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  • MySQL with Java: Open connection only if possible

    - by emempe
    I'm running a database-heavy Java application on a cluster, using Connector/J 5.1.14. Therefore, I have up to 150 concurrent tasks accessing the same MySQL database. I get the following error: Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Too many connections This happens because the server can't handle so many connections. I can't change anything on the database server. So my question is: Can I check if a connection is possible BEFORE I actually connect to the database? Something like this (pseudo code): check database for open connection slots if (slot is free) { Connection cn = DriverManager.getConnection(url, username, password); } else { wait ... } Cheers

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  • Custom ArrayList serialization

    - by rayman
    Hi, i was trying to serialize an ArrayList which contacins custom objects. I`am serializing it in a servlet(server side), and deserialize at the client side. (using ObjectOutputStream,ObjectInputStream) it worked fine, when I work with ArrayList< String but when i tried it with ArrayList< MyObject i couldnt get any results in the client side, this is the exception: java.lang.ClassNotFoundException: web.MyObject *ofcourse that i have done this: MyObject implements Serializable ... MyObject contains only String fields in it. what have I done worng? Thanks, ray.

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  • HttpsURLConnection failing intermittently to the same URL

    - by Arkaitz Jimenez
    I think I'm experiencing the same as http://groups.google.com/group/android-developers/msg/9d37d64aad0ee357 This is Android 1.5 SDK. I happen to call several times below code(which is in a method) with the same url and it fails intermittently. When it fails, there is no exception, the stream is empty so the readConnection fails, and getResponseCode returns -1. Global caching is disabled, setDefaultUseCaches(false); I suppose there must be some kind of url connection object pool somewhere. Any idea on how can I workaround this? HttpURLConnection connection = null; try { URL url = new URL(this.url); connection = (HttpURLConnection) url.openConnection(); connection.setRequestProperty("Authorization", "basic " + Base64Coder.encodeString(user + ":" + password)); connection.setRequestProperty("User-Agent", userAgent); connection.connect(); readConnection(connection.getInputStream()); connection.disconnect(); } catch (IOException ex) { reportException(ex, connection.getResponseCode()) } catch (ParserException ex) { reportException(ex, connection.getResponseCode()) }

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  • How to make IIS wait for WCF service gets ready?

    - by Kamarey
    I have a WCF service hosted in IIS 7. It takes some minutes until this service finish to load its data and ready for external calls. Data loads in internal thread. The problem is that from IIS point the service is ready just after it was activated (by some call), and it process a request without waiting for data to be loaded. Is it possible to tell IIS that the service is still loading and make this service unavailable for requests? No problem if such request will throw an exception.

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  • Two collections manyToOne to same primary key

    - by Ethiel
    Hi, guys, I'm coding a web page in Hibernate-JPA and Oracle. I need the following: I have two classes: Place and Home. I need two collections of type Place in every Home: I do the following: Home: @ManyToOne @JoinColumn(name="ID_PLACES") private List<Places>places1; @ManyToOne @JoinColumn(name="ID_PLACES") private List<Places>Places2; However, hibernate got an exception (repeated column) and forces to me to mapping with insert and update to false. How Can I get Two ManyToOne relationship to same primary key with insert a true?.

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  • Hibernate, alter identifier/primary key

    - by Schildmeijer
    I receive the following exception when Im trying to alter my @ID in an @Entity. identifier of an instance of com.google.search.pagerank.ItemEntity was altered from 1 to 2. I know that im altering the primary key in my table. Im using JPA-annotations. I solved this by using this single HQL query: update Table set name=:newName where name=:oldName instead of using the more oo approach: beginTransaction(); T e = session.load(...); e.setName(newName); session.saveOrUdate(e); commit(); Any idea what the diff is?

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  • casting a generic array in java

    - by liloboy
    The implementation is for a linked list in java : public AnyType[] toArr() { AnyType[] arr = (AnyType[]) new Object[size]; int i = 0; Node<AnyType> current = head.next; while (cur != head){ arr[i] = current.data;// fill the array i++; current = current.next; } return arr; } public static void main(String[] args) { System.out.println(ll.toArr().toString()); } The error that I get: Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.Integer; Thanks.

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  • UInt32 to IntPtr

    - by ffenix
    I have the following problem: public class ListenThread : SocketInvoke { [DllImport("Ws2_32", CharSet = CharSet.Auto)] public unsafe static extern UInt32 WSAWaitForMultipleEvents(UInt32 cEvents, IntPtr hEventObject, UInt32 fWaitAll, UInt32 dwTimeout, Boolean fAlertable); public void ListenConnections(NetSharedData data) { while (true) { unsafe { if (WSAWaitForMultipleEvents((UInt32)1, data.signal, (UInt32)0, (UInt32)100, false) != WSA_WAIT_TIMEOUT) { } } } } data.signal is a UInt32 how i can cast it to IntPtr?, i try: IntPtr signal = (IntPtr)data.signal; but it doesn't work because i need a pointer to data.signal (UInt32) type and not the int value as an pointer, that will make a memory exception. An C++ example of what i need: int signal = 0; int* psignal = &signal;

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  • Lambda expressions and nullable types

    - by Mathew
    I have two samples of code. One works and returns the correct result, one throws a null reference exception. What's the difference? I know there's some magic happening with capturing variables for the lambda expression but I don't understand what's going on behind the scenes here. int? x = null; bool isXNull = !x.HasValue; // this works var result = from p in data.Program where (isXNull) select p; return result.Tolist(); // this doesn't var result2 = from p in data.Program where (!x.HasValue) select p; return result2.ToList();

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  • Adapting methods which return true/false

    - by James P.
    What's the best practise when adapting C-style functions which return a true/false to Java? Here's a simple method to illustrate where the problem lies. public static boolean fileNameEndsWithExtension( String filename, String fileExtension) { return filename.endsWith( fileExtension ); } Note that there's probably a more elegant way of filtering files (feel free to comment on this). Anyway, if filename is a null value, does one: Return a false if filename is null? If so, how does one go about distinguishing between the case where filename is null and the case where the String or file name doesn't end with a given file extension? Change the return type to the wrapper class Boolean which allows a null value. Throw an Exception and force the programmer to make sure that a null value is never passed to the method? Use another solution?

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  • SQL Server Service Broker Service Disappearing (Automatically Deleted)?

    - by mwigdahl
    I've implemented a messaging system over SQL Server Service Broker. It is working great, with the sole exception that every once in a while (maybe once per week per server) my initiator service just vanishes without a trace. The corresponding queue is still there, but the service is missing. Obviously this causes problems in my system. It's a simple matter to recreate the service by hand, but I'm confused as to what might cause this behavior. I understand that automatic poison message handling causes queues to be disabled, but I don't see anything that indicates services can be disabled or deleted automatically. When this happens, I usually have a large backlog of messages in multiple application queues, but nothing extreme. Total message backlog is around 200,000. Does anyone know what might be happening here?

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  • Why should pop() take an argument?

    - by Stephano
    Quick background I'm a Java developer who's been playing around with C++ in my free/bored time. Preface In C++, you often see pop taking an argument by reference: void pop(Item& removed); I understand that it is nice to "fill in" the parameter with what you removed. That totally makes sense to me. This way, the person who asked to remove the top item can have a look at what was removed. However, if I were to do this in Java, I'd do something like this: Item pop() throws StackException; This way, after the pop we return either: NULL as a result, an Item, or an exception would be thrown. My C++ text book shows me the example above, but I see plenty of stack implimentations taking no arguments (stl stack for example). The Qustion How should one implement the pop function in C++? The Bonus Why?

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  • why don't more programming languages have builtin interfaces to the window manager?

    - by Naveen
    Programming is at the heart about automating tasks on a computer. Presumably those tasks would normally be done manually by a human. Humans use the computer through the keyboard, mouse, and interaction with the console or the window manager. But very few languages have built in functions that provide an interface to these basic computing objects. A notable exception is autohotkey, an open source language on windows, providing builtin functions that allow the following simple tasks: * Get Pixel Information * Get mouse position * Keyboard macros * Simulate key strokes * Simulate mouse click * Window management See examples on rosettacode. There have been various attempts on linux, many of which were stopped without explanation. One is the inactive tcl library: android. Search google code for android, lang:tcl

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  • @OneToyMany property null in Entity after (second) merge

    - by iNPUTmice
    Hi, I'm using JPA (with Hibernate) and Gilead in a GWT project. On the server side I have this method and I'm calling this method twice with the same "campaign". On the second call it throws a null pointer exception in line 4 "campaign.getTextAds()" public List<WrapperTextAd> getTextAds(WrapperCampaign campaign) { campaign = em.merge(campaign); System.out.println("getting textads for "+campaign.getName()); for(WrapperTextAd textad: campaign.getTextAds()) { //do nothing } return new ArrayList<WrapperTextAd>(campaign.getTextAds()); } The code in WrapperCampaign Entity looks like this @OneToMany(mappedBy="campaign") public Set<WrapperTextAd> getTextAds() { return this.textads; }

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  • Timespan not accepting day in MVC3

    - by middelpat
    I have a MVC3 application in which i want to set a timespan to for example 2 days and 5 hours. when i enter 02:05:00:00 it gives me the following exception: System.OverflowException: SqlDbType.Time overflow. Value '2.05:00:00' is out of range. Must be between 00:00:00.0000000 and 23:59:59.9999999. When i enter 05:00:00 it correctly saves 5 hours into the database. according to MSDN timespan has a property for days. How do i correctly set the days? Model: public class ProductionTimeVM { [Required] public TimeSpan DefaultTime { get; set; } } In my view i just use: @Html.TextBoxFor(x => x.DefaultTime) For my controller: public ActionResult SaveProductionTime(ProductionTimeVM vm) { ProductionTime productionTime = new ProductionTime(); productionTime.Default = vm.DefaultTime; //some more code } Any idea's?

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  • C# Threading and Sql Connections

    - by Jonathan M
    I have a method that attempts to update a sql server database in an ASP.NET application. If the update fails, it catches the exception and then queues the update in MSMQ, and then spins up a new thread that will later de-queue the pending update and try again. When the thread starts, it fails to open a database connection because it is attempting to connect using Network Service as the login. The sql connection is using Windows Authentication, and will work outside of the thread. If I put a breakpoint in the code that executes inside the new thread and check the Thread.CurrentPrincipal, it shows the Identity as being the correct user. Why is the sql connection attempting to be opened by the Network Service account? I can elaborate further is necessary. Thanks.

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  • Java file delete on NFS drive

    - by RenegadeAndy
    Hey guys. I am trying to delete a file on a NFS drive. I have had other problems manipulating files on remote drives such as moving a file - however i got around it by not using the conventional method i.e renameFile but instead properly using input and output streams. However using the File.delete() returns false , and I have heard suggestions on using the apache commons io FileUtils class - however it just throws an IO exception. Does anybody have any suggestions on a way to delete a file on a network mounted drive using java? Thanks

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  • What's the best way to avoid try...catch...finally... in my unit tests?

    - by Bruce Li
    I'm writing many unit tests in VS 2010 with Microsoft Test. In each test class I have many test methods similar to below: [TestMethod] public void This_is_a_Test() { try { // do some test here // assert } catch (Exception ex) { // test failed, log error message in my log file and make the test fail } finally { // do some cleanup with different parameters } } When each test method looks like this I fell it's kind of ugly. But so far I haven't found a good solution to make my test code more clean, especially the cleanup code in the finally block. Could someone here give me some advices on this? Thanks in advance.

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  • How to find foreign-key dependencies pointing to one record in Oracle?

    - by daveslab
    Hi folks, I have a very large Oracle database, with many many tables and millions of rows. I need to delete one of them, but want to make sure that dropping it will not break any other dependent rows that point to it as a foreign key record. Is there a way to get a list of all the other records, or at least table schemas, that point to this row? I know that I could just try to delete it myself, and catch the exception, but I won't be running the script myself and need it to run clean the first time through. I have the tools SQL Developer from Oracle, and PL/SQL Developer from AllRoundAutomations at my disposal. Thanks in advance!

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  • ASP.NET MVC - how to modify requested URLs?

    - by Marek
    The baidu spider seems to be adding ¤ to end of some crawled urls (it seems that it happens with urls containing single unicode character as the last character) The baidu-requested url looks like this: site.com/abc/ä¤ while site.com/abc/ä is the valid url and as linked from many places on my site. The internal problem is that a different route is matched for this kind of url and an unhandled exception occurs. I would not like to lose baidu because of too many 500 errors on the site. I would like to change the requested URL to a different URL by removing the added character before any ASP.NET MVC processing of the request starts. Can I write a request filter/http module or something similar in ASP.NET MVC to remove the trailing '¤' from the urls? I would not like to alter my routes to counter-hack this behavior.

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  • db2 jdbc driver does not release table locks

    - by as
    situation: We have a web service running on tomcat accessing DB2 database on AS400, we are using JTOPEN drivers for JNDI connections handled by tomcat. For handling transactions and access to database we are using Spring. For each select system takes JDBC connection from JNDI (i.e. from connection pool), does selection, and in the end it closes ResultSet, Statement and releases Connection in that order. That passes fine, shared lock on table dissappears. When we want to do update the same way as we did with select (exception on ResultSet object, we don't have one in such situation), after releasing Connection to JNDI lock on table stays. If we put maxIdle=0 for number of connections in JNDI configuration, this problem disappears, but this degrades performances, we have cca 100 users online on that service, we need few connections to be alive in pool. What do you suggest?

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  • Force IOException during file reading

    - by DixonD
    I have the piece of code that reads data from file. I want to force IOException in this code for testing purpose (I want to check if code throws correct custom exception in this case). Is there a some way to create a file which is protected from being read, for example? Maybe dealing with some security checks can help? Please, note that passing name to not-existent file cannot help, because FileNotFoundException has separate catch clause. Here peace of code for better undestanding of question: BufferedReader reader = null; try { reader = new BufferedReader(new FileReader(csvFile)); String rawLine; while ((rawLine = reader.readLine()) != null) { // some work is done here } } catch (FileNotFoundException e) { throw new SomeCustomException(); } catch (IOException e) { throw new SomeCustomException(); } finally { // close the input stream if (reader != null) { try { reader.close(); } catch (IOException e) { // ignore } } }

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  • android steganography

    - by poo123
    Im doing steganography on android...my code is as below.. public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.src); picw = mBitmap.getWidth(); pich = mBitmap.getHeight(); pix= new int[picw * pich]; mBitmap.getPixels(pix, 0, picw, 0, 0, picw, pich); try { FileOutputStream fos = super.openFileOutput("dest.png", MODE_WORLD_READABLE); mBitmap.compress(CompressFormat.PNG, 100, fos); fos.flush(); fos.close(); }catch (Exception e) { tv.setText(e.getMessage()); } but whenever i save source image with Bitmap.compress() method pix[0] value before and after compression changed..so i'm unable to extract original data...please help me

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  • jprogressbar visible and working on button click

    - by Jisson
    public NewJDialog(java.awt.Frame parent, boolean modal) { super(parent, modal); initComponents(); jProgressBar1.setVisible(false); } private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) { jButton1.setEnabled(false); jProgressBar1.setVisible(true); repaint(); for(int i=0;i<=100;i+=5){ jProgressBar1.setValue(i); // jProgressBar1.setIndeterminate(false); try{ jProgressBar1.paintImmediately(0, 0, 100, 100);//0, 1, 100, 10 Thread.sleep(100); jProgressBar1.setStringPainted(true); }catch(Exception e){} } I use above code for using a Jprogressbar in a JDialog,If I use this I can see a progressbar aftercompleting its process(100 %) and also I want to hide progressbar upto buttonclick.Can any one help me?

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  • Dynamic query to immediate execute?

    - by Curtis White
    I am using the MSDN Dynamic linq to sql package. It allows using strings for queries. But, the returned type is an IQueryable and not an IQueryable<T>. I do not have the ToList() method. How can I this immediate execute without manually enumerating over the IQueryable? My goal is to databind to the Selecting event on a linqtosql datasource and that throws a datacontext disposed exception. I can set the query as the Datasource on a gridview though. Any help greatly appreciated! Thanks. The dynamic linq to sql is the one from the samples that comes with visual studio.

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