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  • Why put a DAO layer over a persistence layer (like JDO or Hibernate)

    - by Todd Owen
    Data Access Objects (DAOs) are a common design pattern, and recommended by Sun. But the earliest examples of Java DAOs interacted directly with relational databases -- they were, in essence, doing object-relational mapping (ORM). Nowadays, I see DAOs on top of mature ORM frameworks like JDO and Hibernate, and I wonder if that is really a good idea. I am developing a web service using JDO as the persistence layer, and am considering whether or not to introduce DAOs. I foresee a problem when dealing with a particular class which contains a map of other objects: public class Book { // Book description in various languages, indexed by ISO language codes private Map<String,BookDescription> descriptions; } JDO is clever enough to map this to a foreign key constraint between the "BOOKS" and "BOOKDESCRIPTIONS" tables. It transparently loads the BookDescription objects (using lazy loading, I believe), and persists them when the Book object is persisted. If I was to introduce a "data access layer" and write a class like BookDao, and encapsulate all the JDO code within this, then wouldn't this JDO's transparent loading of the child objects be circumventing the data access layer? For consistency, shouldn't all the BookDescription objects be loaded and persisted via some BookDescriptionDao object (or BookDao.loadDescription method)? Yet refactoring in that way would make manipulating the model needlessly complicated. So my question is, what's wrong with calling JDO (or Hibernate, or whatever ORM you fancy) directly in the business layer? Its syntax is already quite concise, and it is datastore-agnostic. What is the advantage, if any, of encapsulating it in Data Access Objects?

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  • Why servlet halt a moment in concurrent request.

    - by Hlex
    I use Axis for webservice service. when more than 8 concurrent , there are some request halt randomly for about 30 seconds. I debug by log in every line and found from my code: public class foo{ void bar(){ a(); log.debug('exit from a'); } void a(){ log.debug('exit a'); } the time between "exit a" and "exit from a" are delay about 30 second. This is no reason. I try to increase web container thread pool , heap but didn't help ============== Enviroment websphere 6.1 Spring 2.5 , Hibernate 3 ,Axis 1.6.5 Min heap to 768 Max heap to 1024 Thread pool defult max to 300 Thread pool web container max to 500 ===============

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  • Why can't I publish MVC project

    - by Vnuk
    I'm having problems publishing my MVC project. When I do publish and upload everything to web server I get this: [InvalidOperationException: The view 'Index' or its master could not be found. The following locations were searched: ~/Views/Home/Index.aspx ~/Views/Home/Index.ascx ~/Views/Shared/Index.aspx ~/Views/Shared/Index.ascx] Weird thing is that Index.aspx exists in ~/Views/Home/, but IIS cannot find it there. If I copy entire project to web server and let asp.net compile it on the fly it works like a charm. My routing code: routes.MapRoute( _ "Default", _ "{controller}/{action}/{id}", _ New With {.controller = "Home", .action = "Index", .id = ""} _ ) routes.MapRoute("Root", "", New With {.controller = "Home", .action = "Index", .id =""}) I'm using IIS7 on Windows 2008 Web server. ASP.NET MVC 1.0, Visual Studio 2008. I've tried it local with IIS7 on Windows 7 - same error.

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  • Why release the NSURLConnection instance in this statement?

    - by aquaibm
    I read this in a book. -(IBAction) updateTweets { tweetsView.text = @""; [tweetsData release]; tweetsData = [[NSMutableData alloc] init]; NSURL *url = [NSURL URLWithString:@"http://twitter.com/statuses/public_timeline.xml" ]; NSURLRequest *request = [[NSURLRequest alloc] initWithURL: url]; NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self]; [connection release]; [request release]; [activityIndicator startAnimating]; } In this statement,is that correct to release the "connection" instance at that time? After releasing it which means this NSURLConnection instance will be destroyed since it's reference count is 0 ,how are we going to make this connection operation work? THANKS.

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  • Tortoise SVN Icon Overlays Displaying Everywhere...Why?

    - by jwalkerjr
    Update: So, this turns out to have nothing to do with Tortoise SVN. I use Mozy.com for off-site backups and their new version includes these icon overlays. They can be disabled via the config options...or see here http://forum.pcmech.com/showthread.php?p=1385433. Thanks @OS for the answer. Been using Tortoise SVN for some time on my Vista box. Within the last few days (and after recently upgrading to 1.5.4) the icon overlays are displaying on all files. My exclude path is: * My include paths are: C:\Users\jw\Documents\Visual Studio 2008\Projects\SVNProjects* C:\Users\jw\Documents\VB Projects\SVNProjects* I haven't touched those settings in months. Any ideas? Help. Thanks.

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  • Why LINQ will work this way?

    - by Benny
    public static ArrayList GetStudentAsArrayList() { ArrayList students = new ArrayList { new Student() { RollNumber = 1,Name ="Alex " , Section = 1 ,HostelNumber=1 }, new Student() { RollNumber = 2,Name ="Jonty " , Section = 2 ,HostelNumber=2 }, }; return students; } this doesn't compile: ArrayList is not IEnumerable ArrayList lstStudents = GetStudentAsArrayList(); var res = from r in lstStudents select r; but this will compile: ArrayList lstStudents = GetStudentAsArrayList(); var res = from Student r in lstStudents select r; Can anybody explain? what's the magic here?

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  • Why encodeXxx methods in UIComponent accept FacesContext parameter?

    - by Roman
    I haven't ever before created custom component in jsf so I've noticed it only now that methods like encodeBegin(), encodeEnd() etc accept FacesContext parameter. FacesContext instance can usually be received with FacesContext.getCurrentInstance(). So, I wonder whether these methods have FacesContext parameter just for convenience or some different objects can be passed there (maybe from external resources..). If the latter is possible then could you give an example pls.

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  • Why is an inverse loop faster than a normal loop (test included)

    - by Saif Bechan
    I have been running some small tests in PHP on loops. I do not know if my method is good. I have found that a inverse loop is faster than a normal loop. I have also found that a while-loop is faster than a for-loop. Setup <?php $counter = 10000000; $w=0;$x=0;$y=0;$z=0; $wstart=0;$xstart=0;$ystart=0;$zstart=0; $wend=0;$xend=0;$yend=0;$zend=0; $wstart = microtime(true); for($w=0; $w<$counter; $w++){ echo ''; } $wend = microtime(true); echo "normal for: " . ($wend - $wstart) . "<br />"; $xstart = microtime(true); for($x=$counter; $x>0; $x--){ echo ''; } $xend = microtime(true); echo "inverse for: " . ($xend - $xstart) . "<br />"; echo "<hr> normal - inverse: " . (($wend - $wstart) - ($xend - $xstart)) . "<hr>"; $ystart = microtime(true); $y=0; while($y<$counter){ echo ''; $y++; } $yend = microtime(true); echo "normal while: " . ($yend - $ystart) . "<br />"; $zstart = microtime(true); $z=$counter; while($z>0){ echo ''; $z--; } $zend = microtime(true); echo "inverse while: " . ($zend - $zstart) . "<br />"; echo "<hr> normal - inverse: " . (($yend - $ystart) - ($zend - $zstart)) . "<hr>"; echo "<hr> inverse for - inverse while: " . (($xend - $xstart) - ($zend - $zstart)) . "<hr>"; ?> Average Results The difference in for-loop normal for: 1.0908501148224 inverse for: 1.0212800502777 normal - inverse: 0.069570064544678 The difference in while-loop normal while: 1.0395669937134 inverse while: 0.99321985244751 normal - inverse: 0.046347141265869 The difference in for-loop and while-loop inverse for - inverse while: 0.0280601978302 Questions My question is can someone explain these differences in results? And is my method of benchmarking been correct?

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  • Why does this gstreamer pipeline stall ?

    - by timday
    I've been playing around with gstreamer pipelines using gst-launch. I don't have any problems if I just want to process audio or video separately (to separate files, or to alsasink/ximagesink), but I'm confused by what I need to do to mux the streams back together using, say avimux. This gst-launch-0.10 filesrc location=MVI_2034.AVI ! decodebin name=dec \ dec. ! queue ! audioconvert ! 'audio/x-raw-int,rate=44100,channels=1' ! queue ! mux. \ dec. ! queue ! videoflip 1 ! ffmpegcolorspace ! jpegenc ! queue ! mux. \ avimux name=mux ! filesink location=out.avi just outputs Setting pipeline to PAUSED ... Pipeline is PREROLLING ... and then stalls indefinitely. What's the trick ?

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  • Why packets injected with libpcap are duplicated?

    - by r0u1i
    I'm using sharppcap in order to send packets as part of a monitoring system. Usually it works well but I've encountered the strangest bug on a hosted vista machine and I would like your help. On that virtual vista machine, injected packets are duplicated. That is, if I send a ping request using libpcap, it somehow gets duplicated and I get two requests on the destination machine. The two requests are almost identical byte-wise, and the only difference between them is that the second packet's TTL field is one minus the original packet's value. Using wireshark I can see the packet gets duplicated before it (and its clone) leave the vista machine. The problem is manifested even when using other tools for injecting packets using libpcap (namely PlayCap). Any ideas?

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  • Why isn't this javascript code working?

    - by DarkLightA
    http://jsfiddle.net/LU3pE/ I want the function to make the arguments into a single string and return it. What have I done incorrectly? function cooncc(divider, lastdiv){ var returner; for (var i = 0; i < (arguments.length - 2); i++) { returner += arguments[i+2] + divider; } returner -= divider; returner += lastdiv + arguments[arguments.length - 1]; return divider; } var output = cooncc(", ", ", and ", "Andy", "Becky", "Caitlin", "Dave", "Erica", "Fergus", "Gaby"); document.body.innerHTML = "<h1>" + output + ".</h1>";

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  • Why do switch statements continue after case

    - by John W.
    After evaluating a case in a switch statement in Java (and I am sure other languages) the following case's are also evaluated unless a control statement like break, or return is used. I understand this is probably an implementation detail, but what is/are the reasons for having this functionality happen? Thanks!

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  • Why can't my master page be loaded

    - by Irwin
    I've largely ignored this error, but i can do so no more. I'm trying to view a page that inherits from a master page in my solution, but I see this: "The Master Page file 'Site.master' cannot be loaded." The page exists, I can browse to it, view it in design view and do stuff. When the site is loaded in the browser, it works fine. Any ideas?

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  • Why is this static routing not working ?

    - by geeko
    Greeting gurus, I'm trying to develop a DHCP enforcement extension like Microsoft NAP. My trick to block dynamic-IP requesting machines (that don't meet certain policy) is to strip the default gateway (no default gateway) stated in the IP lease and set the lease subnet mask to 255.255.255.255. Now I need the blocked machines to be able to reach some specific locations (IPs) on the network. To allow for this, I'm including some static routes in the lease. For example, I'm including 10.10.10.11 via router 10.10.10.254 (the one to which the blocked machine that needs to access 10.10.10.11 is connected). Unfortunately, as soon as I set the default gateway to nothing, blocked machines cannot reach any of the added static routes. I also tried classless static routes. Any ideas ? any one knows how MS NAP actually do it ? Geeko

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  • Why does the textField not show up when I change the defaultTextFormat

    - by Leon
    I have an if/else statement which checks the length of my current title, and then is suppose to change the defaultTextFormat of the title textField and set the text. Currently the title will not show up now, no matter what character length the title is, any thoughts on what I could be doing wrong here? public function switchTitle(sentText):void { titleString = sentText; trace("---------"+"\n"); trace("Forumula testing"); trace("titleString = "+titleString); trace("titleString.length = "+titleString.length); trace("titleSize/10 = "+(titleSize/10)); trace("\n"); // If Title can fit: if (titleString.length < (titleSize/10)) { vTitle.defaultTextFormat = Fonts.VideoTitle; titleString = sentText; // If Title can't fit: } else if (titleString.length >= (titleSize/10)) { vTitle.defaultTextFormat = Fonts.VideoTitle2; titleString = sentText; } trace("---------"+"\n"); //vTitle.text = titleString; // <-- Original code, worked }

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  • Learning Lisp - Why ?

    - by David
    I really feel that I should learn Lisp and there are plenty of good resources out there to help me do it. I'm not put off by the complicated syntax, but where in "traditional commercial programming" would I find places it would make sense to use it instead of a procedural language. Is there a commercial killer-app out there that's been written in Lisp ?

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  • Why do calls to waveOutGetPosition hang?

    - by MusiGenesis
    I'm using the winmm.dll API method waveOutGetPosition to get the current position of the playback of a WAV file. Sometimes this works as expected for me, but eventually one of the calls never returns and my application locks up. I found this thread with a few users who have experienced the same problem: http://social.msdn.microsoft.com/Forums/en-US/windowsgeneraldevelopmentissues/thread/c6a1e80e-4a18-47e7-af11-56a89f638ad7 but no solution. Has anyone run into this problem before?

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  • Why my shell program wont open the file got as argument in function "cat"

    - by anna karenina
    I included the code below, sorry to bother you with so much code. Argument parsing is ok, i checked it out with watches. I've put some printfs to check out where the problem may be and it seems that it wont open the file cat receives as argument. i called from shell like "cat -b file" #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <string.h> #define TRUE 0 #define FALSE 1 void yes(int argc, char *argv[]); int cat(int argc, char *argv[]); //#include "cat.h" //#include "yes.h" //#include"tee.h" char buf[50],c[10], *p2,*p, *pch; int count; char *matrix[20]; void yes(int argc, char *argv[]) { int i; // if (argc >= 2 && *argv[1] == '-') // { //printf("ERROR!"); //} //if (argc == 1) // { while (1) if (puts("y") == EOF) { perror("yes"); exit(FALSE); } // } while (1) for (i = 1; i < argc; i++) if (fputs(argv[i], stdout) == EOF || putchar(i == argc - 1 ? '\n' : ' ') == EOF) { perror("yes"); exit(FALSE); } //exit(TRUE); } int main(int argc, char *argv[]) { //p=(char *)malloc(sizeof(char)*50); do { fprintf (stderr, "$ "); fgets (buf,50,stdin); p=buf; fprintf (stderr, "Comanda primita de la tastatura: "); fputs (buf, stderr); int i=0,j=0; //strcpy(p,buf); strcpy(c,"\0"); while (buf[i] == ' ') { i++; p++; } if (buf[i] == '#') fprintf (stderr, "Nici o comanda, ci e un comentariu!\n"); else { j=0; while (buf[i] != ' ' && buf[i] != '\n') { i++; j++; } strncpy (c,p,j); fprintf (stderr, "%s\n",c); if (strcmp (c,"yes") == 0) { p2 = p+j+1; pch = strtok (p2," "); count = 0; while (pch != NULL) { //printf ("%s\n",pch); matrix[count] = strdup(pch); pch = strtok (NULL, " "); count++; } yes(count, matrix); fprintf (stderr, "Aici se va executa comanda yes\n"); } else if (strcmp (c,"cat") == 0) { p2 = p+j+1; pch = strtok (p2," "); count = 0; while (pch != NULL) { //printf ("%s\n",pch); matrix[count] = strdup(pch); pch = strtok (NULL, " "); count++; } cat(count,matrix); fprintf (stderr, "Aici se va executa comanda cat \n"); } else if (strcmp (c,"tee") == 0) { //tee(); fprintf(stderr, "Aici se va executa comanda tee\n"); } fprintf (stderr, "Aici se va executa comanda basename\n"); strcpy(buf,"\0"); } } while (strcmp(c, "exit") != 0); fprintf (stderr, "Terminat corect!\n"); return 0; } int cat(int argc, char *argv[]) { int c ; opterr = 0 ; optind = 0 ; char number = 0; char squeeze = 0; char marker = 0; fprintf(stderr,"SALUT< SUNT IN FUNCTIZE>\n"); while ((c = getopt (argc, argv, "bnsE")) != -1) switch (c) { case 'b' : number = 1; break; case 'n' : number = 2; break; case 'm' : marker = 1; break; case 's' : squeeze = 1; break; case 'E' : marker = 1; break; } if (optind + 1 != argc) { fprintf (stderr, "\tWrong arguments!\n") ; return -1 ; } FILE * fd = fopen (argv[optind], "r"); printf("am deschis fisierul %s ",argv[optind]); if (fd == NULL) { printf("FISIER NULL asdasdasdasdasd"); return 1; } char line[1025]; int line_count = 1; while (!feof(fd)) { fgets(line, 1025, fd); printf("sunt in while :> %s",line); int len = strlen(line); if (line[len - 1] == '\n') { if(len - 2 >= 0) { if(line[len - 2] == '\r') { line[len - 2] = '\0'; len -= 2; } else { line[len - 1] = '\0'; len -= 1; } } else { line[len - 1] = '\0'; len -= 1; } } if (squeeze == 1 && len == 0) continue; if (number == 1) { fprintf (stdout, "%4d ", line_count); line_count++; } else if (number == 2) { if (len > 0) { fprintf (stdout, "%4d ", line_count); line_count++; } else fprintf (stdout, " "); } fprintf(stdout, "%s", line); if (marker == 1) fprintf(stdout, "$"); fprintf(stdout, "\n"); } fclose (fd); return 0 ; }

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  • why custom state won't work with compound drawable?

    - by schwiz
    Hello I am trying to make a password registration widget that will show a little checkbox in the textbox when both password boxes match. I decided to go about this by extending EditText to implement a valid and an empty state and then just use a state-list drawable to handle everything else. I followed the same method that the CompoundButton uses to add a custom state and everything seems to be right but the image will never change no matter what the state is (custom state or even state_focused etc) Is there some reason that the compound drawables of a TextView wouldn't work as a state-list drawable? Or, am I doing something wrong? Here is attrs.xml <resources> <declare-styleable name="ValidyState"> <attr name="state_valid" format="boolean"/> <attr name="state_has_text" format="boolean"/> </declare-styleable> </resources> my selector <selector xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res/com.schwiz.test"> <item android:drawable="@drawable/emptyspace" app:state_has_text="false"/> <item android:drawable="@drawable/ic_valid" app:state_valid="true" app:state_has_text="true"/> <item android:drawable="@drawable/ic_invalid" app:state_valid="false" app:state_has_text="true"/> </selector> and in my overridden EditText class private static final int[] VALID_STATE_SET = { R.attr.state_valid }; private static final int[] HASTEXT_STATE_SET = { R.attr.state_has_text }; ... private void refreshDrawables(){ Drawable[] drawables = getCompoundDrawables(); for(int i = 0; i < drawables.length; i++){ if(drawables[i] != null) { drawables[i].setState(getDrawableState()); } } invalidate(); } @Override protected void drawableStateChanged() { super.drawableStateChanged(); refreshDrawables(); } @Override protected int[] onCreateDrawableState(int extraSpace) { final int[] drawableState = super.onCreateDrawableState(extraSpace + 2); if(hasText){ mergeDrawableStates(drawableState, HASTEXT_STATE_SET); } if(isValid){ mergeDrawableStates(drawableState, VALID_STATE_SET); } return drawableState; }

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  • Why build Javascript functions as JQuery plugins?

    - by Mohammad
    I've seen alot of JQuery implementations of existent JavaScript functions that merely wrap the JavaScript code in a JQuery wrapper and don't actually rely on any of JQuery's base for their operation. What are the benefits of using Javascript as a JQuery plugin? If there are none is there a speed loss to use a JQuery plugin that could have easily been implemented outside the wrapper just as well? Many thanks in advance (just trying to learn something here).

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  • Why is this codes output an Error?

    - by Ari Susanto
    I am a newbie on php writing. In the my first trying, I get a problem on input a html tag to php. This code output an error: <?php $a="Begin"; $b=12; echo $b . " " . $a . " " . "This is php file <br/>"; echo strlen($a); echo strpos($a,"in") . "<br/>"; echo addcslashes($a,"i")"; ?> this is the error message I get: Parse error: syntax error, unexpected '"', expecting ',' or ';' in /home/specials/public_html/bextool.com/1.php on line 7 Is there any body who can explain about it?

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  • Why is postgresql update query so slow sometimes, even with index

    - by Matija
    i have a simple update query (foo column type is BOOLEAN (default false)): update tablename set foo = true where id = 234; which "id" is set to (primary) key, and if i run "explain analyze" i got: Index Cond: (id = 234) Total runtime: 0.358 ms but still, i have plenty of unexplained queries at slow log (pgfouine), which took more than 200s (?!): Times executed: 99, Av. duration (s): 70 can anyone please explain, whats the reason for that? (1.5 mio rows in table, postgresql 8.4)

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