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  • Multiple operations depending on the type of the object passed

    - by mixm
    Assuming I create a method which is passed an object and that method would perform an action depending on the object passed. How should I identify the object? I thought of using the class name to identify the object, but that may be impractical since I could easily change the class name of objects, and generate headaches during future development. Am I right? edit: for example, i have objects ball and bomb. if i have another object called wall, and the wall has the method to resolve collisions with the wall (e.g. the coordinates of the colliding ball and bomb) but have different logic depending on the colliding object (i.e. ball and bomb)

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  • designing multi module J2EE application

    - by user728947
    Might be my question is abstract or out of context, but i am asking here since i have little idea how this happens. I am wondering how big application/ platform break down there application in to multiple module and how they able to manage modules dependencies. For example in some E-commerce application they tend to break down it in various modules like pricing,promotions,shipping.import/export and many more. when we develop those application we hardly think about the underlying modules and how they have been designed to provides functionalists. Most of those module are not web-applications but are standalone module and not deployed in the web-app as jar files. can any one help me to understand how they break up things or is there any standard way to do this.any help/resources to get insight will really be helpful

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  • Writing secure java code with RMI

    - by jtnire
    Hi Everyone, This may seem like a very broad question, but any help is appreciated. I have a client/server solution written in java which uses the Cajo project (which uses RMI). I just want to try and make my solution as secure as possible, given the sensitive data that will be transferred between server and client. So far, my ideas are to make all my classes "final" as well as throw a "non-serializable" exception for all my classes in the server (except for the object bound in the RMI registry, and any objects that actually do need to be transferred of course). Can anyone think of any other ideas? I know that someone could write a malicious client - this isn't hard to do as you can find out the remote object's API using reflection. However is there anything I can do to protect a malicious client access classes/objects within the server that they are not supposed to access? Many Thanks

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  • How can I enforce Eclipse to use Sun Java?

    - by Dan
    Hi Before installing Eclipse I had Open JDK on default. Now I changed it to Sun Java. I did as Eclipse Helios was running really slow, unfortunately it is still... Do you have any ideas how to enforce it to use Java Sun? I could reinstal it however I have already Android SDK installed so I would have to do all the process again, after all thats not the correct way of solving problem I think. I'm using Ubuntu 10.10. java -version java version "1.6.0_22" Java(TM) SE Runtime Environment (build1.6.0_22-b04) Java HotSpot(TM) 64-Bit Server VM (build 17.1-b03, mixed mode) Would be grateful for any help. Best, Daniel

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  • How to use sound and images in a Java applet?

    - by Click Upvote
    Question 1: How should I structure my project so the sound and images files can be loaded most easily? Right now, I have the folder: C:\java\pacman with the sub-directory C:\java\pacman\src containing all the code, and C:\java\pacman\assets containing the images and .wav files. Is this the best structure or should I put the assets somewhere else? Question 2: What's the best way to refer to the images/sounds without using the full path e.g C:\java\pacman\assets\something.png to them? If I use the getCodeBase() function it seems to refer to the C:\java\pacman\bin instead of C:\java\pacman\. I want to use such a function/class which would work automatically when i compile the applet in a jar as well as right now when I test the applet through eclipse. Question 3: How should I load the images/sounds? This is what I'm using now: 1) For general images: import java.awt.Image; public Image getImg(String file) { //imgDir in this case is a hardcoded string containing //"C:\\java\\pacman\\assets\\" file=imgDir + file; return new ImageIcon(file).getImage(); } The images returned from this function are used in the drawImage method of the Graphics class in the paint method of the applet. 2) For a buffered image, which is used to get subImages and load sprites from a sprite sheet: public BufferedImage getSheet() throws IOException { return ImageIO.read(new File(img.getPath("pacman-sprites.png"))); } Later: public void loadSprites() { BufferedImage sheet; try { sheet=getSheet(); redGhost.setNormalImg(sheet.getSubimage(0, 60, 20, 20)); redGhost.setUpImg(sheet.getSubimage(0, 60, 20, 20)); redGhost.setDownImg(sheet.getSubimage(30, 60, 20, 20)); redGhost.setLeftImg(sheet.getSubimage(30, 60, 20, 20)); redGhost.setRightImg(sheet.getSubimage(60, 60, 20, 20)); } catch (IOException e) { System.out.println("Couldnt open file!"); System.out.println(e.getLocalizedMessage()); } } 3) For sound files: import sun.audio.*; import java.io.*; public synchronized void play() { try { InputStream in = new FileInputStream(filename); AudioStream as = new AudioStream(in); AudioPlayer.player.start(as); } catch (IOException e) { e.printStackTrace(); } }

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  • Twitter4J - Looking up profile details without logging in

    - by wvd
    Hello all, I've been using Twitter4J for a quite a while now, but I can't seem to find this particular feature. I want to be able to search on a name, and when the certain user is on twitter, I want to retrieve basic information such as tweets, followers (like you can access via http) - but how to do is in Twitter4J? Neither the code examples or the source could help me. Thanks, William van Doorn

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  • How can a servlet always perform the same task?

    - by membersound
    I want a Servlet to perform always the same tasks. Regardless of if it is a GET or POST. At the moment I just call the doGet() from doPost(), which works fine. Then I tried overriding the service() method, and I thought it would just work the same way. But it does not! The code somehow gets executed, but the response does not generate the webpage: response.getWriter(); response.println(string); This code works for the doGet/doPost methods, but not for the service. Why? Servlet: class MyWebServlet extends HttpServlet { @Override public void service(ServletRequest request, ServletResponse response) { response.setContentType("text/html"); PrintWriter out = response.getWriter(); String string = "teststring"; out.println(string); } }

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  • Show facebook status stream of a dedicated person on a website

    - by Pascal
    Hi all, I've been stomping at this all day :( I want to display a status feed of both twitter and facebook on my website. For twitter, this is not a problem, as my account is public, I can easily get the feed. Facebook however, is a whole different story! I can't seem to find an easy way to just get my last status updates and display it on my website. The code I currently have, needs authentication of the visitor, and I don't want that! This is my current code: $facebook = new Facebook($api_key, $secret); $stream = $facebook->api_client->fql_query("SELECT message,source,time FROM status WHERE uid = $user_id LIMIT 6"); I've seen several possible solutions, including the RSS feed, but as Facebook keeps changing the way their site works, none of the previous methods I've seen (including those from as late as januari) currently work! Is there anybody who can provide me with a currently working solution to this (simple?) problem?

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  • JBoss 4.2.3 - how to find path to jar file

    - by Gribbler
    I'm getting an error in a JBOSS application: Static Method [addHeader] not found on JavaBean [class com.ppnet.webservice.WebserviceHeaderWriter] I have checked the WebserviceHeaderWriter.jar that gets deployed into JBOSS and checked it in eclipse. It looks as if it should have this method on it. I think that the JBoss application might be loading a different version of the WebserviceHeaderWriter.jar without this method on it, is there a way to check the location of the file that is getting loaded?

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  • Stopping the animation after you let go of a key

    - by Michael Zeuner
    What I have right now is an animation that starts when I press space: if(input.isKeyDown(Input.KEY_SPACE)) player = movingRightSwingingSword; However when I stop clicking space my animation continues. until I move my player, how do I make it so it stops the animation right when you let go of space? A few lines Animation player, movingUp, movingDown, movingLeft, movingRight, movingRightSwingingSword; int[] duration = {200,200}; public void init(GameContainer gc, StateBasedGame sbg) throws SlickException { Image[] attackRight = {new Image("res/buckysRightSword1.png"), new Image("res/buckysRightSword2.png")}; movingRightSwingingSword = new Animation(attackRight, duration, true); } public void update(GameContainer gc, StateBasedGame sbg, int delta) throws SlickException { if(input.isKeyDown(Input.KEY_SPACE)) player = movingRightSwingingSword; } Full Code package javagame; import org.newdawn.slick.*; import org.newdawn.slick.state.*; public class Play extends BasicGameState { Animation player, movingUp, movingDown, movingLeft, movingRight, movingRightSwingingSword; Image worldMap; boolean quit = false; int[] duration = {200,200}; float playerPositionX = 0; float playerPositionY = 0; float shiftX = playerPositionX + 320; float shiftY = playerPositionY + 160; public Play(int state) { } public void init(GameContainer gc, StateBasedGame sbg) throws SlickException { worldMap = new Image("res/world.png"); Image[] walkUp = {new Image("res/buckysBack.png"), new Image("res/buckysBack.png")}; Image[] walkDown = {new Image("res/buckysFront.png"), new Image("res/buckysFront.png")}; Image[] walkLeft = {new Image("res/buckysLeft.png"), new Image("res/buckysLeft.png")}; Image[] walkRight = {new Image("res/buckysRight.png"), new Image("res/buckysRight.png")}; Image[] attackRight = {new Image("res/buckysRightSword1.png"), new Image("res/buckysRightSword2.png")}; movingUp = new Animation(walkUp, duration, false); movingDown = new Animation(walkDown, duration, false); movingLeft = new Animation(walkLeft, duration, false); movingRight = new Animation(walkRight, duration, false); //doesnt work! vvv movingRightSwingingSword = new Animation(attackRight, duration, true); player = movingDown; } public void render(GameContainer gc, StateBasedGame sbg, Graphics g) throws SlickException { worldMap.draw(playerPositionX, playerPositionY); player.draw(shiftX, shiftY); g.drawString("Player X: " + playerPositionX + "\nPlayer Y: " + playerPositionY, 400, 20); if (quit == true) { g.drawString("Resume (R)", 250, 100); g.drawString("MainMenu (M)", 250, 150); g.drawString("Quit Game (Q)", 250, 200); if (quit==false) { g.clear(); } } } public void update(GameContainer gc, StateBasedGame sbg, int delta) throws SlickException { Input input = gc.getInput(); if(input.isKeyDown(Input.KEY_UP)) { player = movingUp; playerPositionY += delta * .1f; if(playerPositionY>162) playerPositionY -= delta * .1f; } if(input.isKeyDown(Input.KEY_DOWN)) { player = movingDown; playerPositionY -= delta * .1f; if(playerPositionY<-600) playerPositionY += delta * .1f; } if(input.isKeyDown(Input.KEY_RIGHT)) { player = movingRight; playerPositionX -= delta * .1f; if(playerPositionX<-840) playerPositionX += delta * .1f; } if(input.isKeyDown(Input.KEY_LEFT)) { player = movingLeft; playerPositionX += delta * .1f; if(playerPositionX>318) playerPositionX -= delta * .1f; } if(input.isKeyDown(Input.KEY_SPACE)) player = movingRightSwingingSword; if(input.isKeyDown(Input.KEY_ESCAPE)) quit = true; if(input.isKeyDown(Input.KEY_R)) if (quit == true) quit = false; if(input.isKeyDown(Input.KEY_M)) if (quit == true) {sbg.enterState(0); quit = false;} if(input.isKeyDown(Input.KEY_Q)) if (quit == true) System.exit(0); } public int getID() { return 1; } }

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  • how to force ejb3 to reload value from data base and not use those of the context

    - by Kohan95
    Hello here I have a big problem that I hope to find help here I have two entities @Entity @Inheritance(strategy=InheritanceType.JOINED) @DiscriminatorColumn(name="Role", discriminatorType=DiscriminatorType.STRING) public class Utilisateur implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name="id") private Long id; @Column(name="nom",nullable=false) private String nom; @Column(name="Role",nullable=false, insertable=false) private String Role ; //... } @Entity @Table(name="ResCom") @DiscriminatorValue("ResCom") public class ResCom extends Utilisateur { /... } the first thing I do ResCom rsCom= new ResCom(nom,prenom, email,civilite, SysQl.crypePasse(pass)); gr.create(rsCom); I check my database I see that property is ResCom insert but when I check the value of role I get null Utilisateur tets= gr.findByEmail(email); message=tets.getEmail()+" and Role :"+tets.getRole()+""; but in my bass it ResCom !!!!! the problem disappears when I deploy the project again I hope you have a solution And thank you in advance sorry for my English

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  • Twitter rss feed 401 - unauthorisation

    - by RenegadeAndy
    Hey. I have a public twitter account and this is the rss feed for it: http://twitter.com/statuses/friends_timeline/150784631.rss The problem is, im getting an http 401 whenever im trying to access it. Can anybody explain how to stop this - and get it to work either with authentication or without! Cheers

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  • Projections.count() and Projections.countDistinct() both result in the same query

    - by Kim L
    EDIT: I've edited this post completely, so that the new description of my problem includes all the details and not only what I previously considered relevant. Maybe this new description will help to solve the problem I'm facing. I have two entity classes, Customer and CustomerGroup. The relation between customer and customer groups is ManyToMany. The customer groups are annotated in the following way in the Customer class. @Entity public class Customer { ... @ManyToMany(mappedBy = "customers", fetch = FetchType.LAZY) public Set<CustomerGroup> getCustomerGroups() { ... } ... public String getUuid() { return uuid; } ... } The customer reference in the customer groups class is annotated in the following way @Entity public class CustomerGroup { ... @ManyToMany public Set<Customer> getCustomers() { ... } ... public String getUuid() { return uuid; } ... } Note that both the CustomerGroup and Customer classes also have an UUID field. The UUID is a unique string (uniqueness is not forced in the datamodel, as you can see, it is handled as any other normal string). What I'm trying to do, is to fetch all customers which do not belong to any customer group OR the customer group is a "valid group". The validity of a customer group is defined with a list of valid UUIDs. I've created the following criteria query Criteria criteria = getSession().createCriteria(Customer.class); criteria.setProjection(Projections.countDistinct("uuid")); criteria = criteria.createCriteria("customerGroups", "groups", Criteria.LEFT_JOIN); List<String> uuids = getValidUUIDs(); Criterion criterion = Restrictions.isNull("groups.uuid"); if (uuids != null && uuids.size() > 0) { criterion = Restrictions.or(criterion, Restrictions.in( "groups.uuid", uuids)); } criteria.add(criterion); When executing the query, it will result in the following SQL query select count(*) as y0_ from Customer this_ left outer join CustomerGroup_Customer customergr3_ on this_.id=customergr3_.customers_id left outer join CustomerGroup groups1_ on customergr3_.customerGroups_id=groups1_.id where groups1_.uuid is null or groups1_.uuid in ( ?, ? ) The query is exactly what I wanted, but with one exception. Since a Customer can belong to multiple CustomerGroups, left joining the CustomerGroup will result in duplicated Customer objects. Hence the count(*) will give a false value, as it only counts how many results there are. I need to get the amount of unique customers and this I expected to achieve by using the Projections.countDistinct("uuid"); -projection. For some reason, as you can see, the projection will still result in a count(*) query instead of the expected count(distinct uuid). Replacing the projection countDistinct with just count("uuid") will result in the exactly same query. Am I doing something wrong or is this a bug? === "Problem" solved. Reason: PEBKAC (Problem Exists Between Keyboard And Chair). I had a branch in my code and didn't realize that the branch was executed. That branch used rowCount() instead of countDistinct().

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  • How to convert map to url query string?

    - by Ula Krukar
    Do you know of any utility class/library, that can convert Map into URL-friendly query string? Example: I have a map: - "param1"=12, - "param2"="cat" I want to get: param1=12&param2=cat. PS. I know I can easily write it myself, I am just surprised that I cannot find it anywhere (I checked Apache Commons so far).

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  • Problem updating collection using JPA

    - by FarmBoy
    I have an entity class Foo foo that contains Collection<Bar> bars. I've tried a variety of ways, but I'm unable to successfully update my collection. One attempt: foo = em.find(key); foo.getBars().clear(); foo.setBars(bars); em.flush; \\ commit, etc. This appends the new collection to the old one. Another attempt: foo = em.find(key); bars = foo.getBars(); for (Bar bar : bars) { em.remove(bar); } em.flush; At this point, I thought I could add the new collection, but I find that the entity foo has been wiped out. Here are some annotations. In Foo: @OneToMany(cascade = { CascadeType.ALL }, mappedBy = "foo") private List<Bar> bars; In Bar: @ManyToOne(optional = false, cascade = { CascadeType.ALL }) @JoinColumn(name = "FOO_ID") private Foo foo; Has anyone else had trouble with this? Any ideas?

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  • How to force my method to accept objects from external software?

    - by Roman
    I have a method which needs to take a callback object as an argument and then (at the moment when it's needed) my method will call a specific method of the callback object. I wrote a class called Manager which has a method called addListener. As the argument for this method I need to use a callback object which is defined by the external software. So, I define the addListener in the following way: public void addListener(Listener listener). Of course Eclipse complains because it does not know what Listener is (because the Listener is defined by the external software). The only think that I know (should know) about the Listener is that it has a method called doSomething. So, to pleasure Eclipse I add an interface before my Manager class: interface Listener { void doSomething(); } public class CTManager { ... The problem seems to be solved but then I try to test my software. So, I create a class called test. In this class I create an instance of the Manager class and try to use addListener method of this instance. I also create a class Listener, instantiate it and give the instance to the addListener. And it's the place where the problem appears. Eclipse writes that addListener is not applicable to the given argument. I think it's because it expect something from my Listenr interface but gets something from the Listener class. How can I solve this problem?

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  • J2EE and alternatives

    - by Ilya K
    Hello, I am J2SE developer but I have rich web-background (php, perl/cgi and so on) and now I am starting new project. It will have web interface, spaghetti business logic, relational database as storage and connections to other services. I do it from the scratch. My colleagues told me to use spring, spring security and struts. I look briefly at J2EE spec and found that it covers almost all aspects of enterprise application. I asked my colleagues why do they need spring and struts, but looks like they use technologies simply because they are familiar with them and not familiar with classic J2EE stack. So, my question is: what is bad about J2EE? Why do I need spring if there are JNDI lookups? It will take a day or two to create fake InitialContext for unit-tests. And that is all: I stand with out of external tools like spring. Why do I need spring-security if there is a security built in Servlets spec? I can map any request to any servlet using web.xml, no struts.xml is needed. I can use servlet-filters instead of struts interceptors. There is RMI, so I do not need spring-remote. And so on.. Why should I bother my self with all that fancy stuff if there is J2EE? I really want to find situation when J2EE is not enough. Do you have any? Thanks!

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  • Check if a class is subclass of another class in Java

    - by craesh
    Hi! I'm playing around with Java's reflection API and trying to handle some fields. Now I'm stuck with identifying the type of my fields. Strings are easy, just do myField.getType().equals(String.class). The same applies for other non-derived classes. But how do I check derived classes? E.g. LinkedList as subclass of List. I can't find any isSubclassOf(...) or extends(...) method. Do I need to walk through all getSuperClass() and find my supeclass by my own? Thanks! craesh

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  • How can CopyOnWriteArrayList be thread-safe?

    - by Shooshpanchick
    I've taken a look into OpenJDK's sources of CopyOnWriteArrayList and it seems that all write operations are protected by the same lock and read operations are not protected at all. As I understand, under JMM all accesses to a variable (both read and write) should be protected by lock or reordering effects may occur. For example, set(int, E) method contains these lines (under lock): /* 1 */ int len = elements.length; /* 2 */ Object[] newElements = Arrays.copyOf(elements, len); /* 3 */ newElements[index] = element; /* 4 */ setArray(newElements); The get(int) method, on the other hand, only does return get(getArray(), index);. In my understanding of JMM, this means that get may observe the array in an inconsistent state if statements 1-4 are reordered like 1-2(new)-4-2(copyOf)-3. Do I understand JMM incorrectly or is there any other explanations on why CopyOnWriteArrayList is thread-safe?

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  • Correct handling of return data

    - by Serhiy
    Hello, I have a question related to correct handling of returns of the DAO library I'm writing for one project. This library probably is going to be used by another people and I want to do it correctly. So I would like to know, how I should deal with return statements of the functions of my DAO. Example 1 I have function to getCustomer which should return String. In case query doesn't return any result should I return null, empty string or throw some kind of Exception? Example 2 I have function getCutomerList which return ArrayList. In case query doesn't return any result should I return null, empty ArrayList or throw some Exception? Example 3 Some sql exception was detected, what should I do: throw exception or do try..catch of the block where it can occur? What is the "good" practice or "best" practice to apply in my case? Thanks on advance, Serhiy.

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  • ArrayBlockingQueue exceeds given capacity

    - by Wojciech Reszelewski
    I've written program solving bounded producer & consumer problem. While constructing ArrayBlockingQueue I defined capacity 100. I'm using methods take and put inside threads. And I've noticed that sometimes I see put 102 times with any take's between them. Why does it happen? Producer run method: public void run() { Object e = new Object(); while(true) { try { queue.put(e); } catch (InterruptedException w) { System.out.println("Oj, nie wyszlo, nie bij"); } System.out.println("Element added"); } } Consumer run method: public void run() { while(true) { try { queue.take(); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("Element removed"); } } Part of uniq -c on file with output: 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 2 Element removed 2 Element added 102 Element removed 102 Element added

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