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  • Using thread inter-communication to increase my server app's IO throughput; not sure how

    - by Howard Guo
    My server application creates a new thread for each incoming connection. Incoming requests are serialized in a BlockingQueue. There is one worker thread taking items from the queue, produce a response and send the response through socket. I have noticed a throughput issue: Currently, worker thread is responsible of sending the response message through socket, thus severely wasting processing power and throughput. I am considering: rather than sending the response itself, why not telling network IO threads to send the response? However, when I think about thread inter-communication, I cannot yet figure out how to approach it: Worker thread will produce a response, but how will it inform the response message to IO thread? Is there a standard/best practice? Thank you.

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  • Efficient representation of Hierarchies in Hibernate.

    - by Alison G
    I'm having some trouble representing an object hierarchy in Hibernate. I've searched around, and haven't managed to find any examples doing this or similar - you have my apologies if this is a common question. I have two types which I'd like to persist using Hibernate: Groups and Items. * Groups are identified uniquely by a combination of their name and their parent. * The groups are arranged in a number of trees, such that every Group has zero or one parent Group. * Each Item can be a member of zero or more Groups. Ideally, I'd like a bi-directional relationship allowing me to get: * all Groups that an Item is a member of * all Items that are a member of a particular Group or its descendants. I also need to be able to traverse the Group tree from the top in order to display it on the UI. The basic object structure would ideally look like this: class Group { ... /** @return all items in this group and its descendants */ Set<Item> getAllItems() { ... } /** @return all direct children of this group */ Set<Group> getChildren() { ... } ... } class Item { ... /** @return all groups that this Item is a direct member of */ Set<Group> getGroups() { ... } ... } Originally, I had just made a simple bi-directional many-to-many relationship between Items and Groups, such that fetching all items in a group hierarchy required recursion down the tree, and fetching groups for an Item was a simple getter, i.e.: class Group { ... private Set<Item> items; private Set<Group> children; ... /** @return all items in this group and its descendants */ Set<Item> getAllItems() { Set<Item> allItems = new HashSet<Item>(); allItems.addAll(this.items); for(Group child : this.getChildren()) { allItems.addAll(child.getAllItems()); } return allItems; } /** @return all direct children of this group */ Set<Group> getChildren() { return this.children; } ... } class Item { ... private Set<Group> groups; /** @return all groups that this Item is a direct member of */ Set<Group> getGroups() { return this.groups; } ... } However, this resulted in multiple database requests to fetch the Items in a Group with many descendants, or for retrieving the entire Group tree to display in the UI. This seems very inefficient, especially with deeper, larger group trees. Is there a better or standard way of representing this relationship in Hibernate? Am I doing anything obviously wrong or stupid? My only other thought so far was this: Replace the group's id, parent and name fields with a unique "path" String which specifies the whole ancestry of a group, e.g.: /rootGroup /rootGroup/aChild /rootGroup/aChild/aGrandChild The join table between Groups and Items would then contain group_path and item_id. This immediately solves the two issues I was suffering previously: 1. The entire group hierarchy can be fetched from the database in a single query and reconstructed in-memory. 2. To retrieve all Items in a group or its descendants, we can select from group_item where group_path='N' or group_path like 'N/%' However, this seems to defeat the point of using Hibernate. All thoughts welcome!

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  • Xslt external parameter

    - by enrico
    In my server side TransformerFactory tfactory = TransformerFactory.newInstance(); Transformer transformer = tfactory.newTransformer( new StreamSource("mytext.xsl")); transformer.setParameter("parametro","hope"); transformer.transform( new DOMSource(document), outputStream ); --mytext.xslt-- . . . . . . why the value of $parametro isn't "hope" in my html output? Thanks

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  • How to set the email protocol in JavaMail

    - by Dusk
    If I need to get inbox messages by passing request from servlets to javamail API , how can I know the protocol in which to retrieve inbox messages? Do I have to state the protocol in request URL? I've already checked in gmail, where they haven't stated any protocol, then How can I get inbox messages based on particular protocol like: POP3 or IMAP

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  • How to define generic super type for static factory method?

    - by Esko
    If this has already been asked, please link and close this one. I'm currently prototyping a design for a simplified API of a certain another API that's a lot more complex (and potentially dangerous) to use. Considering the related somewhat complex object creation I decided to use static factory methods to simplify the API and I currently have the following which works as expected: public class Glue<T> { private List<Type<T>> types; private Glue() { types = new ArrayList<Type<T>>(); } private static class Type<T> { private T value; /* some other properties, omitted for simplicity */ public Type(T value) { this.value = value; } } public static <T> Glue<T> glueFactory(String name, T first, T second) { Glue<T> g = new Glue<T>(); Type<T> firstType = new Glue.Type<T>(first); Type<T> secondType = new Glue.Type<T>(second); g.types.add(firstType); g.types.add(secondType); /* omitted complex stuff */ return g; } } As said, this works as intended. When the API user (=another developer) types Glue<Horse> strongGlue = Glue.glueFactory("2HP", new Horse(), new Horse()); he gets exactly what he wanted. What I'm missing is that how do I enforce that Horse - or whatever is put into the factory method - always implements both Serializable and Comparable? Simply adding them to factory method's signature using <T extends Comparable<T> & Serializable> doesn't necessarily enforce this rule in all cases, only when this simplified API is used. That's why I'd like to add them to the class' definition and then modify the factory method accordingly. PS: No horses (and definitely no ponies!) were harmed in writing of this question.

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  • Using Hibernate with Dynamic Eclipse Plug-ins

    - by AlbertoPL
    I have classes that are named exactly the same across different plug-ins that I use for my application, and I'd like to be able to configure them properly with Hibernate. The problem is that it looks like Hibernate dynamically generates a class' package name when trying to find a class when it's doing its mapping. With one plug-in this scheme works, but across multiple plug-ins it's not working. It looks like Hibernate gets confused when dealing with Hibernate configuration files across multiple plug-ins. Is this because each plug-in has its own class-loader? What is the best way to proceed to make this work with the existing plug-ins and Hibernate?

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  • How to log all sql going through JBoss datasource with log4j

    - by Ichorus
    I've looked at log4jdbc (which does not support datasources), p6spy which seems to be what I am looking for but it has not been updated since 2003 which makes me nervous and lists only JBoss 3.x (we use JBoss 5), and JAMon which seems heavyweight for what I am trying to accomplish (a simple log of all SQL statements running through a JBoss application server). I was hoping that JBoss itself would have a switch to log all the sql (as Websphere does) but I cannot find any documentation for it so that functionality might not exist.

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  • Netbeans 7.2 won't open on OS X

    - by Mark van Wyk
    I installed Netbeans on OSX Mountain Lion running JDK 7. Everything was working fine. Then my machine for no reason crashed. After this I could no longer open Netbeans anymore. If I try to start Netbeans from the commandline: /Applications/NetBeans/NetBeans 7.2.app/Contents/MacOS/netbeans Then it works fine. From there I can select Netbeans About and confirm that my userdir and cachedir is: User directory: /Users/<user>/Library/Application Support/NetBeans/7.2 Cache directory: /Users/<user>/Library/Caches/NetBeans/7.2 So, I deleted these directories and tried again, but alas, I can only start netbeans via the commandline. Ideas appreciated...

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  • I have a problem with a4j:commandButton and a reredering ...

    - by ollie314
    The code below show whiche thing that is failing in my appliaction. It is a quick add information form, fill out the form and submit it add a new entry into a database and synchronize my a databasle.. This is all done with ajax. The first form submission happens correctly but the second one fails to run the desired ActionListener. The second form is posting to the server though but the saveAction isn't invoke. As you will see, I'm a real beginner with this technologies ... If someone see the problem, it will be very helpfull !! <rich:simpleTogglePanel id="quickaddActivitySimpleToogle" switchType="client" opened="false" label="#{lang.activityModule_quickAdd_panelTitle}"> <p><a4j:form id="quickAddForm"> <h:outputLabel for="activityNameInput" value="#{lang.activity_name_dp}" /> <h:inputText id="activityNameInput" value="#{activityController.quickActivityAdd.name}"> </h:inputText> <rich:spacer width="20px" /> <h:inputHidden id="activityInternalNameInput" value="#{activityController.quickActivityAdd.internalName}" /> <rich:spacer width="20px" /> <a4j:commandButton id="activityQuickAddFormSubmitBtn" reRender="activityListTable,quickAddForm" actionListener="#{activityController.saveActivity}" value="#{lang.saveBtn_header}" /> </a4j:form></p></rich:simpleTogglePanel> Thanks in advanced. ollie314

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  • What is the best way to use Guice and JMock together?

    - by Yishai
    I have started using Guice to do some dependency injection on a project, primarily because I need to inject mocks (using JMock currently) a layer away from the unit test, which makes manual injection very awkward. My question is what is the best approach for introducing a mock? What I currently have is to make a new module in the unit test that satisfies the dependencies and bind them with a provider that looks like this: public class JMockProvider<T> implements Provider<T> { private T mock; public JMockProvider(T mock) { this.mock = mock; } public T get() { return mock; } } Passing the mock in the constructor, so a JMock setup might look like this: final CommunicationQueue queue = context.mock(CommunicationQueue.class); final TransactionRollBack trans = context.mock(TransactionRollBack.class); Injector injector = Guice.createInjector(new AbstractModule() { @Override protected void configure() { bind(CommunicationQueue.class).toProvider(new JMockProvider<QuickBooksCommunicationQueue>(queue)); bind(TransactionRollBack.class).toProvider(new JMockProvider<TransactionRollBack>(trans)); } }); context.checking(new Expectations() {{ oneOf(queue).retrieve(with(any(int.class))); will(returnValue(null)); never(trans); }}); injector.getInstance(RunResponse.class).processResponseImpl(-1); Is there a better way? I know that AtUnit attempts to address this problem, although I'm missing how it auto-magically injects a mock that was created locally like the above, but I'm looking for either a compelling reason why AtUnit is the right answer here (other than its ability to change DI and mocking frameworks around without changing tests) or if there is a better solution to doing it by hand.

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  • Servlet Session - switch from URL Rewriting to Cookie

    - by lajuette
    Situation: I have a "dumb" Javascript frontend that can contact some kind of SSO middleware (MW). The MW can obtain sessions by issuing requests that contain authentication credentials (username, password). I.e. the session will be created for a certain user. My frontend needs to "restart" the session to gain the user's permissions to the target system. For that i need a valid session cookie. The target system is not under my control (could be a more or less public WFS, WMS, etc.), so i cannot add any SSO mechanism to it. Question: Is it possible to "steal" a Session forging a request which URL contains a valid session ID in the jsessionid parameter? Goal : Issue such a request to a Servlet and make it respond with a Set-Cookie header that contains the same id. That way the frontend joins the session and may do whatever the user, which was used to create the session, is able to do.

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  • How to fix IllegalStateException error when trying to update a listview?

    - by Michael Vetrano
    Hi guys, I am trying to get this code to run, but I get an IllegalStateException when I run this code saying that the content of the listview wasn't notified, yet I have a notification upon updating the data. This is a custom listview adapter. Here is the relevant part of my code: class LoadingThread extends Thread { public void run() { int itemsOriginallyLoaded = 0; synchronized( items ) { itemsOriginallyLoaded = items.size(); } for( int i = itemsOriginallyLoaded ; i < itemsToLoad ; ++i ) { Log.d( LOG_TAG, "Loading item #"+i ); //String item = "FAIL"; //try { String item = "FAIL"; try { item = stockGrabber.getStockString(dataSource.get(i)); } catch (ApiException e) { Log.e(LOG_TAG, "Problem making API request", e); } catch (ParseException e) { Log.e(LOG_TAG, "Problem parsing API request", e); } //} catch (ApiException e) { // Log.e(TAG, "Problem making API request", e); //} catch (ParseException e) { // Log.e(TAG, "Problem parsing API request", e); //} synchronized( items ) { items.add( item ); } itemsLoaded = i+1; uiHandler.post( updateTask ); Log.d( LOG_TAG, "Published item #"+i ); } if( itemsLoaded >= ( dataSource.size() - 1 ) ) allItemsLoaded = true; synchronized( loading ) { loading = Boolean.FALSE; } } } class UIUpdateTask implements Runnable { public void run() { Log.d( LOG_TAG, "Publishing progress" ); notifyDataSetChanged(); } }

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  • Server-initiated Rendering: EJB -> FacesContext?

    - by egbokul
    I've already asked this question on the Icefaces forum, but meanwhile I realized that this is a more generic problem. I'd like to update parts of a JSF page when I get a message in my MDB. The problem is, how do I get the FacesContext from the EJB container? In the message processing function FacesContext.getCurrentInstance() returns null. I've also tried to make a JSF managed bean be a MDB, but I couldn't (it seems you can't have both in the same class?). Since I'm a beginner in the JSF world I'm kind of stuck now. Is there a way to make it work? (Glassfish v3 + Netbeans 6.8, JSF2 + Icefaces 2.0 alpha2)

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  • Arithmetic operator confusion

    - by Dusk
    Why I'm getting two different values while using the arithmetic operators for the same value of variables. I've just altered little bit my second program, which is resulted in giving me the different output. Could anyone please tell me why? int number=113; int rot=0; rot=number%10; rot*=100+number/10; System.out.println(rot);//333 int number=113; int rot=0; rot=number%10; rot=rot*100+number/10; System.out.println(rot);//311

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  • Can Box Layout accept size of included elements?

    - by Roman
    I used myPanel.setLayout(new BoxLayout(myPanel, BoxLayout.Y_AXIS)); to order panels vertically (one under another one). But myPanel defined in the shown way change the included panel. In more details, it tries to set the same hight and width for the included panels. Can it be changed? Can BoxLayout adopt size of the included elements?

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  • Android file-creation fails.

    - by Alxandr
    I use the following code to create a folder "mymir" and a file ".nomedia" (in the mymir-folder) on the sdcard of an android unit. However, somehow it fails with the exception that the folder the ".nomedia"-file is to be placed in dosn't exist. Here's the code: private String EnsureRootDir() throws IOException { File sdcard = Environment.getExternalStorageDirectory(); File mymirFolder = new File(sdcard.getAbsolutePath() + "/mymir/"); if(!mymirFolder.exists()) { File noMedia = new File(mymirFolder.getAbsolutePath() + "/.nomedia"); noMedia.mkdirs(); noMedia.createNewFile(); } return mymirFolder.getAbsolutePath(); }

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  • Using an object in an if statement... (Android)

    - by James Rattray
    I have an object variable Object test = Spinner.getSelectedItem(); -It gets the selected item from the Spinner (called spinner) and names the item 'test' I want to do an if statement related to that object e.g: 'if (test = "hello") { //do something }' But it appears not to work.... Can someone give me some help? -Do I have to use a different if? or convert the object to string etc.? Thanks alot... James

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  • Caching Authentication Data

    - by PartlyCloudy
    Hi, I'm currently implementing a REST web service using CouchDB and RESTlet. The RESTlet layer is mainly for authentication and some minor filtering of the JSON data served by CouchDB: Clients <= HTTP = [ RESTlet <= HTTP = CouchDB ] I'm using CouchDB also to store user login data, because I don't want to add an additional database server for that purpose. Thus, each request to my service causes two CouchDB requests conducted by RESTlet (auth data + "real" request). In order to keep the service as efficent as possible, I want to reduce the number of requests, in this case redundant requests for login data. My idea now is to provide a cache (i.e.LRU-Cache via LinkedHashMap) within my RESTlet application that caches login data, because HTTP caching will probabily not be enough. But how do I invalidate the cache data, once a user changes the password, for instance. Thanks to REST, the application might run on several servers in parallel, and I don't want to create a central instance just to cache login data. Currently, I save requested auth data in the cache and try to auth new requests by using them. If a authentication fails or there is now entry available, I'll dispatch a GET request to my CouchDB storage in order to obtain the actual auth data. So in a worst case, users that have changed their data will perhaps still be able to login with their old credentials. How can I deal with that? Or what is a good strategy to keep the cache(s) up-to-date in general? Thanks in advance.

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  • problem in adding image to JFrame

    - by firestruq
    Hi, I'm having problems in adding a picture into JFrame, something is missing probebly or written wrong. here are the classes: main class: public class Tester { public static void main(String args[]) { BorderLayoutFrame borderLayoutFrame = new BorderLayoutFrame(); borderLayoutFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); borderLayoutFrame.setSize(600,600); borderLayoutFrame.setVisible(true); } } public class BorderLayoutFrame extends JFrame implements ActionListener { private JButton buttons[]; // array of buttons to hide portions private final String names[] = { "North", "South", "East", "West", "Center" }; private BorderLayout layout; // borderlayout object private PicPanel picture = new PicPanel(); // set up GUI and event handling public BorderLayoutFrame() { super( "Philosofic Problem" ); layout = new BorderLayout( 5, 5 ); // 5 pixel gaps setLayout( layout ); // set frame layout buttons = new JButton[ names.length ]; // set size of array // create JButtons and register listeners for them for ( int count = 0; count < names.length; count++ ) { buttons[ count ] = new JButton( names[ count ] ); buttons[ count ].addActionListener( this ); } add( buttons[ 0 ], BorderLayout.NORTH ); // add button to north add( buttons[ 1 ], BorderLayout.SOUTH ); // add button to south add( buttons[ 2 ], BorderLayout.EAST ); // add button to east add( buttons[ 3 ], BorderLayout.WEST ); // add button to west add( picture, BorderLayout.CENTER ); // add button to center } // handle button events public void actionPerformed( ActionEvent event ) { } } I'v tried to add the image into the center of layout. here is the image class: public class PicPanel extends JPanel { Image img; private int width = 0; private int height = 0; public PicPanel() { super(); img = Toolkit.getDefaultToolkit().getImage("table.jpg"); } public void paintComponent(Graphics g) { super.paintComponents(g); if ((width <= 0) || (height <= 0)) { width = img.getWidth(this); height = img.getHeight(this); } g.drawImage(img,0,0,width,height,this); } } Please your help, what is the problem? thanks BTW: i'm using eclipse, which directory the image suppose to be in?

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