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• Can I close and reopen a socket?

  - by Roman

  I learned an example of usage of sockets. In this example a client sends a request to a server to open a socket and then the server (listening to a specific port) opens a socket and everything is fine, socket is "opened" from both sides (client and server). But it is still not clear to me how flexible is this stuff. For example, is it possible for the client to close an opened (from both ends) socket and to reopen it again (under condition that the server keeps the socket opened). Is it possible for the server to "know" that a socket was closed on the client side? Is it possible for the client to know that a socket was closed on the server side?

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• Facebook Connect for BlackBerry

  - by Gadi

  Hi I'm looking for a solution similar to the iPhone Facebook Connect (http://wiki.developers.facebook.com/index.php/Facebook%5FConnect%5Ffor%5FiPhone) for the BlackBerry platform. Basically, I need my users to authenticate against Facebook from within a native BlackBerry application (so, not a Web based mobile application). Is there a library I could use, and if not, what will be the correct approach to achieve this? Thanks in advance!

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• Should integration testing of DAOs be done in an application server?

  - by HDave

  I have a three tier application under development and am creating integration tests for DAOs in the persistence layer. When the application runs in Websphere or JBoss I expect to use the connection pooling and transaction manager of those application servers. When the application runs in Tomcat or Jetty, we'll be using C3P0 for pooling and Atomikos for transactions. Because of these different subsystems, should the DAO's be tested in a fully configured application server environment or should we handle those concerns when integration testing the service layer? Currently we plan on setting up a simple JDBC data source with non-JTA (i.e. resource-local) transactions for DAO integration testing, thus no application server is involved....but this leaves me wondering about environmental problems we won't uncover.

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• Persistence unit is not persistent

  - by etam

  I need persistence unit that creates embedded database which stays persistent after closing EntityManager. This is my PU: <persistence-unit name="hello-jpa" transaction-type="RESOURCE_LOCAL"> <class>hello.jpa.User</class> <properties> <property name="hibernate.show_sql" value="true"/> <property name="hibernate.format_sql" value="true"/> <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/> <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/> <property name="hibernate.connection.username" value="sa"/> <property name="hibernate.connection.password" value=""/> <property name="hibernate.connection.url" value="jdbc:hsqldb:target/hsql.db"/> <property name="hibernate.hbm2ddl.auto" value="update"/> </properties> </persistence-unit> And it deletes data after closing application.

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• Searching for a converter

  - by monika

  I am searching for a converter which can convert gif image text to word document. The data should be editable.

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• SWT Drag and Drop support for Text widget

  - by bryantsai

  I've written an application recently using SWT. In one of its dialog box, I have a few widgets, one of which is Text, which is designed to support DND with other widgets. I've first added DND support for the 2 Tree widgets on the same dialog box (both drag source and drop target). Before I added DND support for that Text widget, I noticed that on Linux platform (gtk), SWT Text widget automatically get drag and drop support. That is, I can already drag from the other Tree widgets and drop on this Text (at any position to inserted there), as well as selecting and dragging any text from this Text to other Tree or Text widget. However, this is only working on Linux platform but not on Windows. The same program, if running on Windows, will not have any DND support for that Text widget (Tree widgets of course have DND support since I specifically write for them). So here's what I want to achieve on Windows as well: drop text at any position in Text widget. before dropping and while hovering, able to see the caret position clearly where the intended position to drop. caret position should move along with the mouse cursor. support multi-line in Text widget SOLUTION: DropTarget target = new DropTarget(sytledText, DND.DROP_MOVE | DND.DROP_COPY); target.setTransfer(new Transfer[] { TextTransfer.getInstance() }); target.addDropListener(new StyleTextDropTargetEffect(sytledText)); Use StyledText instead of Text widget Use StyledTextDropTargetEffect (or extend it) and add it as dr op listener

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• HttpClient multithread performance

  - by pepper

  I have an application which downloads more than 4500 html pages from 62 target hosts using HttpClient (4.1.3 or 4.2-beta). It runs on Windows 7 64-bit. Processor - Core i7 2600K. Network bandwidth - 54 Mb/s. At this moment it uses such parameters: DefaultHttpClient and PoolingClientConnectionManager; Also it hasIdleConnectionMonitorThread from http://hc.apache.org/httpcomponents-client-ga/tutorial/html/connmgmt.html; Maximum total connections = 80; Default maximum connections per route = 5; For thread management it uses ForkJoinPool with the parallelism level = 5 (Do I understand correctly that it is a number of working threads?) In this case my network usage (in Windows task manager) does not rise above 2.5%. To download 4500 pages it takes 70 minutes. And in HttpClient logs I have such things: DEBUG ForkJoinPool-2-worker-1 [org.apache.http.impl.conn.PoolingClientConnectionManager]: Connection released: [id: 209][route: {}-http://stackoverflow.com][total kept alive: 6; route allocated: 1 of 5; total allocated: 10 of 80] Total allocated connections do not raise above 10-12, in spite of that I've set it up to 80 connections. If I'll try to rise parallelism level to 20 or 80, network usage remains the same but a lot connection time-outs will be generated. I've read tutorials on hc.apache.org (HttpClient Performance Optimization Guide and HttpClient Threading Guide) but they does not help. Task's code looks like this: public class ContentDownloader extends RecursiveAction { private final HttpClient httpClient; private final HttpContext context; private List<Entry> entries; public ContentDownloader(HttpClient httpClient, List<Entry> entries){ this.httpClient = httpClient; context = new BasicHttpContext(); this.entries = entries; } private void computeDirectly(Entry entry){ final HttpGet get = new HttpGet(entry.getLink()); try { HttpResponse response = httpClient.execute(get, context); int statusCode = response.getStatusLine().getStatusCode(); if ( (statusCode >= 400) && (statusCode <= 600) ) { logger.error("Couldn't get content from " + get.getURI().toString() + "\n" + response.toString()); } else { HttpEntity entity = response.getEntity(); if (entity != null) { String htmlContent = EntityUtils.toString(entity).trim(); entry.setHtml(htmlContent); EntityUtils.consumeQuietly(entity); } } } catch (Exception e) { } finally { get.releaseConnection(); } } @Override protected void compute() { if (entries.size() <= 1){ computeDirectly(entries.get(0)); return; } int split = entries.size() / 2; invokeAll(new ContentDownloader(httpClient, entries.subList(0, split)), new ContentDownloader(httpClient, entries.subList(split, entries.size()))); } } And the question is - what is the best practice to use multi threaded HttpClient, may be there is a some rules for setting up ConnectionManager and HttpClient? How can I use all of 80 connections and raise network usage? If necessary, I will provide more code.

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• Design for tagging system in GAE-J

  - by tempy

  I need a simple tagging system in GAE-J. As I see it, the entity that is being tagged should have a collection of keys referring to the tags with which it's associated. A tag entity should simply contain the tag string itself, and a collection of keys pointing to the entities associated with the tag. When an entity's list of tags is altered, the system will create a new tag if the tag is unknown, and then append the entity's key to that tag's key collection. If the tag already exists, then the entity's key is simply appended to the tag's key collection. This seems relatively straight-forward and uncontroversial to me, but I would like some feedback on this design, just to be sure.

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• Junit exception test

  - by Prithis

  I have two tests to check the expected exception throw. I am using Junit 4 and has following syntax. @Test(expected=IllegalArgumentException.class) public void testSomething(){ .......... } One of the tests fail even though IllegalArgumentException is thrown and the other passes. Any idea whats missing?? I modified the test which is failing to following and it passes. public void testSomething(){ try{ ............ //line that throws exception fail(); }catch(IllegalArgumentException e) { } }

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• Clean up upon the kill signal

  - by Begui

  How do you handle clean up when the program receives a kill signal? For instance, there is an application I connect to that wants any third party app (my app) to send a finish command. What is the best say to send that finish command when my app has been destroyed with a kill -9?

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• error in midlet while implementing command..

  - by garima

  hi I have imported import com.sun.lwuit.Command; import javax.microedition.midlet.; import javax.microedition.lcdui.; in my code but still the following errors are coming... exitCommand = new Command("Exit", Command.EXIT, 2); //line 1 textbox.addCommand(exitCommand); //line 2 Command.EXIT cannot be resolved.. The method addCommand(Command) in the type Displayable is not applicable for the arguments (Command)

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• hibernate c3p0 broken pipe

  - by raven_arkadon

  Hi, I'm using hibernate 3 with c3p0 for a program which constantly extracts data from some source and writes it to a database. Now the problem is, that the database might become unavailable for some reasons (in the simplest case: i simply shut it down). If anything is about to be written to the database there should not be any exception - the query should wait for all eternity until the database becomes available again. If I'm not mistaken this is one of the things the connection pool could do for me: if there is a problem with the db, just retry to connect - in the worst case for infinity. But instead i get a broken pipe exception, sometimes followed by connection refused and then the exception is passed to my own code, which shouldn't happen. Even if I catch the exception, how could i cleanly reinitialize hibernate again? (So far without c3p0 i simply built the session factory again, but i wouldn't be surprised if that could leak connections (or is it ok to do so?)). The database is Virtuoso open source edition. My hibernate.xml.cfg c3p0 config: <property name="hibernate.connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</property> <property name="hibernate.c3p0.breakAfterAcquireFailure">false</property> <property name="hibernate.c3p0.acquireRetryAttempts">-1</property> <property name="hibernate.c3p0.acquireRetryDelay">30000</property> <property name="hibernate.c3p0.automaticTestTable">my_test_table</property> <property name="hibernate.c3p0.initialPoolSize">3</property> <property name="hibernate.c3p0.minPoolSize">3</property> <property name="hibernate.c3p0.maxPoolSize">10</property> btw: The test table is created and i get tons of debug output- so it seems it actually reads the config.

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• Putting Select Statement on Hibernate Transaction

  - by Mark Estrada

  Hi All, I have been reading the net for a while regarding Hibernate but I can seem to understand one concept regarding Transaction. On some site that I have visit, Select statements are in transaction mode like this. public List<Book> readAll() { Session session = HibernateUtil.getSessionFactory() .getCurrentSession(); session.beginTransaction(); List<Book> booksList = session.createQuery("from Book").list(); session.getTransaction().commit(); return booksList; } While on some site, it does not advocate the use of transaction on Select statements public List<Book> readAll() { Session session = HibernateUtil.getSessionFactory() .getCurrentSession(); List<Book> booksList = session.createQuery("from Book").list(); return booksList; } I am thinking which one should I follow. Any thoughts please? Are transactions needed on Select Statements or not? Thanks

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• JMF. Create new custom streamdatasource

  - by Afro Genius

  Hi there. I am looking to create a means of building a DataSource object (and hence a Processor) that gets data from a stream instead of a file, RTP, and so on. I am writing a module for a much larger application that is meant to transparently transcode audio data. Going through the JMF docs only specify how to create a source from file however I need to be able to create a source from a stream within my application. Any idea where I can start looking?

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• How do I left join tables in unidirectional many-to-one in Hibernate?

  - by jbarz

  I'm piggy-backing off of http://stackoverflow.com/questions/2368195/how-to-join-tables-in-unidirectional-many-to-one-condition. If you have two classes: class A { @Id public Long id; } class B { @Id public Long id; @ManyToOne @JoinColumn(name = "parent_id", referencedColumnName = "id") public A parent; } B - A is a many to one relationship. I understand that I could add a Collection of Bs to A however I do not want that association. So my actual question is, Is there an HQL or Criteria way of creating the SQL query: select * from A left join B on (b.parent_id = a.id) This will retrieve all A records with a Cartesian product of each B record that references A and will include A records that have no B referencing them. If you use: from A a, B b where b.a = a then it is an inner join and you do not receive the A records that do not have a B referencing them. I have not found a good way of doing this without two queries so anything less than that would be great. Thanks.

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• How can i edit OSGi bundles manifest file in Netbeans 6.9?

  - by Deniz Acay

  I'm using Netbeans 6.9 RC2 and Maven OSGi Bundle project template. Actually i dont want to test my bundles in Netbeans environment so i copy the jar file to the OSGi container directory and install it from command line. But when i want to see its headers from OSGi console, i see a lot of Netbeans related unnecessary stuff. Is it possible to edit the contents of the manifest file in Netbeans?

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• Safe to pass objects to C functions when working in JNI Invocation API?

  - by bubbadoughball

  I am coding up something using the JNI Invocation API. A C program starts up a JVM and makes calls into it. The JNIenv pointer is global to the C file. I have numerous C functions which need to perform the same operation on a given class of jobject. So I wrote helper functions which take a jobject and process it, returning the needed data (a C data type...for example, an int status value). Is it safe to write C helper functions and pass jobjects to them as arguments? i.e. (a simple example - designed to illustrate the question): int getStatusValue(jobject jStatus) { return (*jenv)->CallIntMethod(jenv,jStatus,statusMethod); } int function1() { int status; jobject aObj = (*jenv)->NewObject (jenv, aDefinedClass, aDefinedCtor); jobject j = (*jenv)->CallObjectMethod (jenv, aObj, aDefinedObjGetMethod) status = getStatusValue(j); (*jenv)->DeleteLocalRef(jenv,aObj); (*jenv)->DeleteLocalRef(jenv,j); return status; } Thanks.

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• Correct use of Classloader (especially in Android)

  - by Sebi

  I read some documentations about classloaders, but im still not sure where and why they are needed. The Android API says: Loads classes and resources from a repository. One or more class loaders are installed at runtime. These are consulted whenever the runtime system needs a specific class that is not yet available in-memory. So if i understand this correct, there can be many classlaoders which are responsible for loading new classes. But how the system decides which to use? And in which situation should a developer instantiate a new classloader? In the Android API for Intent there is a method public void setExtrasClassLoader (ClassLoader loader) The description says: Sets the ClassLoader that will be used when unmarshalling any Parcelable values from the extras of this Intent. So can i define there a special classloader so that i can pass object with an Intent which are not defined in the receiving activity? An example: If activity A which is located in Project A (in Eclipse) defines an object which i want to send to Activity B in Project B using putExtra of the Intent object. If this object which is send over the Intent is not defined (source code in project B), then there is a NoClassDefFoundException. So can i use the method setExtraClassloader to avoid this exception? If yes, how can i decide which classloader object i have to pass? And how do I instantiate it correctly?

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• ListAdapters and WrapperListAdapter algorithm

  - by Matty F

  This logic is written in a function with signature private void showDialog(final AdapterView<? extends Adapter> parent, String title, String message, final Tag subject) Is there a better way of doing this? // refresh adapter SimpleCursorAdapter adapter; if (parent.getAdapter() instanceof WrapperListAdapter) { adapter = (SimpleCursorAdapter) ((WrapperListAdapter) parent.getAdapter()).getWrappedAdapter(); } else { adapter = (SimpleCursorAdapter) parent.getAdapter(); } adapter.getCursor().requery(); adapter.notifyDataSetChanged(); Also, is there any point in having AdapterView<? extends Adapter> in the signature and not just AdapterView<?>?

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• using internationalization on list data

  - by singh

  i am using Struts2 in application. <s:iterator value="listObject"> <s:component template="abc.vm"> <s:param name="text" value="listValue" /> <s:param name="prefix" value="listIndex" /> </s:component> </s:iterator> listValue is a values of list. i am using iterator to traverse the list. now on listValue, i want to put here internationalization concept.so that all the list value can be display based on Locale which store in a list. please suggest!

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• Embed View Only Word Document in Webpage

  - by Holograham

  Working a on a Google Web Toolkit project. I want to show a word document in a webpage. Does not have to be the MS Word 2007 view. Any way to do this?

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• Android Convert Video To MP4

  - by Isaac Waller

  I have a Android app. It recieves videos in .flv format which is unplayable by the Android phone. I was wondering how to convert the file to MP4. I could use FFMPEG, but I do not know how I would get it onto the phone, and how it would work on multiple phones if it was compiled for a single one.

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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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• Autocomplete server-side implementation

  - by toluju

  What is a fast and efficient way to implement the server-side component for an autocomplete feature in an html input box? I am writing a service to autocomplete user queries in our web interface's main search box, and the completions are displayed in an ajax-powered dropdown. The data we are running queries against is simply a large table of concepts our system knows about, which matches roughly with the set of wikipedia page titles. For this service obviously speed is of utmost importance, as responsiveness of the web page is important to the user experience. The current implementation simply loads all concepts into memory in a sorted set, and performs a simple log(n) lookup on a user keystroke. The tailset is then used to provide additional matches beyond the closest match. The problem with this solution is that it does not scale. It currently is running up against the VM heap space limit (I've set -Xmx2g, which is about the most we can push on our 32 bit machines), and this prevents us from expanding our concept table or adding more functionality. Switching to 64-bit VMs on machines with more memory isn't an immediate option. I've been hesitant to start working on a disk-based solution as I am concerned that disk seek time will kill performance. Are there possible solutions that will let me scale better, either entirely in memory or with some fast disk-backed implementations? Edits: @Gandalf: For our use case it is important the the autocompletion is comprehensive and isn't just extra help for the user. As for what we are completing, it is a list of concept-type pairs. For example, possible entries are [("Microsoft", "Software Company"), ("Jeff Atwood", "Programmer"), ("StackOverflow.com", "Website")]. We are using Lucene for the full search once a user selects an item from the autocomplete list, but I am not yet sure Lucene would work well for the autocomplete itself. @Glen: No databases are being used here. When I'm talking about a table I just mean the structured representation of my data. @Jason Day: My original implementation to this problem was to use a Trie, but the memory bloat with that was actually worse than the sorted set due to needing a large number of object references. I'll read on the ternary search trees to see if it could be of use.

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• using volatile keyword

  - by sap

  As i understand, if we declare a variable as volatile, then it will not be stored in the local cache. Whenever thread are updating the values, it is updated to the main memory. So, other threads can access the updated value. But in the following program both volatile and non-volatile variables are displaying same value. The volatile variable is not updated for the second thread. Can anybody plz explain this why testValue is not changed. class ExampleThread extends Thread { private int testValue1; private volatile int testValue; public ExampleThread(String str){ super(str); } public void run() { if (getName().equals("Thread 1 ")) { testValue = 10; testValue1= 10; System.out.println( "Thread 1 testValue1 : " + testValue1); System.out.println( "Thread 1 testValue : " + testValue); } if (getName().equals("Thread 2 ")) { System.out.println( "Thread 2 testValue1 : " + testValue1); System.out.println( "Thread 2 testValue : " + testValue); } } } public class VolatileExample { public static void main(String args[]) { new ExampleThread("Thread 1 ").start(); new ExampleThread("Thread 2 ").start(); } } output: Thread 1 testValue1 : 10 Thread 1 testValue : 10 Thread 2 testValue1 : 0 Thread 2 testValue : 0

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