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  • ejb timer service vs cron

    - by darko petreski
    Hi Ejb timer service can start some process in desired time intervals. Also we can do the same thing with cron (min 1 minute) interval. But doing it with cron we have more power on controlling, monitoring and changing the intervals. Also we can restart if needed the cron very easily by command line. Also we can add or remove lines in the cron transparently. What are the advantages of using ejb timer services over calling the ejbs from cron ? (several lines of code in the cron classes are not a problem) Regards.

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  • Traditional IO vs memory-mapped

    - by Senne
    I'm trying to illustrate the difference in performance between traditional IO and memory mapped files in java to students. I found an example somewhere on internet but not everything is clear to me, I don't even think all steps are nececery. I read a lot about it here and there but I'm not convinced about a correct implementation of neither of them. The code I try to understand is: public class FileCopy{ public static void main(String args[]){ if (args.length < 1){ System.out.println(" Wrong usage!"); System.out.println(" Correct usage is : java FileCopy <large file with full path>"); System.exit(0); } String inFileName = args[0]; File inFile = new File(inFileName); if (inFile.exists() != true){ System.out.println(inFileName + " does not exist!"); System.exit(0); } try{ new FileCopy().memoryMappedCopy(inFileName, inFileName+".new" ); new FileCopy().customBufferedCopy(inFileName, inFileName+".new1"); }catch(FileNotFoundException fne){ fne.printStackTrace(); }catch(IOException ioe){ ioe.printStackTrace(); }catch (Exception e){ e.printStackTrace(); } } public void memoryMappedCopy(String fromFile, String toFile ) throws Exception{ long timeIn = new Date().getTime(); // read input file RandomAccessFile rafIn = new RandomAccessFile(fromFile, "rw"); FileChannel fcIn = rafIn.getChannel(); ByteBuffer byteBuffIn = fcIn.map(FileChannel.MapMode.READ_WRITE, 0,(int) fcIn.size()); fcIn.read(byteBuffIn); byteBuffIn.flip(); RandomAccessFile rafOut = new RandomAccessFile(toFile, "rw"); FileChannel fcOut = rafOut.getChannel(); ByteBuffer writeMap = fcOut.map(FileChannel.MapMode.READ_WRITE,0,(int) fcIn.size()); writeMap.put(byteBuffIn); long timeOut = new Date().getTime(); System.out.println("Memory mapped copy Time for a file of size :" + (int) fcIn.size() +" is "+(timeOut-timeIn)); fcOut.close(); fcIn.close(); } static final int CHUNK_SIZE = 100000; static final char[] inChars = new char[CHUNK_SIZE]; public static void customBufferedCopy(String fromFile, String toFile) throws IOException{ long timeIn = new Date().getTime(); Reader in = new FileReader(fromFile); Writer out = new FileWriter(toFile); while (true) { synchronized (inChars) { int amountRead = in.read(inChars); if (amountRead == -1) { break; } out.write(inChars, 0, amountRead); } } long timeOut = new Date().getTime(); System.out.println("Custom buffered copy Time for a file of size :" + (int) new File(fromFile).length() +" is "+(timeOut-timeIn)); in.close(); out.close(); } } When exactly is it nececary to use RandomAccessFile? Here it is used to read and write in the memoryMappedCopy, is it actually nececary just to copy a file at all? Or is it a part of memorry mapping? In customBufferedCopy, why is synchronized used here? I also found a different example that -should- test the performance between the 2: public class MappedIO { private static int numOfInts = 4000000; private static int numOfUbuffInts = 200000; private abstract static class Tester { private String name; public Tester(String name) { this.name = name; } public long runTest() { System.out.print(name + ": "); try { long startTime = System.currentTimeMillis(); test(); long endTime = System.currentTimeMillis(); return (endTime - startTime); } catch (IOException e) { throw new RuntimeException(e); } } public abstract void test() throws IOException; } private static Tester[] tests = { new Tester("Stream Write") { public void test() throws IOException { DataOutputStream dos = new DataOutputStream( new BufferedOutputStream( new FileOutputStream(new File("temp.tmp")))); for(int i = 0; i < numOfInts; i++) dos.writeInt(i); dos.close(); } }, new Tester("Mapped Write") { public void test() throws IOException { FileChannel fc = new RandomAccessFile("temp.tmp", "rw") .getChannel(); IntBuffer ib = fc.map( FileChannel.MapMode.READ_WRITE, 0, fc.size()) .asIntBuffer(); for(int i = 0; i < numOfInts; i++) ib.put(i); fc.close(); } }, new Tester("Stream Read") { public void test() throws IOException { DataInputStream dis = new DataInputStream( new BufferedInputStream( new FileInputStream("temp.tmp"))); for(int i = 0; i < numOfInts; i++) dis.readInt(); dis.close(); } }, new Tester("Mapped Read") { public void test() throws IOException { FileChannel fc = new FileInputStream( new File("temp.tmp")).getChannel(); IntBuffer ib = fc.map( FileChannel.MapMode.READ_ONLY, 0, fc.size()) .asIntBuffer(); while(ib.hasRemaining()) ib.get(); fc.close(); } }, new Tester("Stream Read/Write") { public void test() throws IOException { RandomAccessFile raf = new RandomAccessFile( new File("temp.tmp"), "rw"); raf.writeInt(1); for(int i = 0; i < numOfUbuffInts; i++) { raf.seek(raf.length() - 4); raf.writeInt(raf.readInt()); } raf.close(); } }, new Tester("Mapped Read/Write") { public void test() throws IOException { FileChannel fc = new RandomAccessFile( new File("temp.tmp"), "rw").getChannel(); IntBuffer ib = fc.map( FileChannel.MapMode.READ_WRITE, 0, fc.size()) .asIntBuffer(); ib.put(0); for(int i = 1; i < numOfUbuffInts; i++) ib.put(ib.get(i - 1)); fc.close(); } } }; public static void main(String[] args) { for(int i = 0; i < tests.length; i++) System.out.println(tests[i].runTest()); } } I more or less see whats going on, my output looks like this: Stream Write: 653 Mapped Write: 51 Stream Read: 651 Mapped Read: 40 Stream Read/Write: 14481 Mapped Read/Write: 6 What is makeing the Stream Read/Write so unbelievably long? And as a read/write test, to me it looks a bit pointless to read the same integer over and over (if I understand well what's going on in the Stream Read/Write) Wouldn't it be better to read int's from the previously written file and just read and write ints on the same place? Is there a better way to illustrate it? I've been breaking my head about a lot of these things for a while and I just can't get the whole picture..

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  • VS 2010 Layer Diagram Validation Error is Showing A Dependency That Doesn't Even Exist (AV0001)

    - by Dan
    I'm getting the following validation error on my layer diagram Error 65 AV0001 : Invalid Dependency : Weld.Interface.Core(Assembly) -- Weld.Interface(Namespace) Layers: Application Framework Core, Application Framework | Dependencies: Namespace Reference D:\Projects\Windows Projects\Weld\Weld\ModelingProject1\Weld.layerdiagram 0 0 ModelingProject1 Weld.Interface.Core: This assembly and namespace does not have a reference to Weld.Interface and only references .NET Framework classes Weld.Interface: This assembly and namespace does not have a reference to Weld.Interface There is no dependancy between these two layers in the dependency diagram. I am confused why I am getting this error. No dependency in the project or code, and no dependency is even setup in the layer diagram. Somehow the Validation logic in the layer diagram is seeing a non existant dependency and saying it is an error. Any ideas what either I might have missed or what is causing this problem?

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  • DataTable vs. Collection in .Net

    - by B Pete
    I am writing a program that needs to read a set of records that describe the register map of a device I need to communicate with. Each record will have a handfull of fields that describe the properties of each register. I don't really need to edit or modify the data in my VB or C# program, though I would like to be able to display the data on a grid. I would like to store the data in a CSV file, or perhaps an XML file. I need to enable users to edit the data off-line, preferably in excel. I am considering using a DataTable or a Collection of "Register" objects (which I would define). I prototyped a DataTable, and found I can read/write XML easily using the built in methods and I can easily bind to a DataGridView. I was not able to find a way to retreive info on a single register without using a query that returns a collection of rows, even though I defined a unique primaty key column. The syntax to get a value from a column is also complex, though I could be missing something on both counts. I'm tempted to use a collection of "Register" objects that I can access via a unique key. It would be a little more coding up front, but seems like a cleaner solution overall. I should still be able to use LINQ to dataset to query subsets of registers when I need them, but would also be able to grab a single field using a the key value, something like this: Registers(keyValue).fieldName). Which would be a cleaner approach to the problem? Is there a way to read/write XML into a Collection without needing custom code? Could this be accomplished using String for a key?

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  • Does someone have used Network Emulator API exposed in VS 2010

    - by Pritam
    Hi, I have seen VS2010 exposing Network Emulator API. I have installed it and trying to use this API, but not able detect whether it is really running with this code or not. Sometime I have given wrong profile name but it does not throw any error. Please find below my piece of code. If some one have used it please help me. IntPtr m_emulatorHandle = IntPtr.Zero; NetworkEmulationApi.LoadProfile(m_emulatorHandle, "300KB_WithLatency.xml"); NetworkEmulationApi.StartEmulation(m_emulatorHandle); Thanks, Pritam

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  • DataGridTemplateColumn for individual control-column vs DataGridTextColumn

    - by msfanboy
    Hello, what is the difference, both works: DataGridTemplateColumn versus DataGridTextColumn <DataGridTemplateColumn Header="Homework"> <DataGridTemplateColumn.CellTemplate> <DataTemplate> <RichTextBox > <FlowDocument> <Paragraph> <Run Text="{Binding Homework}"/> </Paragraph> </FlowDocument> </RichTextBox> </DataTemplate> </DataGridTemplateColumn.CellTemplate> </DataGridTemplateColumn> <DataGridTextColumn Header="Homework"> <DataGridTextColumn.CellTemplate> <DataTemplate> <RichTextBox > <FlowDocument> <Paragraph> <Run Text="{Binding Homework}"/> </Paragraph> </FlowDocument> </RichTextBox> </DataTemplate> </DataGridTextColumn.CellTemplate> </DataGridTextColumn >

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  • resharper "cleanup code" vs. 'var' keyword

    - by bitbonk
    I have an odd behavior with code clean up for c# in visual studio 2008 Team Developer Edition. Whenever I clean up my code using "Full Cleanup" it replaces all var declaration with explicit type declarations. But I have set the appropriate settings under "Inspection Severity" "Use var keyword when initializer explictly declares type" and "use var keyword when possible" to "Show as Error" Is there any other setting I need to set or is this a known bug?

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  • LINQ: Dot Notation vs Query Expression

    - by Martín Marconcini
    I am beginning to use LINQ in general (so far toXML and toSQL). I've seen that sometimes there are two or more ways to achieve the same results. Take this simple example, as far as I understand both return exactly the same thing: SomeDataContext dc = new SomeDataContext(); var queue = from q in dc.SomeTable where q.SomeDate <= DateTime.Now && q.Locked != true orderby (q.Priority, q.TimeCreated) select q; var queue2 = dc.SomeTable .Where( q => q.SomeDate <= DateTime.Now && q.Locked != true ) .OrderBy(q => q.Priority) .ThenBy(q => q.TimeCreated); Besides any mistake I may have made in the syntax or a missing parameter or difference, the idea is that there are two ways to express the same thing; I understand that the first method has some limitations and that the "dot notation" is more complete, but besides that, are there any other advantages?

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  • Portable C++ library for IPC (processes and shared memory), Boost vs ACE vs Poco?

    - by user363778
    Hi, I need a portable C++ library for doing IPC. I used fork() and SysV shared memory until now but this limits me to Linux/Unix. I found out that there are 3 major C++ libraries that offer a portable solution (including Windows and Mac OS X). I really like Boost, and would like to use it but I need processes and it seems like that this is only an experimental branch until now!? I have never heard of ACE or POCO before and thus I am stuck I do not know which one to choose. I need fork(), sleep() (usleep() would be great) and shared memory of course. Performance and documentation are also important criteria. Thanks, for your Help!

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  • NSPredicate error/behaving differently on 10.5 vs 10.6

    - by Tristan
    I am using a NSPredicate to determine if an entered email address is valid. On 10.6 it works perfectly as expected. I recently decided to get my app going on 10.5 and this is the only thing that doesn't work. The error i get is as follows: "Can't do regex matching, reason: Can't open pattern U_MALFORMED_SET (string [email protected], pattern ([\w-+]+(?:\.[\w-+]+)*@(?:[\w-]+\.)+[a-zA-Z]{2,7}), case 0, canon 0)" The code im using is as follows: NSString *regex = @"([\\w-+]+(?:\\.[\\w-+]+)*@(?:[\\w-]+\\.)+[a-zA-Z]{2,7})"; NSPredicate *regextest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex]; if ([regextest evaluateWithObject:[userEmail objectValue]] == YES) Does anyone know why this isn't working on 10.5? And how I might get it working or be able to do this test in a way compatible for both 10.5 and 10.6?

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  • Penalty of using QGraphicsObject vs QGraphicsItem?

    - by Dutch
    I currently have a hierarchy of items based off of QGraphicsItem. I want to move to QGraphicsObject instead so that I can put properties on my items. I will not be making use of signals/slots or any other features of QObject. I'm told that you shouldn't derive from QObject because it's "heavy" and "slow". To test the impact, I derive from QGraphicsObject, add a couple properties to my items, and look at the memory usage of the running app. I create 1000 items using both flavors and I don't notice anything more than 10k more memory usage. Since all I am adding on to my items are properties, is it safe to say that QObject only adds weight if you are using signals/slots?

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  • Flash video player VS HTML 5 Video.....

    - by metal-gear-solid
    I need to add a video player to play a video on a webpage. usually i use Flash player with the help of swfobject library. which works if flash player and javascript both are enabled. I'm currently using XHTML 1.0 strict doctype. My question is can i just change my doctype to HTML 5 doctype and add Video player using HTML 5 video. for browser which do not support HTML5 i can a a javascript. in this condition in supported browser Video will work without Flash player and javascript and in non-supported browser will work with js support. Is this possible? Is this a good idea?

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  • Merits of .NET ORM data access methods Enity Framework vs. NHibernate vs. Subsonic vs. ADO.NET Datas

    - by Lloyd
    I have recently heard "fanboys" of different .NET ORM methodologies express strong, if not outlandish oppinions of other ORM methodologies. And frankly feel a bit in the dark. Could you please explain the key merits of each of these .NET ORM solutions? Entity Framework NHibernate Subsonic ADO.NET Datasets I have a good understanding of 1&4, and a cursory understanding of 2&3, but apparently not enough to understand the implied cultural perceptions of one towards the other.

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  • 301 redirect vs parking

    - by Pat
    I have several domain names registered, each a slight variant of each other. E.g, fastcar.com fast-car.com fastcar.co.uk fast-car.co.uk etc.. I don't wish to be penalized for duplicate content or spammy links by any of the major search engines. Should I park them all directly on the main domain I wish to promote, 301 redirect them to the main domain or not use them at all? Thanks

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  • Concepts: Channel vs. Stream

    - by hotzen
    Hello, is there a conceptual difference between the terms "Channel" and "Stream"? Do the terms require/determine, for example, the allowed number of concurrent Consumers or Producers? I'm currently developing a Channel/Stream of DataFlowVariables, which may be written by one producer and read by one consumer as the implementation is destructive/mutable. Would this be a Channel or Stream, is there any difference at all? Thanks

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  • Throw a long list of exceptions vs throw an Exception vs throw custom exception?

    - by athena
    I have an application which uses two methods of an API. Both these methods throw more than five exceptions each. So, if I just add a throws declaration then it becomes a list of more than ten. (My method cannot handle any of the ten exceptions) I have read that throwing a long list of exceptions is a bad practice. Also throwing (the umbrella) Exception is a bad practice. So, what should I do? Add a try catch block, and log and exit in the catch block? (Current approach) Create a custom exception class, wrap every exception and throw the custom exception? Add a throws declaration for all exceptions? Throw Exception?

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  • Parameterized SQL statements vs. very simple method

    - by Philipp G
    When I started to write the first SQL-Statements in my programs I felt quite comfortable with protecting myself against SQL-Injection with a very simple method that a colleague showed me. It replaced all single quotes with two single quotes. So for example there is a searchfield in which you can enter a customername to search in the customertable. If you would enter Peter's Barbershop The SELECT Statement would look like SELECT * FROM Customers WHERE Customername = 'Peter''s Barbershop' If now an attacker would insert this: ';DROP TABLE FOO; -- The statement would look like: SELECT * FROM Customers WHERE Customername = ''';DROP TABLE FOO;--' It would not drop any table, but search the customertable for the customername ';DROP TABLE FOO;-- which, I suppose, won't be found ;-) Now after a while of writing statements and protecting myself against SQL-Injection with this method, I read that many developers use parameterized statements, but I never read an article where "our" method was used. So definitely there is a good reason for it. What scenarios would parameterized statements cover but our method doesn't? What are the advantages of parameterized statements compared to our method? Thanks Philipp

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