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  • MVC: How to Implement Linked Views?

    - by cw'
    I'm developing a java application to visualize time series. I need (at least) three linked views, meaning that interaction with one of them updates the others. The views are: A list represents the available and currently selected time series. The selected time series are used as input for subsequent computations. Changing the selection should update the other views. A line chart displays the available and selected time series. Time series should be selectable from here by clicking on them. A bar chart shows aggregated data on time series. When zooming in to a period of time, the line chart should zoom in to the same period (and vice versa). How to implement this nicely, from a software engineering point of view? I.e. I'd like to write reusable and clear, maintainable code. So I thought of the MVC pattern. At first I liked the idea of having the three view components observing my model class and to refresh views upon being notified. But then, it didn't feel right to store view related data in the model. Storing e.g. the time series selection or plot zoom level in the model makes implications about the view which I wouldn't want in a reusable model. On the other hand, having the controllers observe each other results in a lot of dependencies. When adding another view, I'd have to register all other views as observer of the new view and vice versa, passing around many references and introducing dependencies. Maybe another "model" storing only view-related data would be the solution?

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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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  • [WebLogic, Java] WebLogic Developer/Production Web Profile, Full Java EE 6 Platform - Chat Transcript and Slides from OTN Virtual Developer Day

    - by yosuke.arai(at)oracle.com
    ????????????????????????WebLogic Server Virtual Developer Days??JavaEE6???????QA???????????????????(FireFox???????????????????????????????????????) ?????????????????????????????! > Q1) WLS10.3.4??JavaEE6????????????? > Q4) Java EE6 ???????IDE????????? > Q12) Jdeveloper?Java EE 6?????????????? > Q26) managed beans?EJB????????????????EJB??????????????????????managed beans?????????????????????Managed Beans?????????? > Q29) XML???????????????????????????????

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  • Updating the jump in game

    - by Luka Tiger
    I am making a Java game and I want my game to run the same on any FPS so I'm using time delta between each update. This is the update method of the Player: public void update(long timeDelta) { //speed is the movement speed of a player on X axis //timeDelta is expressed in nano seconds so I'm dividing it with 1000000000 to express it in seconds if (Input.keyDown(37)) this.velocityX -= speed * (timeDelta / 1000000000.0); if (Input.keyDown(39)) this.velocityX += speed * (timeDelta / 1000000000.0); if(Input.keyPressed(38)) { this.velocityY -= 6; } velocityY += g * (timeDelta/1000000000.0); //applying gravity move(velocityX, velocityY); /*this is method which moves a player according to velocityX and velocityY, and checking the collision */ this.velocityX = 0.0; } The strange thing is that when I have unlimited FPS (and update number) my player is jumping about 10 blocks. It jumps even higher when the FPS is increasing. If I limit FPS it is jumping 4 blocks. (BLOCK: 32x32) I have just realized that the problem is this: if(Input.keyPressed(38)) { this.velocityY -= 6; } I add -6 to velocityY which increases player's Y proportionally to the update number and not to the time. But I don't know how to fix this.

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  • How do you take into account usability and user requirements for your application?

    - by voroninp
    Our team supports BackOffice application: a mix of WinForm and WPF windows. (about 80 including dialogs). Really a kind of a Swiss Army Knife. It is used by developers, tech writers, security developers, testers. The requirements for new features come quite often and sometimes we play Wizard of Oz to decide which GUI our users like the most. And it usually happens (I admit it can be just my subjective interpretation of the reality) that one tiny detail giving the flavor of good usability to our app requires a lot of time. This time is being spent on 'fighting' with GUI framework making it act like we need. And it very difficult to make estimations for this type of tasks (at least for me and most members of our team). Scrum poker is not a help either. Management often considers this usability perfectionism to be a waste of time. On the other hand an accumulated affect of features where each has some little usability flaw frustrates users. But the same users want frequent releases and instant bug fixes. Hence, no way to get the positive feedback: there is always somebody who is snuffy. I constantly feel myself as competing with ourselves: more features - more bugs/tasks/architecture. We are trying to outrun the cart we are pushing. New technologies arrive and some of them can potentially help to improve the design or decrease task implementation time but these technologies require learning, prototyping and so on. Well, that was a story. And now is the question: How do you balance between time pressure, product quality, users and management satisfaction? When and how do you decide to leave the problem with not a perfect but to some extent acceptable solution, how often do you make these decisions? How do you do with your own satisfaction? What are your priorities? P.S. Please keep in mind, we are a BackOffice team, we have neither dedicated technical writer nor GUI designer. The tester have joined us recently. We've much work to do and much freedom concerning 'how'. I like it because it fosters creativity but I don't want to become too nerdy perfectionist.

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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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  • Should library classes be wrapped before using them in unit testing?

    - by Songo
    I'm doing unit testing and in one of my classes I need to send a mail from one of the methods, so using constructor injection I inject an instance of Zend_Mail class which is in Zend framework. Example: class Logger{ private $mailer; function __construct(Zend_Mail $mail){ $this->mail=$mail; } function toBeTestedFunction(){ //Some code $this->mail->setTo('some value'); $this->mail->setSubject('some value'); $this->mail->setBody('some value'); $this->mail->send(); //Some } } However, Unit testing demands that I test one component at a time, so I need to mock the Zend_Mail class. In addition I'm violating the Dependency Inversion principle as my Logger class now depends on concretion not abstraction. Does that mean that I can never use a library class directly and must always wrap it in a class of my own? Example: interface Mailer{ public function setTo($to); public function setSubject($subject); public function setBody($body); public function send(); } class MyMailer implements Mailer{ private $mailer; function __construct(){ $this->mail=new Zend_Mail; //The class isn't injected this time } function setTo($to){ $this->mailer->setTo($to); } //implement the rest of the interface functions similarly } And now my Logger class can be happy :D class Logger{ private $mailer; function __construct(Mailer $mail){ $this->mail=$mail; } //rest of the code unchanged } Questions: Although I solved the mocking problem by introducing an interface, I have created a totally new class Mailer that now needs to be unit tested although it only wraps Zend_Mail which is already unit tested by the Zend team. Is there a better approach to all this? Zend_Mail's send() function could actually have a Zend_Transport object when called (i.e. public function send($transport = null)). Does this make the idea of a wrapper class more appealing? The code is in PHP, but answers doesn't have to be. This is more of a design issue than a language specific feature

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  • A few questions about how JavaScript works

    - by KayoticSully
    I originally posted on Stack Overflow and was told I might get some better answers here. I have been looking deeply into JavaScript lately to fully understand the language and have a few nagging questions that I can not seem to find answers to (Specifically dealing with Object Oriented programming. I know JavaScript is meant to be used in an OOP manner I just want to understand it for the sake of completeness). Assuming the following code: function TestObject() { this.fA = function() { // do stuff } this.fB = testB; function testB() { // do stuff } } TestObject.prototype = { fC : function { // do stuff } } What is the difference between functions fA and fB? Do they behave exactly the same in scope and potential ability? Is it just convention or is one way technically better or proper? If there is only ever going to be one instance of an object at any given time, would adding a function to the prototype such as fC even be worthwhile? Is there any benefit to doing so? Is the prototype only really useful when dealing with many instances of an object or inheritance? And what is technically the "proper" way to add methods to the prototype the way I have above or calling TestObject.prototype.functionName = function(){} every time? I am looking to keep my JavaScript code as clean and readable as possible but am also very interested in what the proper conventions for Objects are in the language. I come from a Java and PHP background and am trying to not make any assumptions about how JavaScript works since I know it is very different being prototype based. Also are there any definitive JavaScript style guides or documentation about how JavaScript operates at a low level? Thanks!

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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