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  • Saving tree-structures in Databases

    - by Nina Null
    Hello everyone. I use Hibernate/Spring and a MySQL Database for my data management. Currently I display a tree-structure in a JTable. A tree can have several branches, in turn a branch can have several branches (up to nine levels) again, or having leaves. Lately I have performanceproblemes, as soon as I want to create new branches on deeper levels. At this time a branch has a foreign key to its parent. The domainobject has access to its parent by calling getParent(), which returns the parent-branch. The deeper the level, the longer it takes to create a new branch. Microbenchmark results for creating a new branch are like: Level 1: 32 ms. Level 3: 80 ms. Level 9: 232 ms. Obviously the level (which means the number of parents) is responsible for this. So I wanted to ask, if there are any appendages to work around this kind of problem. I don’t understand why Hibernate needs to know about the whole object tree (all parents until the root) while creating a new branch. But as far as I know this can be the only reason for the delay while creating a new branch, because a branch doesn’t have any other relations to any other objects. I would be very thankful for any workarounds or suggestions. greets, jambusa

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  • How to preserve object identity across different VMs

    - by wheleph
    To be specific let me illustrate the question with Spring http-remoting example. Suppose we have such implementation of a simple interface: public SearchServiceImpl implements SearchService { public SearchJdo processSearch(SearchJdo search) { search.name = "a funky name"; return search; } } SearchJdo is itself a simple POJO. Now when we call the method from a client through http-remoting we'll get: public class HTTPClient { public static void main(final String[] arguments) { final ApplicationContext context = new ClassPathXmlApplicationContext( "spring-http-client-config.xml"); final SearchService searchService = (SearchService) context.getBean("searchService"); SearchJdo search = new SearchJdo(); search.name = "myName"; // this method actually returns the same object it gets as an argument SearchJdo search2 = searchService.processSearch(search); System.out.println(search == search2); // prints "false" } } The problem is that the search objects are different because of serializaton although from logical prospective they are the same. The question is whether there are some technique that allows to support or emulate object identity across VMs.

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  • Should my internal API classes be all in one package?

    - by Chris
    I'm hard at work packaging up an API for public consumption. As such I'm trying to limit the methods that are exposed to only those that I wish to be public and supportable. Underneath this of course there are a multitude of limited access methods. The trouble is that I have a lot of internal code that needs to access these restricted methods without making those methods public. This creates two issues: I can't create interfaces to communicate between classes as this would make these my internal methods public. I can't access protected or default methods unless I put the majority of my internal classes in the same package. So, I have around 70 or 80 internal classes in cleanly segregated packages BUT with overly permissive access modifiers. Would you say that a single package is the lesser of two evils or is there a better way to be able to mask my internal methods whilst keeping more granular packages? I'd be interested to find out the best practice here. I'm already aware of This

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  • Twitter Client using JavaScript and Oauth

    - by MP
    Is there any good tutorial or example to build a Twitter client using popup and oauth for login (Ex: http://twitgoo.com/) Also once the user logs in, the new tweets showed without any page refresh and also the ability to post a tweet without page refresh. If there is no good example, please suggest the API or libraries i need or any general suggestion.

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  • What could be the reason for continuous Full GC's during application startup.

    - by Kumar225
    What could be the reason for continuous Full GC's during application (webapplication deployed on tomcat) startup? JDK 1.6 Memory settings -Xms1024M -Xmx1024M -XX:PermSize=200M -XX:MaxPermSize=512M -XX:+UseParallelOldGC jmap output is below Heap Configuration: MinHeapFreeRatio = 40 MaxHeapFreeRatio = 70 MaxHeapSize = 1073741824 (1024.0MB) NewSize = 2686976 (2.5625MB) MaxNewSize = 17592186044415 MB OldSize = 5439488 (5.1875MB) NewRatio = 2 SurvivorRatio = 8 PermSize = 209715200 (200.0MB) MaxPermSize = 536870912 (512.0MB) 0.194: [GC [PSYoungGen: 10489K->720K(305856K)] 10489K->720K(1004928K), 0.0061190 secs] [Times: user=0.01 sys=0.00, real=0.00 secs] 0.200: [Full GC (System) [PSYoungGen: 720K->0K(305856K)] [ParOldGen: 0K->594K(699072K)] 720K->594K(1004928K) [PSPermGen: 6645K->6641K(204800K)], 0.0516540 secs] [Times: user=0.10 sys=0.00, real=0.06 secs] 6.184: [GC [PSYoungGen: 262208K->14797K(305856K)] 262802K->15392K(1004928K), 0.0354510 secs] [Times: user=0.18 sys=0.04, real=0.03 secs] 9.549: [GC [PSYoungGen: 277005K->43625K(305856K)] 277600K->60736K(1004928K), 0.0781960 secs] [Times: user=0.56 sys=0.07, real=0.08 secs] 11.768: [GC [PSYoungGen: 305833K->43645K(305856K)] 322944K->67436K(1004928K), 0.0584750 secs] [Times: user=0.40 sys=0.05, real=0.06 secs] 15.037: [GC [PSYoungGen: 305853K->43619K(305856K)] 329644K->72932K(1004928K), 0.0688340 secs] [Times: user=0.42 sys=0.01, real=0.07 secs] 19.372: [GC [PSYoungGen: 273171K->43621K(305856K)] 302483K->76957K(1004928K), 0.0573890 secs] [Times: user=0.41 sys=0.01, real=0.06 secs] 19.430: [Full GC (System) [PSYoungGen: 43621K->0K(305856K)] [ParOldGen: 33336K->54668K(699072K)] 76957K->54668K(1004928K) [PSPermGen: 36356K->36296K(204800K)], 0.4569500 secs] [Times: user=1.77 sys=0.02, real=0.46 secs] 19.924: [GC [PSYoungGen: 4280K->128K(305856K)] 58949K->54796K(1004928K), 0.0041070 secs] [Times: user=0.01 sys=0.00, real=0.01 secs] 19.928: [Full GC (System) [PSYoungGen: 128K->0K(305856K)] [ParOldGen: 54668K->54532K(699072K)] 54796K->54532K(1004928K) [PSPermGen: 36300K->36300K(204800K)], 0.3531480 secs] [Times: user=1.19 sys=0.10, real=0.35 secs] 20.284: [GC [PSYoungGen: 4280K->64K(305856K)] 58813K->54596K(1004928K), 0.0040580 secs] [Times: user=0.01 sys=0.00, real=0.01 secs] 20.288: [Full GC (System) [PSYoungGen: 64K->0K(305856K)] [ParOldGen: 54532K->54532K(699072K)] 54596K->54532K(1004928K) [PSPermGen: 36300K->36300K(204800K)], 0.2360580 secs] [Times: user=1.01 sys=0.01, real=0.24 secs] 20.525: [GC [PSYoungGen: 4280K->96K(305856K)] 58813K->54628K(1004928K), 0.0030960 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 20.528: [Full GC (System) [PSYoungGen: 96K->0K(305856K)] [ParOldGen: 54532K->54533K(699072K)] 54628K->54533K(1004928K) [PSPermGen: 36300K->36300K(204800K)], 0.2311320 secs] [Times: user=0.88 sys=0.00, real=0.23 secs] 20.760: [GC [PSYoungGen: 4280K->96K(305856K)] 58814K->54629K(1004928K), 0.0034940 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 20.764: [Full GC (System) [PSYoungGen: 96K->0K(305856K)] [ParOldGen: 54533K->54533K(699072K)] 54629K->54533K(1004928K) [PSPermGen: 36300K->36300K(204800K)], 0.2381600 secs] [Times: user=0.85 sys=0.01, real=0.24 secs] 21.201: [GC [PSYoungGen: 5160K->354K(305856K)] 59694K->54888K(1004928K), 0.0019950 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 21.204: [Full GC (System) [PSYoungGen: 354K->0K(305856K)] [ParOldGen: 54533K->54792K(699072K)] 54888K->54792K(1004928K) [PSPermGen: 36300K->36300K(204800K)], 0.2358570 secs] [Times: user=0.98 sys=0.01, real=0.24 secs] 21.442: [GC [PSYoungGen: 4280K->64K(305856K)] 59073K->54856K(1004928K), 0.0022190 secs] [Times: user=0.01 sys=0.00, real=0.01 secs] 21.444: [Full GC (System) [PSYoungGen: 64K->0K(305856K)] [ParOldGen: 54792K->54792K(699072K)] 54856K->54792K(1004928K) [PSPermGen: 36300K->36300K(204800K)], 0.2475970 secs] [Times: user=0.95 sys=0.00, real=0.24 secs] 21.773: [GC [PSYoungGen: 11200K->741K(305856K)] 65993K->55534K(1004928K), 0.0030230 secs] [Times: user=0.01 sys=0.00, real=0.01 secs] 21.776: [Full GC (System) [PSYoungGen: 741K->0K(305856K)] [ParOldGen: 54792K->54376K(699072K)] 55534K->54376K(1004928K) [PSPermGen: 36538K->36537K(204800K)], 0.2550630 secs] [Times: user=1.05 sys=0.00, real=0.25 secs] 22.033: [GC [PSYoungGen: 4280K->96K(305856K)] 58657K->54472K(1004928K), 0.0032130 secs] [Times: user=0.00 sys=0.00, real=0.01 secs] 22.036: [Full GC (System) [PSYoungGen: 96K->0K(305856K)] [ParOldGen: 54376K->54376K(699072K)] 54472K->54376K(1004928K) [PSPermGen: 36537K->36537K(204800K)], 0.2507170 secs] [Times: user=1.01 sys=0.01, real=0.25 secs] 22.289: [GC [PSYoungGen: 4280K->96K(305856K)] 58657K->54472K(1004928K), 0.0038060 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 22.293: [Full GC (System) [PSYoungGen: 96K->0K(305856K)] [ParOldGen: 54376K->54376K(699072K)] 54472K->54376K(1004928K) [PSPermGen: 36537K->36537K(204800K)], 0.2640250 secs] [Times: user=1.07 sys=0.02, real=0.27 secs] 22.560: [GC [PSYoungGen: 4280K->128K(305856K)] 58657K->54504K(1004928K), 0.0036890 secs] [Times: user=0.01 sys=0.00, real=0.01 secs] 22.564: [Full GC (System) [PSYoungGen: 128K->0K(305856K)] [ParOldGen: 54376K->54377K(699072K)] 54504K->54377K(1004928K) [PSPermGen: 36537K->36536K(204800K)], 0.2585560 secs] [Times: user=1.08 sys=0.01, real=0.25 secs] 22.823: [GC [PSYoungGen: 4533K->96K(305856K)] 58910K->54473K(1004928K), 0.0020840 secs] [Times: user=0.00 sys=0.00, real=0.01 secs] 22.825: [Full GC (System) [PSYoungGen: 96K->0K(305856K)] [ParOldGen: 54377K->54377K(699072K)] 54473K->54377K(1004928K) [PSPermGen: 36536K->36536K(204800K)], 0.2505380 secs] [Times: user=0.99 sys=0.01, real=0.25 secs] 23.077: [GC [PSYoungGen: 4530K->32K(305856K)] 58908K->54409K(1004928K), 0.0016220 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 23.079: [Full GC (System) [PSYoungGen: 32K->0K(305856K)] [ParOldGen: 54377K->54378K(699072K)] 54409K->54378K(1004928K) [PSPermGen: 36536K->36536K(204800K)], 0.2320970 secs] [Times: user=0.95 sys=0.00, real=0.23 secs] 24.424: [GC [PSYoungGen: 87133K->800K(305856K)] 141512K->55179K(1004928K), 0.0038230 secs] [Times: user=0.01 sys=0.01, real=0.01 secs] 24.428: [Full GC (System) [PSYoungGen: 800K->0K(305856K)] [ParOldGen: 54378K->54950K(699072K)] 55179K->54950K(1004928K) [PSPermGen: 37714K->37712K(204800K)], 0.4105190 secs] [Times: user=1.25 sys=0.17, real=0.41 secs] 24.866: [GC [PSYoungGen: 4280K->256K(305856K)] 59231K->55206K(1004928K), 0.0041370 secs] [Times: user=0.01 sys=0.00, real=0.00 secs] 24.870: [Full GC (System) [PSYoungGen: 256K->0K(305856K)] [ParOldGen: 54950K->54789K(699072K)] 55206K->54789K(1004928K) [PSPermGen: 37720K->37719K(204800K)], 0.4160520 secs] [Times: user=1.12 sys=0.19, real=0.42 secs] 29.041: [GC [PSYoungGen: 262208K->12901K(275136K)] 316997K->67691K(974208K), 0.0170890 secs] [Times: user=0.11 sys=0.00, real=0.02 secs]

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  • Ant: make "available" throw an understandable error?

    - by digitala
    When running ant, how do I make an <available /> block throw an adequate error message? This is what I have so far: <target name="requirements"> <available classname="foo.bar.baz" property="baz.present" /> </target> <target name="directories" depends="requirements" if="baz.present"> <mkdir dir="build" /> </target> <target name="compile" depends="directories"> <!-- build some stuff --> </target> What I'm currently seeing when requirements fails is a message complaining about the ./build dir not being available. How can I change this so that a message is displayed about the missing class, such as "foo.bar.baz is not available"?

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  • Inheriting the main method

    - by Eric
    I want to define a base class that defines a main method that instantiates the class, and runs a method. There are a couple of problems though. Here is the base class: public abstract class Strategy { abstract void execute(SoccerRobot robot); public static void main(String args) { Strategy s = new /*Not sure what to put here*/(); s.execute(new SoccerRobot()) } } And here is an example derived class: public class UselessStrategy { void execute(SoccerRobot robot) { System.out.println("I'm useless") } } It defines a simple execute method, which should be called in a main method upon usage as a the main application. However, in order to do so, I need to instantiate the derived class from within the base class's main method. Which doesn't seem to be possible. I'd rather not have to repeat the main method for every derived class, as it feels somewhat unnessary. Is there a right way of doing this?

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  • NullPointerException with Servlet

    - by RonaDona
    I am calling a Servlet using its URL address. This is the URL I am typing http://localhost:7001/ryan/olympics?action=selectCatalog&id=1 This is the Servlet's URL for sure; if I change the address I get page not found This is the code for the Servlet. public class Servlet extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet { private static final long serialVersionUID = 1L; public Servlet() { super(); } public void init(ServletConfig config) throws ServletException { System.out.println("*** initializing controller servlet."); super.init(config); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String action = request.getParameter("action"); if (action.equals("selectCatalog")) { String categoryId = request.getParameter("id"); ProductModelDAO dao4 = new ProductModelDAOImpl("jpac"); if (categoryId != null && !categoryId.trim().equals("")) { CategoryDAO dao1 = new CategoryDAOImpl("jpac"); try { Category category = dao1.getCategoryName(categoryId); request.setAttribute("category", category); } catch (Exception e) { e.printStackTrace(); } } try { @SuppressWarnings("unchecked") List<Product> products = dao4 .getProductsByCategory(categoryId); request.setAttribute("products", products); } catch (Exception e) { e.printStackTrace(); } url = "SelectCatalog.jsp"; RequestDispatcher requestDispatcher = getServletContext().getRequestDispatcher(url); requestDispatcher.forward(request, response); I get the NullPointerException pointing to the RequestDispatcher's line. Any help?

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  • Read media stream from servlet in a webpage?

    - by khue
    Hi, I have a servlet that construct response to a media file request by reading the file from server: File uploadFile = new File("C:\TEMP\movie.mov"); FileInputStream in = new FileInputStream(uploadFile); Then write that stream to the response stream. My question is how do I play the media file in the webpage using or tag to read the media stream from the response. Thank you very much. Regards K.

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  • Google App Engine - DELETE JPQL Query and Cascading

    - by Taylor Leese
    I noticed that the children of PersistentUser are not deleted when using the JPQL query below. However, the children are deleted if I perform an entityManager.remove(object). Is this expected? Why doesn't the JPQL query below also perform a cascaded delete? @OneToMany(mappedBy = "persistentUser", cascade = CascadeType.ALL) private Collection<PersistentLogin> persistentLogins; ... @Override @Transactional public final void removeUserTokens(final String username) { final Query query = entityManager.createQuery( "DELETE FROM PersistentUser p WHERE username = :username"); query.setParameter("username", username); query.executeUpdate(); }

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  • Deploying EAR file in Sun App Server having problem with proxy server setttings

    - by Nick Long
    When I am deploying certain vendor EAR file to Sun App Server, I encountered a connection timeout errror. I thought the reason might be proxy settings need to be defined so I actually defined the following -Dhttp.proxyHost=hostname -Dhttp.proxyPassword=password -Dhttp.proxyPort=8080 -Dhttp.proxyUser=username After setting these and restart domain then redeploy I encountered 407 error. Anyone have any idea what could be the issue here?

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  • Why i am getting NullPointerException for this btree method??

    - by user306540
    hi, i am writing code for btree algorithms. i am getting NullPointerException . why???? please somebody help me...! public void insertNonFull(BPlusNode root,BPlusNode parent,String key) { int i=0; BPlusNode child=new BPlusNode(); BPlusNode node=parent; while(true) { i=node.numKeys-1; if(node.leaf) { while(i>=0 && key.compareTo(node.keys[i])<0) { node.keys[i+1]=node.keys[i]; i--; } node.keys[i+1]=key; node.numKeys=node.numKeys+1; } else { while(i>=0 && key.compareTo(node.keys[i])<0) { i--; } } i++; child=node.pointers[i]; if(child!=null && child.numKeys==7) { splitChild(root,node,i,child); if(key.compareTo(node.keys[i])>0) { i++; } } node=node.pointers[i]; } }

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  • Understanding The Convolution Matrix

    - by Ryan Naddy
    I am learning about the Convolution Matrix, and I understand how they work, but I don't understand how to know before hand what the output of a Matrix will look like. For example lets say I want to add a blur to an image, I could guess 10,000+ different combinations of numbers before I get the correct one. I do know though that this formula will give me a blur effect, but I have no idea why. float[] sharpen = new float[] { 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f }; Can anyone either explain to me how this works or point me to some article, that explains this? I would like to know before hand what a possible output of the matrix will be without guessing. Basically I would like to know why do we put that number in the filed, and why not some other number?

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  • How do I integrate GUI elements from different classes at runtime?

    - by thefourthdoctor
    I'm trying to "future-proof" an application that I'm writing by splitting out those elements that are likely to change over time. In my application I need to be able to adapt to changes in the output format (e.g. today I output to a CSV file, in the future I may need to output directly to a SQL Server database, or to a web service, etc.). I'm handling this by defining an abstract class ("OutputProvider") that I will subclass for each individual case. The one aspect of this that has me stumped is how to provide a configuration GUI that is specific to each concrete class. I have a settings dialog with a tab for output configuration. On that tab I intend to provide a drop-down to select the provider and a JPanel beneath it to hold the contents of the provider-specific GUI. How do I get the right GUI in that panel at runtime and have it behave correctly with respect to events? Also, a bonus would be if there was a way to do this such that in order to add support for new providers I could simply provide a new jar or class file to be dropped in a specific folder and the application could pick that up at startup. I'm using NetBeans and Swing.

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  • What is the fastest way to learn JPA ?

    - by Jacques René Mesrine
    I'm looking for the best resources (books, frameworks, tutorials) that will help me get up to speed with JPA. I've been happily using iBatis/JDBC for my persistence needs, so I need resources that will hopefully provide comparable functions on how to do things. e.g. how to I set the isolation level for each transaction ? I know there might be 10 books on the topic, so hopefully, your recommendation could narrow down to the best 2 books. Should I start with OpenJPA or are there other opensource JPA frameworks to use ? P.S. Do suggest if I should learn JPA2 or JPA1 ? My goal ultimately is to be able to write a Google App Engine app (which uses JPA1). Thanks Jacque

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  • Licensing Android Apache Commons Math

    - by stefple
    I am about to release my first commercial software ever. I didnt study something related to programming so i am facing a problem here, which is licensing. I am not native english speaking, so i have a little bit of a problem when i read the Apache Commons License. In my software i use the Apache Commons Math library. If i understand their FAQ i just may distribute my software if i add this (the text will come up at my "info" screen inside the app): [...] \nCopyright 2012 xxxstefplexxxx \n\n This software uses Apache Commons Math Library \nThe license can be found here: \nhttp://www.apache.org/licenses/LICENSE-2.0 \n

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  • How to add an element to an array without a modification of the old array or creation a new one?

    - by Roman
    I have the following construction: for (String playerName: players). I would like to make a loop over all players plus one more special player. But I do not want to modify the players array by adding a new element to it. So, what can I do? Can I replace players in the for (String playerName: players) by something containing all elements of the players plus one more element?

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