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  • How should a JEE application store credentials for logging in to an external system?

    - by FGreg
    I am in a situation where I have a Web Application (WAR) that is accessing a REST service provided by another application. The REST service uses Basic HTTP Authentication. So that means the application calling the REST service needs to store user credentials somehow. To further complicate things, this is an enterprise, so there are different 'regions' the application moves through which will have different credentials for the same service (think local development, development region, integration region, user test region, production, etc...) My first instinct is that the credentials should be stored by the JEE container and the application should ask the container for the credentials (probably via JNDI?). I'm beginning to read about Java Authentication and Authorization Service (JAAS) but I'm not sure if that is the appropriate solution to this problem. How should a JEE application store credentials for logging in to an external system? A few more details about my WAR. It is a Spring-Integration project that has no front-end. The container I am working with is Websphere. I am using JEE 5 and Spring 4.0.1. To this point I have not needed to consider spring-security... does this situation mean I should re-evaluate that decision?

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  • Question on methods in Object Oriented Programming

    - by mal
    I’m learning Java at the minute (first language), and as a project I’m looking at developing a simple puzzle game. My question relates to the methods within a class. I have my Block type class; it has its many attributes, set methods, get methods and just plain methods. There are quite a few. Then I have my main board class. At the moment it does most of the logic, positioning of sprites collision detection and then draws the sprites etc... As I am learning to program as much as I’m learning to program games I’m curious to know how much code is typically acceptable within a given method. Is there such thing as having too many methods? All my draw functionality happens in one method, should I break this into a few ‘sub’ methods? My thinking is if I find at a later stage that the for loop I’m using to cycle through the array of sprites searching for collisions in the spriteCollision() method is inefficient I code a new method and just replace the old method calls with the new one, leaving the old code intact. Is it bad practice to have a method that contains one if statement, and place the call for that method in the for loop? I’m very much in the early stages of coding/designing and I need all the help I can get! I find it a little intimidating when people are talking about throwing together a prototype in a day too! Can’t wait until I’m that good!

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  • Unit testing to prove balanced tree

    - by Darrel Hoffman
    I've just built a self-balancing tree (red-black) in Java (language should be irrelevant for this question though), and I'm trying to come up with a good means of testing that it's properly balanced. I've tested all the basic tree operations, but I can't think of a way to test that it is indeed well and truly balanced. I've tried inserting a large dictionary of words, both pre-sorted and un-sorted. With a balanced tree, those should take roughly the same amount of time, but an unbalanced tree would take significantly longer on the already-sorted list. But I don't know how to go about testing for that in any reasonable, reproducible way. (I've tried doing millisecond tests on these, but there's no noticeable difference - probably because my source data is too small.) Is there a better way to be sure that the tree is really balanced? Say, by looking at the tree after it's created and seeing how deep it goes? (That is, without modifying the tree itself by adding a depth field to each node, which is just wasteful if you don't need it for anything other than testing.)

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  • More efficient in range checking

    - by Mob
    I am going to use a specific example in my question, but overall it is pretty general. I use java and libgdx. I have a ship that moves through space. In space there is debris that the ship can tractor beam in and and harvest. Debris is stored in a list, and the object contains it own x and y values. So currently there is no way to to find the debris's location without first looking at the debris object. Now at any given time there can be a huge (1000+) amount of debris in space, and I figure that calculating the distance between the ship and every single piece of debris and comparing it to maximum tractor beam length is rather inefficient. I have thought of dividing space into sectors, and have each sector contain a list of every object in it. This way I could only check nearby sectors. However this essentially doubles memory for the list. (I would reference the same object so it wouldn't double overall. I am not CS major, but I doubt this would be hugely significant.) This also means anytime an object moves it has to calculate which sector it is in, again not a huge problem. I also don't know if I can use some sort of 2D MAP that uses x and y values as keys. But since I am using float locations this sounds more trouble than its worth. I am kind of new to programming games, and I imagined there would be some eloquent solution to this issue.

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  • KC Java Users Group Presentation

    - by rodelljr
    Originally posted on: http://geekswithblogs.net/rodelljr/archive/2014/08/22/kc-java-users-group-presentation.aspxI would like to thank the KC Java Users Group for allowing me to do my presentation; Supporting Multiple Devices Part 2. In this talk, I discussed a Master/Detail application that runs on Android 2.2 devices and forward. I used the Actionbar compat Android library to allow the older devices to have an actionbar. I also used a SQLite database for my data. And just to add one last thing, I also incorporated the use of custom fonts. If you are interesting in looking at this sample application, I have uploaded it to my GitHub account here. I also have a Power Point presentation which you can get here.

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  • What is the most efficient way to add and remove Slick2D sprites?

    - by kirchhoff
    I'm making a game in Java with Slick2D and I want to create planes which shoots: int maxBullets = 40; static int bullet = 0; Missile missile[] = new Missile[maxBullets]; I want to create/move my missiles in the most efficient way, I would appreciate your advise: public void shoot() throws SlickException{ if(bullet<maxBullets){ if(missile[bullet] != null){ missile[bullet].resetLocation(plane.getCenterX(), plane.getCenterY(), plane.image.getRotation()); }else{ missile[bullet] = new Missile("resources/missile.png", plane.getCenterX(), plane.getCenterY(), plane.image.getRotation()); } }else{ bullet = 0; missile[bullet].resetLocation(plane.getCenterX(), plane.getCenterY(), plane.image.getRotation()); } bullet++; } I created the method resetLocation in my Missile class in order to avoid loading again the resource. Is it correct? In the update method I've got this to move all the missiles: if(bullet > 0 && bullet < maxBullets){ float hyp = 0.4f * delta; if(bullet == 1){ missile[0].move(hyp); }else{ for(int x = 0; x<bullet; x++){ missile[x].move(hyp); } } }

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  • Making a class pseudo-immutable by setting a flag

    - by scott_fakename
    I have a java project that involves building some pretty complex objects. There are quite a lot (dozens) of different ones and some of them have a HUGE number of parameters. They also need to be immutable. So I was thinking the builder pattern would work, but it ends up require a lot of boilerplate. Another potential solution I thought of was to make a mutable class, but give it a "frozen" flag, a-la ruby. Here is a simple example: public class EqualRule extends Rule { private boolean frozen; private int target; public EqualRule() { frozen = false; } public void setTarget(int i) { if (frozen) throw new IllegalStateException( "Can't change frozen rule."); target = i; } public int getTarget() { return target; } public void freeze() { frozen = true; } @Override public boolean checkRule(int i) { return (target == i); } } and "Rule" is just an abstract class that has an abstract "checkRule" method. This cuts way down on the number of objects I need to write, while also giving me an object that becomes immutable for all intents and purposes. This kind of act like the object was its own Builder... But not quite. I'm not too excited, however, about having an immutable being disguised as a bean however. So I had two questions: 1. Before I go too far down this path, are there any huge problems that anyone sees right off the bat? For what it's worth, it is planned that this behavior will be well documented... 2. If so, is there a better solution? Thanks

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  • Android Game Development problem whith size and speed

    - by Charlton Santana
    I have been coding speed for an object. I have made it so the object will move from one end of the screen to another at a speed depending on the screen size, at the monemt I have made it so it will take one second to pass the screen. So i have worked out the speed in code but when I go to assign the speed it tells me to force close and i do not understand why. Here is the code: MainGame Code: @Override protected void onDraw(Canvas canvas) { setBlockSpeed(getWidth()); } private int blockSpeed; private void setBlockSpeed(int screenWidth){ Log.d(TAG, "screenWidth " + screenWidth); blockSpeed = screenWidth / 100; // 100 is the FPS.. i want it to take 1 second to pass the screen Math.round(blockSpeed); // to make it a whole number block.speed = blockSpeed; // if i dont put blockSpeed and put eg 8 it still tells me to force close } Block.java Code: public int speed; public void draw(Canvas canvas) { canvas.drawBitmap(bitmap, x - (bitmap.getWidth() / 2), y - (bitmap.getHeight() / 2), null); if(dontmove == 0){ this.x -= speed; } }

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  • Why can't WARs share session info?

    - by rvcoutinho
    I have seen several developers looking for a solution for this problem: accessing session information from a different WAR (even when inside the same EAR) - here are some samples: Any way to share session state between different applications in tomcat?, Access session of another web application, different WAR files, shared resources, Tomcat: How to share data between two applications?, What does the crossContext attribute do in Tomcat? Does it enable session sharing? and so on... From all I have searched, there are some specific solutions depending on the container, but it is somehow 'contrary to the specification'. I have also looked through Java EE specification without any luck on finding an answer. Some developers talk about coupling between web applications, but I tend to disagree. What is the reason one would keep WARs inside the same EAR if not coupling? EJBs, for instance, can be accessed locally (even if inside another EJB JAR within the same EAR). More specifically, one of my WARs handles authentication and authorization, and I would like to share this information with other WARs (in the same EAR). I have managed to work around similar problems before by packaging WARs as JARs and putting them into a singular WAR project (WEB-INF/lib). Yet I do not like this solution (it requires a huge effort on servlet naming and so on). And no solution has answered the first (and most important) question: Why can't WARs share session information?

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  • Should I build a multi-threaded system that handles events from a game and sorts them, independently, into different threads based on priority?

    - by JonathonG
    Can I build a multi-threaded system that handles events from a game and sorts them, independently, into different threads based on priority, and is it a good idea? Here's more info: I am about to begin work on porting a mid-sized game from Flash/AS3 to Java so that I can continue development with multi-threading capabilities. Here's a small bit of background about the game: The game contains numerous asynchronous activities, such as "world updating" (the game environment is constantly changing based on a set of natural laws and forces), procedural generation of terrain, NPCs, quests, items, etc., and on top of that, the effects of all of the player's interactions with his environment are programmatically calculated in real time, based on a set of constantly changing "stats" and once again, natural laws and forces. All of these things going on at once, in an asynchronous manner, seem to lend themselves to multi-threading very well. My question is: Can I build some kind of central engine that handles the "stacking" of all of these events as they are triggered, and dynamically sorts them out amongst the available threads, and would it be a good idea? As an example: Essentially, every time something happens (IE, a magic missile being generated by a spell, or a bunch of plants need to grow to their next stage), instead of just processing that task right then and adding the new object(s) to a list of managed objects, send a reference to that event to a core "event handler" that throws it into a stack of all other currently queued events, which then sorts them out and orders them according to urgency, splits them between a number of available threads for as-fast-as-possible multithreaded execution.

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  • I don't understand how TDD helps me get a good design if I need a design to start testing it

    - by Michael Stum
    I'm trying to wrap my head around TDD, specifically the development part. I've looked at some books, but the ones I found mainly tackle the testing part - the History of NUnit, why testing is good, Red/Green/Refactor and how to create a String Calculator. Good stuff, but that's "just" Unit Testing, not TDD. Specifically, I don't understand how TDD helps me get a good design if I need a Design to start testing it. To illustrate, imagine these 3 requirements: A catalog needs to have a list of products The catalog should remember which products a user viewed Users should be able to search for a product At this points, many books pull a magic rabbit out of a hat and just dive into "Testing the ProductService", but they don't explain how they came to the conclusion that there is a ProductService in the first place. That is the "Development" part in TDD that I'm trying to understand. There needs to be an existing design, but stuff outside of entity-services (that is: There is a Product, so there should be a ProductService) is nowhere to be found (e.g., the second requirement requires me to have some concept of a User, but where would I put the functionality to remind? And is Search a feature of the ProductService or a separate SearchService? How would I know which I should choose?) According to SOLID, I would need a UserService, but if I design a system without TDD, I might end up with a whole bunch of Single-Method Services. Isn't TDD intended to make me discover my design in the first place? I'm a .net developer, but Java resources would also work. I feel that there doesn't seem to be a real sample application or book that deals with a real line of business application. Can someone provide a clear example that illustrates the process of creating a design using TDD?

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  • Who extends interfaces? And why?

    - by Gangnus
    AFAIK, my class extends parent classes and implements interfaces. But I run across a situation, where I can't use implements SomeInterface. It is the declaration of a generic types. For example: public interface CallsForGrow {...} public class GrowingArrayList <T implements CallsForGrow> // BAD, won't work! extends ArrayList<T> Here using implements is syntactically forbidden. I thought first, that using interface inside < is forbidden at all, but no. It is possible, I only have to use extends instead of implements. As a result, I am "extending" an interface. This another example works: public interface CallsForGrow {...} public class GrowingArrayList <T extends CallsForGrow> // this works! extends ArrayList<T> To me it seems as a syntactical inconsistancy. But maybe I don't understand some finesses of Java 6? Are there other places where I should extend interfaces? Should the interface, that I mean to extend, have some special features?

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  • Multiple vulnerabilities fixed in Java 7U9

    - by RitwikGhoshal
    CVE DescriptionCVSSv2 Base ScoreComponentProduct and Resolution CVE-2012-5086 10.0 Java 7 Solaris 11.1 10/12 SRU 2.5 CVE-2012-5083 10.0 CVE-2012-5087 10.0 CVE-2012-1533 10.0 CVE-2012-1532 10.0 CVE-2012-1531 10.0 CVE-2012-5076 10.0 CVE-2012-3143 10.0 CVE-2012-5088 10.0 CVE-2012-5089 7.6 CVE-2012-5084 7.6 CVE-2012-3159 7.5 CVE-2012-5068 7.5 CVE-2012-4416 6.4 CVE-2012-5074 6.4 CVE-2012-5071 6.4 CVE-2012-5069 5.8 CVE-2012-5067 5.0 CVE-2012-5070 5.0 CVE-2012-5075 5.0 CVE-2012-5073 5.0 CVE-2012-5079 5.0 CVE-2012-5072 5.0 CVE-2012-5081 5.0 CVE-2012-3216 2.6 CVE-2012-5077 2.6 CVE-2012-5085 0.0 This notification describes vulnerabilities fixed in third-party components that are included in Oracle's product distributions. Information about each CVE can be found on Java SE Critical Patch Update - October 2012 Information about vulnerabilities affecting Oracle products can be found on Oracle Critical Patch Updates and Security Alerts page.

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  • 16-bit PNGs in Slick2D

    - by Neglected
    I'm working on a project and I'm using some 3rd party sprites just to get it off the ground; recently I've come into a hitch. Slick2D doesn't seem to want to load my images. That is, it will warn me that images are the wrong bit-depth. All the images are in 16-bit PNG form (PNG is required for transparency). Is there any way I can disable the warning (being the bad guy programmer (the console print for each individual load REALLY SLOWS DOWN the image)) or is there another solution? I was thinking about converting all images (using imagemagick) to .gif (with an alpha channel). Would there be any loss in quality between formats? EDIT: I tried using imagemagick but some of the sprites use pure black so I can't do that without wrecking the image. EDIT2: using "identify" on any of the images show them as being 8-bit.. but Slick2D won't load them. What the hell? D: EDIT3: Issue solved (ish). If you are googling this then just disable the java png loader from slick by sticking this somewhere in your code (like the main method): System.setProperty("org.newdawn.slick.pngloader", "false");

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  • What is involved with writing a lobby server?

    - by Kira
    So I'm writing a Chess matchmaking system based on a Lobby view with gaming rooms, general chat etc. So far I have a working prototype but I have big doubts regarding some things I did with the server. Writing a gaming lobby server is a new programming experience to me and so I don't have a clear nor precise programming model for it. I also couldn't find a paper that describes how it should work. I ordered "Java Network Programming 3rd edition" from Amazon and still waiting for shipment, hopefully I'll find some useful examples/information in this book. Meanwhile, I'd like to gather your opinions and see how you would handle some things so I can learn how to write a server correctly. Here are a few questions off the top of my head: (may be more will come) First, let's define what a server does. It's primary functionality is to hold TCP connections with clients, listen to the events they generate and dispatch them to the other players. But is there more to it than that? Should I use one thread per client? If so, 300 clients = 300 threads. Isn't that too much? What hardware is needed to support that? And how much bandwidth does a lobby consume then approx? What kind of data structure should be used to hold the clients' sockets? How do you protect it from concurrent modification (eg. a player enters or exists the lobby) when iterating through it to dispatch an event without hurting throughput? Is ConcurrentHashMap the correct answer here, or are there some techniques I should know? When a user enters the lobby, what mechanism would you use to transfer the state of the lobby to him? And while this is happening, where do the other events bubble up? Screenshot : http://imageshack.us/photo/my-images/695/sansrewyh.png/

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  • Quaternions, Axis Angles and Rotation Matrices. Which of these should I use for FP Camera?

    - by Afonso Lage
    After 2 weeks of reading many math formulas and such I know what is a Quaternion, an Axis Angles and Matrices. I have made my own math libary (Java) to use on my game (LWJGL). But I'm really confused about all this. I want to have a 3D first person camera. The move (translation) is working fine but the rotation isnt working like I need. I need a camera to rotate arround world Axis and not about its own axis. But even using Quaternions, this doesnt work and no matter how much I read about Euler Angles, everybody says to me dont touch on it! This is a little piece of code that i'm using to make the rotation: Quaternion qPitch = Quaternion.createFromAxis(cameraRotate.x, 1.0f, 0.0f, 0.0f); Quaternion qYaw = Quaternion.createFromAxis(cameraRotate.y, 0.0f, 1.0f, 0.0f); this.multiplicate(qPitch.toMatrix4f().toArray()); this.multiplicate(qYaw.toMatrix4f().toArray()); Where this is a Matrix4f view matrix and cameraRotate is a Vector3f that just handle the angles to rotate obtained from mouse move. So I think I'm doing everything right: Translate the view Matrix Rotate the Move Matrix So, after reading all this, I just want to know: To obtain a correct first person camera rotate, I must need to use Quaternios to make the rotations, but how to rotate around world axis? Thanks for reading it. Best regards, Afonso Lage

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  • Sprite batching in OpenGL

    - by Roy T.
    I've got a JAVA based game with an OpenGL rendering front that is drawing a large amount of sprites every frame (during testing it peaked at 700). Now this game is completely unoptimized. There is no spatial partitioning (so a sprite is drawn even if it isn't on screen) and every sprite is drawn separately like this: graphics.glPushMatrix(); { graphics.glTranslated(x, y, 0.0); graphics.glRotated(degrees, 0, 0, 1); graphics.glBegin(GL2.GL_QUADS); graphics.glTexCoord2f (1.0f, 0.0f); graphics.glVertex2d(half_size , half_size); // upper right // same for upper left, lower left, lower right graphics.glEnd(); } graphics.glPopMatrix(); Currently the game is running at +-25FPS and is CPU bound. I would like to improve performance by adding spatial partitioning (which I know how to do) and sprite batching. Not drawing sprites that aren't on screen will help a lot, however since players can zoom out it won't help enough, hence the need for batching. However sprite batching in OpenGL is a bit of mystery to me. I usually work with XNA where a few classes to do this are built in. But in OpenGL I don't know what to do. As for further optimization, the game I'm working on as a few interesting characteristics. A lot of sprites have the same texture and all the sprites are square. Maybe these characteristics will help determine an efficient batching technique?

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