

  • Following our Games as Applets series, we want to talk about the Wordrpess Page Template we are using in order to deploy our games as Java Applets inside the Blog.

    WordPress Custom Fields

    When creating a new blog post or page, the creator can add metadata using WordPress Custom Fields, to be processed later by the PHP templates associated. In our case, we are using the following custom fields:

    • applet_height - height of the applet.
    • applet_width - width of the applet.
    • applet_screenshot - URL to a screenshot of the game
    • jnlp_url - URL to the JNLP for launching the game.

    WordPress Page Templates

    After adding metadata to our posts or pages, we need to make a WordPress Page Template in order to process it. In our case, we created a PHP template for our games deployed as Java Applets using the structure explained in our last post about Games as Applets. Our games template looks like this file.

    Note: I didn’t want to put all the PHP file code directly in the post because it is too large.

    This is how we get the post metadata:

    	$jnlp_href = get_post_meta($post->ID, "jnlp_url", true);
    	$applet_width = get_post_meta($post->ID, "applet_width", true); 
    	$applet_height = get_post_meta($post->ID, "applet_height", true);  
    	$applet_screenshot = get_post_meta($post->ID, "applet_screenshot", true);  

    And this is how we pass the values to the javascript:

    <?php echo '
    ' ?>

    Once the page template is created, if we want to add a new page for a game, we only have to select it from the templates list and voilá.


    Using WordPress Page Templates and Custom Fields, we can reduce the information of the game’s page to game’s related information only, and move all common logic and information between game pages to the page template.

    This is how it looks to edit a game page:
    Game Page being Edited

    Note: there is no applet tag or javascript in the page.

    Also, if we modify the page template, we have all game pages updated, that could be really useful if you need to fix a bug or make an improvement to the page but could be a problem in case we introduce a new bug.

    One problem not resolved yet is if you want to change the WordPress Theme, you will have to migrate the page template. I don’t know exactly if you can create a page template theme independent.


    When you develop Java games for PC, you have different ways to deploy them. We want to talk a bit about some of them.


    The user has to download the game to run it on his machine, probably it comes with an installer to install the game before he can play it.


    • The game can be played offline when it has no online requirements.
    • User knows where the game is installed and sometimes decides where he wants to install it. They also can uninstall the game.
    • It is the only way to deploy a game in portals like Steam, Altitude Game is an example of that.


    • Users have to download a patch each time there is a new version. As a developer, you can implement something to download patches and apply them.
    • As a developer, you have to implement an installer. Also, you have to make different installers for each platform, an example of that is Revenge of the Titans (ROTT) from Puppy Games.
    • You have to create patches and deploy new files to be downloaded each time you have a new version of the game after a bug fix or new feature. Else, you force people to download large files each time you have an updated version.
    • Java Runtime Environment (JRE) must be installed or you have to embed JRE with your game. In the second case, your game file becomes bigger, for larger games that is not a problem but for small games embedded JRE could be, for example, 300% of the game size (at today, JRE weight is about 20MB). Even though there could be a JRE installed, being able to execute your program directly depends on a good configuration of the JRE within the OS. To solve that, developers usually generate a native wrapper that detects where the installed JRE is, and if it is not installed prompts the user to download one, or reports the error to the user.


    Java Applets works inside the browser, as well as other web technologies like Flash and Unity. Users only have to open a page with a Java Applet inside and it is loaded by the web browser. Minecraft is an example of a successful Java Applet Game (it has other deployment options as well).


    • Users only have to follow a link to play the game. No game install is required.
    • Users are always playing the latest game version, because it is being downloaded from the server.
    • As other web technologies, you can add information or even ads to your applet page without having to put that inside the game.
    • Java Applets are as powerful as a Java Desktop application.
    • New Generation Java Applets accepts Java Networking Launching Protocol (JNLP) files (more info on next blog posts).
    • Pack200 and GZip compression support to reduce jar download sizes (only using plugin2).


    • JRE must be installed on the client machine. However, nowadays you can assume the required plugin is installed on most of the client machines.
    • You need a web server to deploy your game jars or you have to use a games portal like GameJolt or Games4j.
    • Dependning on the Java Applet technology you are using (plugin2, etc), firefox can freeze when the applet is loading, or could not work on Mac OS (more information on next blog posts).
    • As a developer, you need to sign your jars with a certificate if you want to have full access (to do extra stuff like writing a configuration file on user’s home folder).
    • If you ask for full access, a security dialog box is displayed. It tends to scare users, if you have a valid certificate then it is a bit less scary.

    Web Start

    Java Web Start is some kind of mixing between the last two. As developer you use a JNLP file to describe which resources must be downloaded. Users only have to click on a JNLP link and then the game is opened automatically by Java Web Start.


    • Users only have to follow a link to play the game. No game install is required.
    • Automatically downloads the latest version of your game from the server each time the user wants to play a game.
    • It has a cache for downloaded resources, so if you only update one jar then it is the only one downloaded by the user’s machine the next time the user opens the game.
    • As a developer you can specify to run the game offline.
    • It has a clean way to specify your game’s resources using the JNLP file.
    • Pack200 and GZip compression support to reduce jar download sizes.


    • Some browsers are not configured correctly (for example, Google Chrome) and they don’t open the JNLP automatically using Java Webstart, they just download the file.
    • Same thing with certificates and signing as the Java Applet.
    • As a developer you need a web server to put all your game’s resources, we don’t know any portal which accepts JNLP games yet.
    • Java Webstart Cache and Log files are difficult to find on user’s machine.


    Getdown is a custom solution made by Three Rings in order to replace Java Web Start technology due to its limitations, as it is explained on Getdown’s project Wiki. We lack experience and information about this solution, so the pros/cons section could be a bit empty.


    • Open source, that means you know what is happening, and you can collaborate, something impossible with Java Web Start.
    • Working examples of mmo games like Sprial Knights from Three Rigns and Tribal Trouble 2 from Oddlabs.


    • It is custom made. That means, as a developer you have to be aware that if something goes wrong you may have no support (note the conditional). But can’t say it is really a cons because with Java Web Start you don’t have any support at all from Oracle’s team.


    1. Altitude Game -
    2. GameJolt -
    3. Games4j -
    4. Getdown -
    5. Java Plug-In Technology -
    6. Minecraft -
    7. Oddlabs -
    8. Pack200 -
    9. Puppy Games -
    10. Revenge of the Titans -
    11. Sprial Knights -
    12. Steam -
    13. Three Rings -
    14. LWJGL Wiki -

    UPDATE: added link to LWJGL wiki page about how to distribute LWJGL Java Applications (most of them applies for Java Applications in general)

    Talking with kappaOne, one of the LWJGL developers, he pointed us that our applet solution has one problem. When js is disabled or it has failed to load, then the applet tag is not written, then the game is not loaded.

    In order to fix this problem, we adopted part of his solution. He always creates the applet tag for the game and then hides it using js. If for some reason js fails, then the applet starts automatically.

    The new html needed looks like this:


    <div id="applet" class="applet" align="center">
    	<applet id="gameApplet" width="800" height="600" code="" archive="">
    		<param name="jnlp_href" value="" >

    And this is the modified js with a merge between his solution and ours:


    var width="800";
    var height="600";
    var jnlp_href="";
    var screenshotUrl="/wp-content/uploads/2010/12/zombierockers-screenshot01.jpg";
    var appletTag;
    var requiredVersion = '1.6.0_10+'
    var attributes = { code:'',  width:width, height:height} ; 
    var parameters = {jnlp_href: jnlp_href}; 
    function hideApplet(){
    	var appletbox=document.getElementById('applet');
    		appletTag = appletbox.innerHTML;
    	if (navigator.appName == 'Microsoft Internet Explorer') {
    		var params = "";
    		var p = appletbox.getElementsByTagName("PARAM");
    		for(var i=0; i < p.length; i++) {
    			params += p[i].outerHTML;
    		appletTag = appletTag.replace("<&#47APPLET>", params+"<&#47APPLET>");
    	var isRequiredVersion = deployJava.versionCheck(requiredVersion);
    	var text = ""
    	var callback = ""
    	if (isRequiredVersion) {
    		text = "Click to play"
    		callback = "showApplet()"
    	} else {
    		text = "You don't have java plugin enabled, click to install"
    		callback = "installJava(\'" + requiredVersion + "\')"
    	// adds the screenshot inside the applet div
    	var screenshotDivHtml = "<div id=\"screenshot\" class=\"play\" onclick=\""+callback+"\" style=\"width:"+width+"px; height:"+height+"px;\">";
    	screenshotDivHtml += "<span>"+text+"<&#47span>";
    	screenshotDivHtml += "<img id=\"screenshotImage\" src=\""+screenshotUrl+"\" alt=\""+text+"\" width=\""+width+"px\" height=\""+height+"px\">"+"<&#47img>";
    	screenshotDivHtml += "<&#47div>";
    function showApplet(){
    	var appletbox=document.getElementById('applet');
    	appletbox.innerHTML = appletTag;
    function installJava(version) { 

    You can see a working example here.

    Thats all.

    Well, Ludum Dare 19 is finished, obviously Discover the Way didn’t won any category, but at least we have some feedback.

    The game made position 58 of 133, this is its rating:

    Inn Fun The Gra Aud Hum Ove Com
    3 3 3 4 2 - 3 -
    2 3 2 3 2 2 3 5
    4 3 2 3 2 2 3 3
    3 3 2 3 3 - 3 3
    2 1 1 3 1 1 2 -
    3 4 5 3 - 2 4 5
    2 2 2 3 2 1 2 -
    2 3 2 4 2 1 3 4
    3 3 1 3 3 - 3 3
    4 5 3 4 3 1 4 3
    2 2 1 3 3 - 3 3
    3 3 2 3 2 2 3 2
    3 3 2 3 3 - 3 3
    3 1 1 3 2 - 2 2
    3 3 3 3 2 - 3 4
    4 2 4 4 4 - 3 4
    2.88 2.75 2.25 3.25 2.40 1.50 2.94 3.38

    Follow the link to the game page at the contest if you want to see users comments, remember though that people rated the first version which was not polished nor balanced enough.

    Here you can see all Ludum Dare 19 results.

    Some final thoughts:

    First of all, I really liked the idea of the game, but on the other hand I knew it wasn’t going to win. However, I believe I made some mistakes that made the game have a worse rating.

    The first mistake was the name, I named the game Discover the Name because I had no game by that moment, I was deciding what to do and though it was a funny name. After realizing the main objective was to discover a safe path between two points, then I thought to change the name to Discover the Way or Discover the Path, to give the player an idea of what he has to do, but I didn’t. That caused confusion to the players because they were expecting they have to discover a hidden name, not a hidden path.

    Another mistake was to be to lazy to make some balance to the game before the contest ends, I finished the game about 2hs before but I was tired so I entered that version. The day after, I took less than 1hr to balance it a bit, and the game changed a lot, it became more playable and it gave more importance to the main objective because the player couldn’t take shortcuts to the targets any more, he has to discover a safe path, that is the real relation to the contest Theme (Discovery).

    The third mistake, less important than the others was to remove the gameplay video from the game’s page. The game’s entry allow contestants to put only 5 links. At fist I put a link to the game, to the source code, a link to our blog, a link to the a gameplay video and a link to the jam version of the game, but after I uploaded the timelapse video to youtube I had to remove one of the links and the gameplay video seemed to be the best choice because I had a link to it inside our blog. That was a mistake because new players watched the gameplay video to see what they have to do in the game, it was some kind of tutorial, without it players felt disoriented.

    I made a short postmortem at Ludum Dare’s blog, follow the link if you want to read it.

    That’s all, thanks for reading.

    UPDATE: added game position and updated link to Ludum Dare 19 results in order.