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• Aquatic Prime on 10.6?

  - by Kevin

  Hello, I have 2 applications that I use with Aquatic Prime. One is an application just with the Aquatic Prime framework, and the other is an application that I've been working on that has been incorporated with the Aquatic Prime framework. The first application I mentioned before has its SDK set to 10.5 with the architecture to 32-bit. The second application I made has its SDK that is set to 10.6 (which it has to since I need NSRunningApplication) and its architecture to 32-bit. Now my question is, whenever I debug my first application it works perfectly fine, but with my second it gives me this interrupted error right after Running. What's going wrong? I've tried doing some breakpoints like "objc-exception-throw" but all it says is stopped at breakpoint 1. I need 10.6 in my application, but I also need Aquatic Prime. Can anyone help me solve this problem? Ok here's the one from the stack trace which I have no idea how to read: 0x91cdff11 <+0000> push %ebp 0x91cdff12 <+0001> mov %esp,%ebp 0x91cdff14 <+0003> sub $0x28,%esp 0x91cdff17 <+0006> mov %ebx,-0xc(%ebp) 0x91cdff1a <+0009> mov %esi,-0x8(%ebp) 0x91cdff1d <+0012> mov %edi,-0x4(%ebp) 0x91cdff20 <+0015> call 0x91cdff25 <objc_exception_throw+20> 0x91cdff25 <+0020> pop %ebx 0x91cdff26 <+0021> mov 0x8(%ebp),%esi 0x91cdff29 <+0024> lea 0xe4cbb8b(%ebx),%edi 0x91cdff2f <+0030> mov 0x4(%edi),%eax 0x91cdff32 <+0033> test %eax,%eax 0x91cdff34 <+0035> jne 0x91cdff3b <objc_exception_throw+42> 0x91cdff36 <+0037> call 0x91ce4f53 <set_default_handlers> 0x91cdff3b <+0042> mov %esi,(%esp) 0x91cdff3e <+0045> nop 0x91cdff3f <+0046> nopl 0x0(%eax) 0x91cdff43 <+0050> mov %esi,(%esp) 0x91cdff46 <+0053> call *0x4(%edi) 0x91cdff49 <+0056> lea 0xfd44(%ebx),%eax 0x91cdff4f <+0062> mov %eax,(%esp) 0x91cdff52 <+0065> call 0x91ce4e1f <_objc_fatal> The the GDB tells me its all good: run [Switching to process 990] Running… 2009-10-14 15:20:33.233 ApplicationName[990:a0f] init Sincerely, Kevin

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• Problems with CGI wrapper for PHP

  - by user205878

  I'm having a bugger of a time with a CGI wrapper for PHP. I know very little about CGI and PHP as CGI. Here's what I know about the system: Solaris 10 on a 386 Suhosin PHP normally running as CGI, with cgiwrap (http://cgiwrap.sourceforge.net/). I am not able to find an example wrapper.cgi on the server to look at. Shared hosting (virtual host), so I don't have access to Apache config. But the admins are not helpful. Switching hosts is not an option. Options directive cannot be overridden in .htaccess (ExecCGI, for example). .htaccess: AddHandler php-handler .php Action php-handler "/bin/test.cgi" ~/public_html/bin/test.cgi: #!/usr/bin/sh # Without these 2 lines, I get an Internal Server Error echo "Content-type: text/html" echo "" exec "/path/to/php-cgi" 'foo.php'; /bin/foo.php: <?php echo "this is foo.php!"; Output of http://mysite.com/bin/test.cgi: X-Powered-By: PHP/5.2.11 Content-type: text/html echo "Content-type: text/html" echo "" exec "/path/to//php-cgi" 'foo.php'; Output of http:/ /mysite.com/anypage.php: X-Powered-By: PHP/5.2.11 Content-type: text/html echo "Content-type: text/html" echo "" exec "/path/to//php-cgi" 'foo.php'; The things I note are: PHP is being executed, as noted by the X-Powered-By ... header. The source of /bin/test.cgi is output in the results. No matter what I put as the second argument of exec, it isn't passed to the php binary. I've tried '-i' to get phpinfo, '-v' to get the version... When I execute test.cgi via the shell, I get the expected results (the argument is passed to php, and it is reflected in the output). Any ideas about how to get this to work? UPDATE It appears that the reason the source of the test.cgi was appearing was due to errors. Anytime fatal error occurred, either within the cgi itself or with the command being executed by exec, it would cause the source of the cgi to appear. Within test.cgi, I can get the proper output with exec "/path/to/php-cgi" -h (I get the same thing as I would from CLI).

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• How to represent different entities that have identical behavior?

  - by Dominik

  I have several different entities in my domain model (animal species, let's say), which have a few properties each. The entities are readonly (they do not change state during the application lifetime) and they have identical behavior (the differ only by the values of properties). How to implement such entities in code? Unsuccessful attempts: Enums I tried an enum like this: enum Animals { Frog, Duck, Otter, Fish } And other pieces of code would switch on the enum. However, this leads to ugly switching code, scattering the logic around and problems with comboboxes. There's no pretty way to list all possible Animals. Serialization works great though. Subclasses I also thought about where each animal type is a subclass of a common base abstract class. The implementation of Swim() is the same for all Animals, though, so it makes little sense and serializability is a big issue now. Since we represent an animal type (species, if you will), there should be one instance of the subclass per application, which is hard and weird to maintain when we use serialization. public abstract class AnimalBase { string Name { get; set; } // user-readable double Weight { get; set; } Habitat Habitat { get; set; } public void Swim(); { /* swim implementation; the same for all animals but depends uses the value of Weight */ } } public class Otter: AnimalBase{ public Otter() { Name = "Otter"; Weight = 10; Habitat = "North America"; } } // ... and so on Just plain awful. Static fields This blog post gave me and idea for a solution where each option is a statically defined field inside the type, like this: public class Animal { public static readonly Animal Otter = new Animal { Name="Otter", Weight = 10, Habitat = "North America"} // the rest of the animals... public string Name { get; set; } // user-readable public double Weight { get; set; } public Habitat Habitat { get; set; } public void Swim(); } That would be great: you can use it like enums (AnimalType = Animal.Otter), you can easily add a static list of all defined animals, you have a sensible place where to implement Swim(). Immutability can be achieved by making property setters protected. There is a major problem, though: it breaks serializability. A serialized Animal would have to save all its properties and upon deserialization it would create a new instance of Animal, which is something I'd like to avoid. Is there an easy way to make the third attempt work? Any more suggestions for implementing such a model?

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• Structure of NAnt build scripts and solution structure on build server

  - by llykke

  We're in the process of streamlining/automating build, integration and unit testing as well as deployment. Our software is developed in Visual Studio where we have use both C# and VB.NET in our projects. A single project can be contained within multiple solutions (i.e. Utils project is used in both ProductA and ProductB solutions) For historical reasons our code repository isn't as well structured as one could have hoped for. E.g. Utils project might be located under ProductA solution (because that's were it was first used) but it was later deemed useful for productB development and merely just included into the solution of productB (but still located in a subdirectory of productA). I would like to use continous integration testing and have setup a CC.NET build server where I intend to use NAnt for creating the actual builds. Question 1: How should I structure my builds on the buildserver? Should I instruct CC.NET to retrieve all the projects for productB into a single library e.g. a file structure similar to -ProductB --Utils --BetterUtils --Data or should I opt for a filestructure similar to this -ProductA --Utils -ProductB --BetterUtils --Data and then just have the NAnt build scripts handle the references? Our references in VS doesn't match the actual location in the code repository so it's not possible today to just check-out productB solution and build it straight away (unfortunately). I hope this question makes sense? Question 2: Is it better to check out all the source code located in different projects into a single file folder (whilst retaining some kind of structure) and then build every thing at once or have multiple projects in CC.NET and then let the CC.NET server handle dependencies? Example: Should I have a seperate project in CC.NET for monitoring the automated build/test of Utils project when it's never released on it's own? Or should I just build/test it whilst building it as part of ProductB? I hope the above makes sense and that you can provide me with some arguments for using either option. We're nowhere near an ideal source code repository structure and I would prefer if I can resolve the lack of repository structure on the build server instead of having to clean up the structure of our repository. Switching away from VSS is (unfortunately) not an option. Right now our build consists of either deploying via VS clickonce or pressing F5 so just getting the build automated would be a huge step up for us. Thanks

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• Most efficient method to query a Young Tableau

  - by Matthieu M.

  A Young Tableau is a 2D matrix A of dimensions M*N such that: i,j in [0,M)x[0,N): for each p in (i,M), A[i,j] <= A[p,j] for each q in (j,N), A[i,j] <= A[i,q] That is, it's sorted row-wise and column-wise. Since it may contain less than M*N numbers, the bottom-right values might be represented either as missing or using (in algorithm theory) infinity to denote their absence. Now the (elementary) question: how to check if a given number is contained in the Young Tableau ? Well, it's trivial to produce an algorithm in O(M*N) time of course, but what's interesting is that it is very easy to provide an algorithm in O(M+N) time: Bottom-Left search: Let x be the number we look for, initialize i,j as M-1, 0 (bottom left corner) If x == A[i,j], return true If x < A[i,j], then if i is 0, return false else decrement i and go to 2. Else, if j is N-1, return false else increment j This algorithm does not make more than M+N moves. The correctness is left as an exercise. It is possible though to obtain a better asymptotic runtime. Pivot Search: Let x be the number we look for, initialize i,j as floor(M/2), floor(N/2) If x == A[i,j], return true If x < A[i,j], search (recursively) in A[0:i-1, 0:j-1], A[i:M-1, 0:j-1] and A[0:i-1, j:N-1] Else search (recursively) in A[i+1:M-1, 0:j], A[i+1:M-1, j+1:N-1] and A[0:i, j+1:N-1] This algorithm proceed by discarding one of the 4 quadrants at each iteration and running recursively on the 3 left (divide and conquer), the master theorem yields a complexity of O((N+M)**(log 3 / log 4)) which is better asymptotically. However, this is only a big-O estimation... So, here are the questions: Do you know (or can think of) an algorithm with a better asymptotical runtime ? Like introsort prove, sometimes it's worth switching algorithms depending on the input size or input topology... do you think it would be possible here ? For 2., I am notably thinking that for small size inputs, the bottom-left search should be faster because of its O(1) space requirement / lower constant term.

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• migrating an embedded jetty server from v6 to v7

  - by Ceilingfish

  Hi chaps, I have an embedded servlet which I use in unit tests, looks like this: public class UnitTestWebservices extends AbstractHandler { private Server server; private Map<Route,String> data = new HashMap<Route,String>(); public UnitTestWebservices(int port) throws Exception { server = new Server(port); server.setHandler(this); server.start(); } public void handle(String url, HttpServletRequest request, HttpServletResponse response, int arg3) throws IOException, ServletException { final Route route = Route.valueOf(request.getMethod(), url); final String content = data.get(route); if(content != null) { final ServletOutputStream stream = response.getOutputStream(); stream.print(content); stream.flush(); stream.close(); } else { response.sendError(HttpServletResponse.SC_NOT_FOUND); } } .... } That's written using version 6.1.24 of Jetty. I tried switching over to use Jetty 7.1.1.v20100517, and updated that code to this: public class UnitTestWebservices extends AbstractHandler { private Server server; private Map<Route,String> data = new HashMap<Route,String>(); public UnitTestWebservices(int port) throws Exception { server = new Server(port); server.setHandler(this); server.start(); } public void handle(String url, Request request, HttpServletRequest servletRequest, HttpServletResponse response) throws IOException, ServletException { final Route route = Route.valueOf(request.getMethod(), url); final String content = data.get(route); request.setHandled(true); response.setContentType("application/json"); if(content != null) { response.setStatus(HttpServletResponse.SC_OK); final Writer stream = response.getWriter(); stream.append(content); } else { response.sendError(HttpServletResponse.SC_NOT_FOUND); } } } But whenever I tried to access make a request to the server it would hang indefinitely. Has anyone experienced anything similar?. It also printed this into the log: log4j:WARN No appenders could be found for logger (org.eclipse.jetty.util.log). log4j:WARN Please initialize the log4j system properly. org.eclipse.jetty.server.Server@670655dd STOPPED +-UnitTestWebservices@50ef5502 started

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• crash in calloc

  - by mmd

  I'm trying to debug a program I wrote. I ran it inside gdb and I managed to catch a SIGABRT from inside calloc(). I'm completely confused about how this can arise. Can it be a bug in gcc or even libc?? More details: My program uses OpenMP. I ran it through valgrind in single-threaded mode with no errors. I also use mmap() to load a 40GB file, but I doubt that is relevant. Inside gdb, I'm running with 30 threads. Several identical runs (same input&CL) finished correctly, until the problematic one that I caught. On the surface this suggests there might be a race condition of some type. However, the SIGABRT comes from calloc() which is out of my control. Here is some relevant gdb output: (gdb) info threads [...] * 11 Thread 0x7ffff0056700 (LWP 73449) 0x00007ffff6a948a5 in raise () from /lib64/libc.so.6 [...] (gdb) thread 11 [Switching to thread 11 (Thread 0x7ffff0056700 (LWP 73449))]#0 0x00007ffff6a948a5 in raise () from /lib64/libc.so.6 (gdb) bt #0 0x00007ffff6a948a5 in raise () from /lib64/libc.so.6 #1 0x00007ffff6a96085 in abort () from /lib64/libc.so.6 #2 0x00007ffff6ad1fe7 in __libc_message () from /lib64/libc.so.6 #3 0x00007ffff6ad7916 in malloc_printerr () from /lib64/libc.so.6 #4 0x00007ffff6adb79f in _int_malloc () from /lib64/libc.so.6 #5 0x00007ffff6adbdd6 in calloc () from /lib64/libc.so.6 #6 0x000000000040e87f in my_calloc (re=0x7fff2867ef10, st=0, options=0x632020) at gmapper/../gmapper/../common/my-alloc.h:286 #7 read_get_hit_list_per_strand (re=0x7fff2867ef10, st=0, options=0x632020) at gmapper/mapping.c:1046 #8 0x000000000041308a in read_get_hit_list (re=<value optimized out>, options=0x632010, n_options=1) at gmapper/mapping.c:1239 #9 handle_read (re=<value optimized out>, options=0x632010, n_options=1) at gmapper/mapping.c:1806 #10 0x0000000000404f35 in launch_scan_threads (.omp_data_i=<value optimized out>) at gmapper/gmapper.c:557 #11 0x00007ffff7230502 in ?? () from /usr/lib64/libgomp.so.1 #12 0x00007ffff6dfc851 in start_thread () from /lib64/libpthread.so.0 #13 0x00007ffff6b4a11d in clone () from /lib64/libc.so.6 (gdb) f 6 #6 0x000000000040e87f in my_calloc (re=0x7fff2867ef10, st=0, options=0x632020) at gmapper/../gmapper/../common/my-alloc.h:286 286 res = calloc(size, 1); (gdb) p size $2 = 814080 (gdb) The function my_calloc() is just a wrapper, but the problem is not in there, as the real calloc() call looks legit. These are the limits set in the shell: $ ulimit -a core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited scheduling priority (-e) 0 file size (blocks, -f) unlimited pending signals (-i) 2067285 max locked memory (kbytes, -l) 64 max memory size (kbytes, -m) unlimited open files (-n) 1024 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 real-time priority (-r) 0 stack size (kbytes, -s) 10240 cpu time (seconds, -t) unlimited max user processes (-u) 1024 virtual memory (kbytes, -v) unlimited file locks (-x) unlimited The program is not out of memory, it's using 41GB on a machine with 256GB available: $ top -b -n 1 | grep gmapper 73437 user 20 0 41.5g 16g 15g T 0.0 6.6 55:17.24 gmapper-ls $ free -m total used free shared buffers cached Mem: 258437 195567 62869 0 82 189677 -/+ buffers/cache: 5807 252629 Swap: 0 0 0 I compiled using gcc (GCC) 4.4.6 20120305 (Red Hat 4.4.6-4), with flags -g -O2 -DNDEBUG -mmmx -msse -msse2 -fopenmp -Wall -Wno-deprecated -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS.

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• iPhone: value of selectedIndex for tab should be consistent, but isn't

  - by Janine

  This should be so simple... but something screwy is happening. My setup looks like this: MainViewController Tab Bar Controller 4 tabs, each of which loads WebViewController My AppDelegate contains an ivar, tabBarController, which is connected to the tab bar controller (this was all set up in Interface Builder). The leftmost tab is marked "selected" in IB. Within the viewWillAppear method in WebViewController, I need to know which tab was just selected so I can load the correct URL. I do this by switching on appDelegate.tabBarController.selectedIndex. When the app first runs and the leftmost tab is selected, selectedIndex is a large garbage value. After that, I get values from 0 to 3, which is as it should be, but they are in random order. Not only that, but each tab I touch reports a different value each time. This app is extremely simple right now and I can't imagine what I could have done to make things go this wrong. Has anyone seen (and hopefully solved) this behavior? Update: we have a request for code. There's not much to see. The tab bar controller gets loaded in applicationDidFinishLaunching: [self.mainViewController view]; //force nib to load [self.window addSubview:self.mainViewController.tabBarController.view] There is currently no code whatsoever in MainViewController.m other than the synthesize and release for tabBarController. From WebVewController.m: - (void)viewWillAppear:(BOOL)_animation { [super viewWillAppear:_animation]; NSURL *url; switch([S_UIDelegate mainViewController].tabBarController.selectedIndex) { case 0: url = [NSURL URLWithString:@"http://www.cnn.com"]; break; case 1: url = [NSURL URLWithString:@"http://www.facebook.com"]; break; case 2: url = [NSURL URLWithString:@"http://www.twitter.com"]; break; case 3: url = [NSURL URLWithString:@"http://www.google.com"]; break; default: url = [NSURL URLWithString:@"http://www.msnbc.com"]; } NSURLRequest *request = [NSURLRequest requestWithURL:url]; [webView loadRequest:request]; } This is where I'm seeing the random values.

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• compiling opencv 2.4 on a 64 bit mac in Xcode

  - by Walt

  I have an opencv project that I've been developing under ubuntu 12.04, on a parellels VM on a mac which has an x86_64 architecture. There have been many screen switching performance issues that I believe are due to the VM, where linux video modes flip around for a couple seconds while camera access is made by the opencv application. I decided to moved the project into Xcode on the mac side of the computer to continue the opencv development. However, I'm not that familiar with xcode and am having trouble getting the project to build correctly there. I have xcode installed. I downloaded and decompressed the latest version of opencv on the mac, and ran: ~/src/opencv/build/cmake-gui -G Xcode .. per the instructions from willowgarage and various other locations. This appeared to work fine (however I'm wondering now if I'm missing an architecture setting in here, although it is 64-bit intel in Xcode). I then setup an xcode project with the source files from the linux project and changed the include directories to use /opt/local/include/... rather than the /usr/local/include/... I switched xcode to use the LLVM GCC compiler in the build settings for the project then set the Apple LLVM Dialog for C++ to Language Dialect to GNU++11 (which seems possibly inconsistant with the line above) I'm not using a makefile in xcode, (that I'm aware of - it has its own project file...) I was also running into a linker issue that looked like they may be resolved with the addition of this linker flag: -lopencv_video based on a similar posting here: other thread however in that case the person was using a Makefile in their project. I've tried adding this linker flag under "Other Linker Flags" in xcode build settings but still get build errors. I think I may have two issues here, one with the architecture settings when building the opencv libraries with Cmake, and one with the linker flag settings in my project. Currently the build error list looks like this: Undefined symbols for architecture x86_64: "cv::_InputArray::_InputArray(cv::Mat const&)", referenced from: _main in main.o "cv::_OutputArray::_OutputArray(cv::Mat&)", referenced from: _main in main.o "cv::Mat::deallocate()", referenced from: cv::Mat::release() in main.o "cv::Mat::copySize(cv::Mat const&)", referenced from: cv::Mat::Mat(cv::Mat const&)in main.o cv::Mat::operator=(cv::Mat const&)in main.o "cv::Mat::Mat(_IplImage const*, bool)", referenced from: _main in main.o "cv::imread(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, int)", referenced from: _main in main.o ---SNIP--- ld: symbol(s) not found for architecture x86_64 collect2: ld returned 1 exit status Can anyone provide some guidance on what to try next? Thanks, Walt

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• PERL newbie : get a proper minimal debug_mode solution

  - by Michael Mao

  Hi all: I am learning PERL in a "head-first" manner. I am absolutely a newbie in this language: I am trying to have a debug_mode switch from CLI which can be used to control how my script works, by switching certain subroutines "on and off". And below is what I've got so far: #!/usr/bin/perl -s -w # purpose : make subroutine execution optional, # which is depending on a CLI switch flag use strict; use warnings; use constant DEBUG_VERBOSE => "v"; use constant DEBUG_SUPPRESS_ERROR_MSGS => "s"; use constant DEBUG_IGNORE_VALIDATION => "i"; use constant DEBUG_SETPPING_COMPUTATION => "c"; our ($debug_mode); mainMethod(); sub mainMethod # () { if(!$debug_mode) { print "debug_mode is OFF\n"; } elsif($debug_mode) { print "debug_mode is ON\n"; } else { print "OMG!\n"; exit -1; } checkArgv(); printErrorMsg("Error_Code_123", "Parsing Error at..."); verbose(); } sub checkArgv #() { print ("Number of ARGV : ".(1 + $#ARGV)."\n"); } sub printErrorMsg # ($error_code, $error_msg, ..) { if(defined($debug_mode) && !($debug_mode =~ DEBUG_SUPPRESS_ERROR_MSGS)) { print "You can only see me if -debug_mode is NOT set". " to DEBUG_SUPPRESS_ERROR_MSGS\n"; die("terminated prematurely...\n") and exit -1; } } sub verbose # () { if(defined($debug_mode) && ($debug_mode =~ DEBUG_VERBOSE)) { print "Blah blah blah...\n"; } } So far as I can tell, at least it works...: the -debug_mode switch doesn't interfere with normal ARGV the following commandlines work: ./optional.pl ./optional.pl -debug_mode ./optional.pl -debug_mode=v ./optional.pl -debug_mode=s However, I am puzzled when multiple debug_modes are "mixed", such as: ./optional.pl -debug_mode=sv ./optional.pl -debug_mode=vs I don't understand why the above lines of code "magically works". I see both of the "DEBUG_VERBOS" and "DEBUG_SUPPRESS_ERROR_MSGS" apply to the script, which is fine in this case. However, if there are some "conflicting" debug modes, I am not sure how to set the "precedence of debue_modes"? Also, I am not certain if my approach is good enough to Perlists and I hope I am getting my feet in the right direction. One biggest problem is that I now put if statements inside most of my subroutines for controlling their behavior under different modes. Is this okay? Is there a more elegant way? I know there must be a debug module from CPAN or elsewhere, but I wanna a real minimal solution that doesn't depend on any other module than the "default" And I cannot have any control on the environment where this script will be executed... Many thanks to the suggestions in advance.

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• Scala actors: receive vs react

  - by jqno

  Let me first say that I have quite a lot of Java experience, but have only recently become interested in functional languages. Recently I've started looking at Scala, which seems like a very nice language. However, I've been reading about Scala's Actor framework in Programming in Scala, and there's one thing I don't understand. In chapter 30.4 it says that using react instead of receive makes it possible to re-use threads, which is good for performance, since threads are expensive in the JVM. Does this mean that, as long as I remember to call react instead of receive, I can start as many Actors as I like? Before discovering Scala, I've been playing with Erlang, and the author of Programming Erlang boasts about spawning over 200,000 processes without breaking a sweat. I'd hate to do that with Java threads. What kind of limits am I looking at in Scala as compared to Erlang (and Java)? Also, how does this thread re-use work in Scala? Let's assume, for simplicity, that I have only one thread. Will all the actors that I start run sequentially in this thread, or will some sort of task-switching take place? For example, if I start two actors that ping-pong messages to each other, will I risk deadlock if they're started in the same thread? According to Programming in Scala, writing actors to use react is more difficult than with receive. This sounds plausible, since react doesn't return. However, the book goes on to show how you can put a react inside a loop using Actor.loop. As a result, you get loop { react { ... } } which, to me, seems pretty similar to while (true) { receive { ... } } which is used earlier in the book. Still, the book says that "in practice, programs will need at least a few receive's". So what am I missing here? What can receive do that react cannot, besides return? And why do I care? Finally, coming to the core of what I don't understand: the book keeps mentioning how using react makes it possible to discard the call stack to re-use the thread. How does that work? Why is it necessary to discard the call stack? And why can the call stack be discarded when a function terminates by throwing an exception (react), but not when it terminates by returning (receive)? I have the impression that Programming in Scala has been glossing over some of the key issues here, which is a shame, because otherwise it's a truly excellent book.

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• What are the benefits of using ORM over XML Serialization/Deserialization?

  - by Tequila Jinx

  I've been reading about NHibernate and Microsoft's Entity Framework to perform Object Relational Mapping against my data access layer. I'm interested in the benefits of having an established framework to perform ORM, but I'm curious as to the performance costs of using it against standard XML Serialization and Deserialization. Right now, I develop stored procedures in Oracle and SQL Server that use XML Types for either input or output parameters and return or shred XML depending on need. I use a custom database command object that uses generics to deserialize the XML results into a specified serializable class. By using a combination of generics, xml (de)serialization and Microsoft's DAAB, I've got a process that's fairly simple to develop against regardless of the data source. Moreover, since I exclusively use Stored Procedures to perform database operations, I'm mostly protected from changes in the data structure. Here's an over-simplified example of what I've been doing. static void main() { testXmlClass test = new test(1); test.Name = "Foo"; test.Save(); } // Example Serializable Class ------------------------------------------------ [XmlRootAttribute("test")] class testXmlClass() { [XmlElement(Name="id")] public int ID {set; get;} [XmlElement(Name="name")] public string Name {set; get;} //create an instance of the class loaded with data. public testXmlClass(int id) { GenericDBProvider db = new GenericDBProvider(); this = db.ExecuteSerializable("myGetByIDProcedure"); } //save the class to the database... public Save() { GenericDBProvider db = new GenericDBProvider(); db.AddInParameter("myInputParameter", DbType.XML, this); db.ExecuteSerializableNonQuery("mySaveProcedure"); } } // Database Handler ---------------------------------------------------------- class GenericDBProvider { public T ExecuteSerializable<T>(string commandText) where T : class { XmlSerializer xml = new XmlSerializer(typeof(T)); // connection and command code is assumed for the purposes of this example. // the final results basically just come down to... return xml.Deserialize(commandResults) as T; } public void ExecuteSerializableNonQuery(string commandText) { // once again, connection and command code is assumed... // basically, just execute the command along with the specified // parameters which have been serialized. } public void AddInParameter(string name, DbType type, object value) { StringWriter w = new StringWriter(); XmlSerializer x = new XmlSerializer(value.GetType()); //handle serialization for serializable classes. if (type == DbType.Xml && (value.GetType() != typeof(System.String))) { x.Serialize(w, value); w.Close(); // store serialized object in a DbParameterCollection accessible // to my other methods. } else { //handle all other parameter types } } } I'm starting a new project which will rely heavily on database operations. I'm very curious to know whether my current practices will be sustainable in a high-traffic situation and whether or not I should consider switching to NHibernate or Microsoft's Entity Framework to perform what essentially seems to boil down to the same thing I'm currently doing. I appreciate any advice you may have.

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• Arguments for moving from LINQtoSQL to Nhibernate?

  - by sah302

  Backstory: Hi all, I just spent a lot of time reading many of the LINQ vs Nhibernate threads here and on other sites. I work in a small development team of 4 people and we don't even have really any super experienced developers. We work for a small company that has a lot of technical needs but not enough developers to implement them (and hiring more is out of the question right now). Typically our projects (which individually are fairly small) have been coded separately and weren't really layered in anyway, code wasn't re-used, no class libraries, and we just use the LINQtoSQL .dbml files for our pojects, we really don't even use objects but pass around values and stuff, the only time we use objects is when inserting to a database (heck not even querying since you don't need to assign it to a type and can just bind to gridview). Despite all this as I said our company has a lot of technical needs, no one could come to us for a year and we would have plenty of work to implement requested features. Well I have decided to change that a bit first by creating class libraries and actually adding layers to our applications. I am trying to meet these guys halfway by still using LINQtoSQL as the ORM yet and still use VB as the language. However I am finding it a b***h of a time dealing with so many thing in LINQtoSQL that I found easy in Nhibernate (automatic handling of the session, criteria creation easier than expression trees, generic an dynamic querying easier etc.) So... Question: How can I convince my lead developers and other senior programmers that switching to Nhibernate is a good thing? That being in control of our domain objects is a good thing? That being able to implement interfaces is a good? I've tried exlpaining the advantages of this before but it's not understood by them because they've never programmed in a true OO & layered way. Also one of the counter arguments to this I can see is sqlMetal generates those classes automatically and therefore it saves a lot of time. I can't really counter that other than saying spending more time on infrastructure to make it more scalable and flexible is good, but they can't see how. Again, I know the features and advantages (somewhat enough I believe) of each, but I need arguments applicable to my context, hence why I provided the context. I just am not a very good arguer I guess. (Caveat: For all the LINQtoSQL lovers, I may just not be super proficient as LINQ, but I find it very cumbersome that you are required to download some extra library for dynamic queries which don't by default support guid comparisons, and I also find the way of updating entitites to be cumbersome as well in terms of data context managing, so it could just be that I suck hehe.)

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• Should we denormalize database to improve performance?

  - by Groo

  We have a requirement to store 500 measurements per second, coming from several devices. Each measurement consists of a timestamp, a quantity type, and several vector values. Right now there is 8 vector values per measurement, and we may consider this number to be constant for needs of our prototype project. We are using HNibernate. Tests are done in SQLite (disk file db, not in-memory), but production will probably be MsSQL. Our Measurement entity class is the one that holds a single measurement, and looks like this: public class Measurement { public virtual Guid Id { get; private set; } public virtual Device Device { get; private set; } public virtual Timestamp Timestamp { get; private set; } public virtual IList<VectorValue> Vectors { get; private set; } } Vector values are stored in a separate table, so that each of them references its parent measurement through a foreign key. We have done a couple of things to ensure that generated SQL is (reasonably) efficient: we are using Guid.Comb for generating IDs, we are flushing around 500 items in a single transaction, ADO.Net batch size is set to 100 (I think SQLIte does not support batch updates? But it might be useful later). The problem Right now we can insert 150-200 measurements per second (which is not fast enough, although this is SQLite we are talking about). Looking at the generated SQL, we can see that in a single transaction we insert (as expected): 1 timestamp 1 measurement 8 vector values which means that we are actually doing 10x more single table inserts: 1500-2000 per second. If we placed everything (all 8 vector values and the timestamp) into the measurement table (adding 9 dedicated columns), it seems that we could increase our insert speed up to 10 times. Switching to SQL server will improve performance, but we would like to know if there might be a way to avoid unnecessary performance costs related to the way database is organized right now. [Edit] With in-memory SQLite I get around 350 items/sec (3500 single table inserts), which I believe is about as good as it gets with NHibernate (taking this post for reference: http://ayende.com/Blog/archive/2009/08/22/nhibernate-perf-tricks.aspx). But I might as well switch to SQL server and stop assuming things, right? I will update my post as soon as I test it.

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• symfony/zend integration - blank screen

  - by user142176

  Hi, I need to use ZendAMF on a symfony project and I'm currently working on integrating the two. I have a frontend app with two modules, one of which is 'gateway' - the AMF gateway. In my frontend app config, I have the following in the configure function: // load symfony autoloading first parent::initialize(); // Integrate Zend Framework require_once('[MY PATH TO ZEND]\Loader.php'); spl_autoload_register(array('Zend_Loader', 'autoload')); The executeIndex function my the gateway actions.class.php looks like this // No Layout $this->setLayout(false); // Set MIME Type $this->getResponse()->setContentType('application/x-amf; charset='.sfConfig::get('sf_charset')); // Disable cause this is a non-html page sfConfig::set('sf_web_debug', false); // Create AMF Server $server = new Zend_Amf_Server(); $server->setClass('MYCLASS'); echo $server->handle(); return sfView::NONE; Now when I try to visit the url for the gateway module, or even the other module which was working perfectly fine until this attempt, I only see a blank screen, with not even the symfony dev bar loaded. Oddly enough, my symfony logs are not being updated as well, which suggests that Synfony is not even being 'reached'. So presumably the error has something to do with Zend, but I have no idea how to figure out what the error could be. One thing I do know for sure is that this is not a file path error, because if I change the path in the following line (a part of frontendConfiguration as shown above), I get a Zend_Amf_Server not found error. So the path must be correct. Also if I comment out this very same line, the second module resumes to normality, and my gateway broadcasts a blank x-amf stream. spl_autoload_register(array('Zend_Loader', 'autoload')); Does anyone have any tips on how I could attach this problem? Thanks P.S. I'm currently running an older version of Zend, which is why I am using Zend_Loader instead of Zend_autoLoader (I think). But I've tried switching to the new lib, but the error still remains. So it's not a version problem as well.

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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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• PInvokeStackImbalance C# call to unmanaged C++ function

  - by user287498

  After switching to VS2010, the managed debug assistant is displaying an error about an unbalanced stack from a call to an unmanaged C++ function from a C# application. The usuals suspects don't seem to be causing the issue. Is there something else I should check? The VS2008 built C++ dll and C# application never had a problem, no weird or mysterious bugs - yeah, I know that doesn't mean much. Here are the things that were checked: The dll name is correct. The entry point name is correct and has been verified with depends.exe - the code has to use the mangled name and it does. The calling convention is correct. The sizes and types all seem to be correct. The character set is correct. There doesn't seem to be any issues after ignoring the error and there isn't an issue when running outside the debugger. C#: [DllImport("Correct.dll", EntryPoint = "SuperSpecialOpenFileFunc", CallingConvention = CallingConvention.StdCall, CharSet = CharSet.Ansi, ExactSpelling = true)] public static extern short SuperSpecialOpenFileFunc(ref SuperSpecialStruct stuff); [StructLayout(LayoutKind.Sequential, Pack = 1, CharSet = CharSet.Ansi)] public struct SuperSpecialStruct { public int field1; [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)] public string field2; [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 20)] public string field3; [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 10)] public string field4; public ushort field5; public ushort field6; public ushort field7; public short field8; public short field9; public uint field10; public short field11; }; C++: short SuperSpecialOpenFileFunc(SuperSpecialStruct * stuff); struct SuperSpecialStruct { int field1; char field2[256]; char field3[20]; char field4[10]; unsigned short field5; unsigned short field6; unsigned short field7; short field8; short field9; unsigned int field10; short field11; }; Here is the error: Managed Debugging Assistant 'PInvokeStackImbalance' has detected a problem in 'Managed application path'. Additional Information: A call to PInvoke function 'SuperSpecialOpenFileFunc' has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature. Check that the calling convention and parameters of the PInvoke signature match the target unmanaged signature.

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• Phonegap web view thinks device screen taller than it is - results in offscreen tabbar

  - by Stin

  I have a jQTouch application loaded via server, so all I need to do is display the webpage full screen in PhoneGap for a faux-Native app. Unfortunatley each solution I've tried in PhoneGap has an issue: it thinks the screen size is taller than it is. This resuls in the tabbar that is pinned to the bottom being permantly offscreen and there fore unusable. You should be able to recreate this with my code below and going to the iTabbar online demo. Any thoughts on how to correct this issue? For background, going to the app page in iOS safari works fine, as well as saving the page to the home screen. In both cases the webview stops at the bottom of the screen and the tabbar is therefore viewable. Also, I'm using build.phonegap.com to compile (I'm not compiling locally) I've tried two methods: load the childBrowser plugin and call up the page (with navbar hidden via options) set the following config.xml parameter to prevent phonegap from switching to Safari, and then just load the link (preferable as it's cleaner in my mind. I've pasted my index.html and config.xml below) Details on the config.xml paramater: Open all links in WebView stay-in-webview with values true or false example: <preference name="stay-in-webview" value="true" /> if set to true, all links (even with target set to blank) will open in the app's webview only use this preference if you want pages from your server to take over your entire app default is false (Source: https://build.phonegap.com/docs/config-xml) my index.html: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <meta http-equiv="Content-type" content="text/html;charset=utf-8"> <title>MyApp</title> <script src="phonegap.js"></script> </head> <body> <p><a href="http://www.itabbar.com/itabbar/demo.html#home">Launch iTabbar</a></p> </body> </html> my config.xml: <?xml version="1.0" encoding="UTF-8" ?> <widget xmlns = "http://www.w3.org/ns/widgets" xmlns:gap = "http://phonegap.com/ns/1.0" id = "com.phonegap.myapp" versionCode="10" version = "1.0.0"> <!-- versionCode is optional and Android only --> <name>MyApp</name> <description> My app is... </description> <author href="https://myurl.com" email="[email protected]"> me </author> <preference name="stay-in-webview" value="true" /> </widget>

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• Separate specific #ifdef branches

  - by detly

  In short: I want to generate two different source trees from the current one, based only on one preprocessor macro being defined and another being undefined, with no other changes to the source. If you are interested, here is my story... In the beginning, my code was clean. Then we made a new product, and yea, it was better. But the code saw only the same peripheral devices, so we could keep the same code. Well, almost. There was one little condition that needed to be changed, so I added: #if defined(PRODUCT_A) condition = checkCat(); #elif defined(PRODUCT_B) condition = checkCat() && checkHat(); #endif ...to one and only one source file. In the general all-source-files-include-this header file, I had: #if !(defined(PRODUCT_A)||defined(PRODUCT_B)) #error "Don't make me replace you with a small shell script. RTFM." #endif ...so that people couldn't compile it unless they explicitly defined a product type. All was well. Oh... except that modifications were made, components changed, and since the new hardware worked better we could significantly re-write the control systems. Now when I look upon the face of the code, there are more than 60 separate areas delineated by either: #ifdef PRODUCT_A ... #else ... #endif ...or the same, but for PRODUCT_B. Or even: #if defined(PRODUCT_A) ... #elif defined(PRODUCT_B) ... #endif And of course, sometimes sanity took a longer holiday and: #ifdef PRODUCT_A ... #endif #ifdef PRODUCT_B ... #endif These conditions wrap anywhere from one to two hundred lines (you'd think that the last one could be done by switching header files, but the function names need to be the same). This is insane. I would be better off maintaining two separate product-based branches in the source repo and porting any common changes. I realise this now. Is there something that can generate the two different source trees I need, based only on PRODUCT_A being defined and PRODUCT_B being undefined (and vice-versa), without touching anything else (ie. no header inclusion, no macro expansion, etc)?

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• What would you suggest as a high school first language?

  - by ldigas

  Edit by OA: After reading some answers I'll just update the question a little. At first I put it a little bluntly, but some of those gave me some good arguments which have to be taken into consideration while making a stand on this one. (these are mostly picked up from comments and answers below). A few things to take into account: to many pupils this is a first programming language - at this stage most of them have trouble grasping a difference between data types, variable passing, ... and whatnot, less alone pointers and similar 'low level stuff' :) they will all have to pass this to get into next grade (well, big majority of them anyway) not all of them have computers at home, not all of them are willing to learn this, less alone interested in - so the concepts have to be taught on a finite time scale in school hours (as well as practice on computers) free literature is a bonus - the teacher will make some scripts and handaways, but still ... I wouldn't like to bear the parents with the burden of buying expensive literature (also, english is not a native language here ... and although they are all learning it, their ability to read it fluently is somewhat questionable) somebody gave an argument - "a language which does not get in the way of ideas" - good one accessibility on different platforms in not expecially important at this point - although most of the suggested ones are available on win as well as linux - not many macs in this part of europe (their prices are sky high for anything but specialised usage) I will check what are the licencing issues on ms express editions about using it massively in high schools for purposes like this - if someone has any info about this, please, do not be shy with it :) A friend of mine, informatics teacher - in EU it comes as something as junior cs teacher, in a local high school asked me what I thought about what should be the first language pupils should be taught? It is a technical school (a little more oriented towards mathematics than the gymnasium, but not computer oriented totally). So I'm asking you - what do you think should be the first language pupils are exposed to in highschool? They have been teaching Pascal so far, but she's not sure that's a good course. She thought about switching to C (which I resented; considering not all pupils have interests in programming, to start with, and should be taught something higher level since they are just gripping the idea of a loop and such ... for a start), I suggested python or ruby (preferably py since it handles all paradigms). What is your opinion on this one? I looked, but didn't find a similar question on SO, so if there is one, please just point me towards it. Edit: The assumption is that none of the pupils have been exposed to any programming in junior school. See also: What is the best way to teach young kids some basic programming concepts? Best ways to teach a beginner to program How and when do you teach a kid to code What is the easiest language to start with? High School Programming

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• What is causing this SQL 2005 Primary Key Deadlock between two real-time bulk upserts?

  - by skimania

  Here's the scenario: I've got a table called MarketDataCurrent (MDC) that has live updating stock prices. I've got one process called 'LiveFeed' which reads prices streaming from the wire, queues up inserts, and uses a 'bulk upload to temp table then insert/update to MDC table.' (BulkUpsert) I've got another process which then reads this data, computes other data, and then saves the results back into the same table, using a similar BulkUpsert stored proc. Thirdly, there are a multitude of users running a C# Gui polling the MDC table and reading updates from it. Now, during the day when the data is changing rapidly, things run pretty smoothly, but then, after market hours, we've recently started seeing an increasing number of Deadlock exceptions coming out of the database, nowadays we see 10-20 a day. The imporant thing to note here is that these happen when the values are NOT changing. Here's all the relevant info: Table Def: CREATE TABLE [dbo].[MarketDataCurrent]( [MDID] [int] NOT NULL, [LastUpdate] [datetime] NOT NULL, [Value] [float] NOT NULL, [Source] [varchar](20) NULL, CONSTRAINT [PK_MarketDataCurrent] PRIMARY KEY CLUSTERED ( [MDID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] - stackoverflow wont let me post images until my reputation goes up to 10, so i'll add them as soon as you bump me up, hopefully as a result of this question. ![alt text][1] [1]: http://farm5.static.flickr.com/4049/4690759452_6b94ff7b34.jpg I've got a Sql Profiler Trace Running, catching the deadlocks, and here's what all the graphs look like. stackoverflow wont let me post images until my reputation goes up to 10, so i'll add them as soon as you bump me up, hopefully as a result of this question. ![alt text][2] [2]: http://farm5.static.flickr.com/4035/4690125231_78d84c9e15_b.jpg Process 258 is called the following 'BulkUpsert' stored proc, repeatedly, while 73 is calling the next one: ALTER proc [dbo].[MarketDataCurrent_BulkUpload] @updateTime datetime, @source varchar(10) as begin transaction update c with (rowlock) set LastUpdate = getdate(), Value = t.Value, Source = @source from MarketDataCurrent c INNER JOIN #MDTUP t ON c.MDID = t.mdid where c.lastUpdate < @updateTime and c.mdid not in (select mdid from MarketData where LiveFeedTicker is not null and PriceSource like 'LiveFeed.%') and c.value <> t.value insert into MarketDataCurrent with (rowlock) select MDID, getdate(), Value, @source from #MDTUP where mdid not in (select mdid from MarketDataCurrent with (nolock)) and mdid not in (select mdid from MarketData where LiveFeedTicker is not null and PriceSource like 'LiveFeed.%') commit And the other one: ALTER PROCEDURE [dbo].[MarketDataCurrent_LiveFeedUpload] AS begin transaction -- Update existing mdid UPDATE c WITH (ROWLOCK) SET LastUpdate = t.LastUpdate, Value = t.Value, Source = t.Source FROM MarketDataCurrent c INNER JOIN #TEMPTABLE2 t ON c.MDID = t.mdid; -- Insert new MDID INSERT INTO MarketDataCurrent with (ROWLOCK) SELECT * FROM #TEMPTABLE2 WHERE MDID NOT IN (SELECT MDID FROM MarketDataCurrent with (NOLOCK)) -- Clean up the temp table DELETE #TEMPTABLE2 commit To clarify, those Temp Tables are being created by the C# code on the same connection and are populated using the C# SqlBulkCopy class. To me it looks like it's deadlocking on the PK of the table, so I tried removing that PK and switching to a Unique Constraint instead but that increased the number of deadlocks 10-fold. I'm totally lost as to what to do about this situation and am open to just about any suggestion. HELP!!

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• Problem setting row backgrounds in Android Listview

  - by zchtodd

  I have an application in which I'd like one row at a time to have a certain color. This seems to work about 95% of the time, but sometimes instead of having just one row with this color, it will allow multiple rows to have the color. Specifically, a row is set to have the "special" color when it is tapped. In rare instances, the last row tapped will retain the color despite a call to setBackgroundColor attempting to make it otherwise. private OnItemClickListener mDirectoryListener = new OnItemClickListener(){ public void onItemClick(AdapterView parent, View view, int pos, long id){ if (stdir.getStationCount() == pos) { stdir.moreStations(); return; } if (playingView != null) playingView.setBackgroundColor(Color.DKGRAY); view.setBackgroundColor(Color.MAGENTA); playingView = view; playStation(pos); } }; I have confirmed with print statements that the code setting the row to gray is always called. Can anyone imagine a reason why this code might intermittently fail? If there is a pattern or condition that causes it, I can't tell. I thought it might have something to do with the activity lifecycle setting the "playingView" variable back to null, but I can't reliably reproduce the problem by switching activities or locking the phone. private class DirectoryAdapter extends ArrayAdapter { private ArrayList<Station> items; public DirectoryAdapter(Context c, int resLayoutId, ArrayList<Station> stations){ super(c, resLayoutId, stations); this.items = stations; } public int getCount(){ return items.size() + 1; } public View getView(int position, View convertView, ViewGroup parent){ View v = convertView; LayoutInflater vi = (LayoutInflater)getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE); if (position == this.items.size()) { v = vi.inflate(R.layout.morerow, null); return v; } Station station = this.items.get(position); v = vi.inflate(R.layout.songrow, null); if (station.playing) v.setBackgroundColor(Color.MAGENTA); else if (station.visited) v.setBackgroundColor(Color.DKGRAY); else v.setBackgroundColor(Color.BLACK); TextView title = (TextView)v.findViewById(R.id.title); title.setText(station.name); return v; } };

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• Log4j: Issues about the FallbackErrorHandler

  - by rdogpink

  I am working on a client-server-application and wanted to implement a flexible Loggingframework, so I chose log4j, which doesn´t really evolve anymore, but it is still handy framework. Because the Logging happens along the network, i wanted a solution for the case, that the network drive isn´t available, so the Logger has to change its destination file(s). Now I wanted to use the FallbackErrorHandler (configured with a XML-File) from the Log4j-library and the implementation worked: When my network drive isn´t available, it switches to a local Logfile, so no logging should be lost. But I headded two problems since yesterday and couldn´t figure or find out, how to solve it. No return to initial Logging Configuration: When the network drive is on again and the Logger could write to the old destinations, log4j still logs at the local drive and I can´t figure out, how to notify the original (primary) Logger to start again. I also tried to attach a second Appender to the ErrorHandler, which should mirror the failed primary Logger, that it tries to write on the network destination and when the network is on again, it logs in both files, on the local and on the network drive. But unfortunately it didn´t work out, I only got a failure message that the ErrorHandler-content doesn´t fit. log4j:WARN The content of element type "errorHandler" must match "(param*,root-ref?,logger-ref*,appender-ref?)". This is the responsible code. <appender name="TraceAppender" class="org.apache.log4j.DailyRollingFileAppender"> <!-- The second appender-ref "TestAppender" leads to the error. --> <errorHandler class="org.apache.log4j.varia.FallbackErrorHandler"> <logger-ref ref="com.idoh"/> <appender-ref ref="TraceFallbackAppender"/> <appender-ref ref="TestAppender"/> </errorHandler> <param name="datePattern" value=".yyyy-MM-dd" /> <param name="file" value="logs/Trace.txt" /> <layout class="org.apache.log4j.PatternLayout"> <param name="ConversionPattern" value="%-6r %d{HH:mm:ss,SSS} [%t] %-5p - %m%n"/> </layout> </appender> So, how could I trigger log4j to reset to initial configuration or hold a second appender parallel to the "Local-Logger". My Application should work by itself and shouldn´t have to be restarted often. First Error message is swallowed: I recognized, that the first message, which leads to the switching between the primary logger and the FallbackErrorHandler (for example a logging-request to a readonly-File), is swallowed, so neither the primary logger logs it (because it can´t) nor the backup-Logger knows what it missed. So anybody else ran in this problem and could solve it? Or has any suggestions?

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• BeanCreationException in Spring Framework .WAR deploy to Tomcat 6 on Ubuntu 9.10

  - by JediPotPie

  I am in the process of switching from a Windows box to Ubunutu and I want to run my own local instance of Tomcat 6. I have installed Tomcat 6 without any basic issues. When I try to deploy a .war file that I had running on the Tomcat 6 instance on my Windows box I am getting the following error.... Apr 26, 2010 3:30:27 PM org.apache.catalina.core.ApplicationContext log INFO: Initializing Spring root WebApplicationContext Apr 26, 2010 3:30:27 PM org.apache.catalina.core.StandardContext listenerStart SEVERE: Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener org.springframework.beans.factory.CannotLoadBeanClassException: Cannot find class [com.ameren.eam.ldap.LdapDAONovellImpl] for bean with name 'testNovellDao' defined in ServletContext resource [/WEB-INF/applicationContext.xml]; nested exception is java.lang.ClassNotFoundException: com.ameren.eam.ldap.LdapDAONovellImpl at org.springframework.beans.factory.support.AbstractBeanFactory.resolveBeanClass(AbstractBeanFactory.java:1173) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.predictBeanType(AbstractAutowireCapableBeanFactory.java:479) at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:787) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:393) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:736) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:369) at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:261) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:199) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:45) at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3934) at org.apache.catalina.core.StandardContext.start(StandardContext.java:4429) at org.apache.catalina.manager.ManagerServlet.start(ManagerServlet.java:1249) at org.apache.catalina.manager.HTMLManagerServlet.start(HTMLManagerServlet.java:612) at org.apache.catalina.manager.HTMLManagerServlet.doGet(HTMLManagerServlet.java:136) at javax.servlet.http.HttpServlet.service(HttpServlet.java:617) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:616) at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:269) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAsPrivileged(Subject.java:537) at org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:301) at org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:162) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:283) at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:56) at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:189) at java.security.AccessController.doPrivileged(Native Method) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:185) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:525) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454) at java.lang.Thread.run(Thread.java:636) Caused by: java.lang.ClassNotFoundException: com.ameren.eam.ldap.LdapDAONovellImpl at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1399) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1245) at org.springframework.util.ClassUtils.forName(ClassUtils.java:230) at org.springframework.beans.factory.support.AbstractBeanDefinition.resolveBeanClass(AbstractBeanDefinition.java:381) at org.springframework.beans.factory.support.AbstractBeanFactory.resolveBeanClass(AbstractBeanFactory.java:1170) ... 40 more The class that is not being found is located at /WEB-INF/classes/com/ameren/eam/ldap/LdapDAONovellImpl.class relative to /WEB-INF/applicationContext.xml. I cannot figure out why it cannot find the class? Any ideas would be great.

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• How to reliably categorize HTTP sessions in proxy to corresponding browser' windows/tabs user is viewing?

  - by Jehonathan

  I was using the Fiddler core .Net library as a local proxy to record the user activity in web. However I ended up with a problem which seems dirty to solve. I have a web browser say Google Chrome, and the user opened like 10 different tabs each with different web URLs. The problem is that the proxy records all the HTTP session initiated by each pages separately, causing me to figure out using my intelligence the tab which the corresponding HTTP session belonged to. I understand that this is because of the stateless nature of HTTP protocol. However I am just wondering is there an easy way to do this? I ended up with below c# code for that in Fiddler. Still its not a reliable solution due to the heuristics. This is a modification of the sample project bundled with Fiddler core for .NET 4. Basically what it does is filtering HTTP sessions initiated in last few seconds to find the first request or switching to another page made by the same tab in browser. It almost works, but not seems to be a universal solution. Fiddler.FiddlerApplication.AfterSessionComplete += delegate(Fiddler.Session oS) { //exclude other HTTP methods if (oS.oRequest.headers.HTTPMethod == "GET" || oS.oRequest.headers.HTTPMethod == "POST") //exclude other HTTP Status codes if (oS.oResponse.headers.HTTPResponseStatus == "200 OK" || oS.oResponse.headers.HTTPResponseStatus == "304 Not Modified") { //exclude other MIME responses (allow only text/html) var accept = oS.oRequest.headers.FindAll("Accept"); if (accept != null) { if(accept.Count>0) if (accept[0].Value.Contains("text/html")) { //exclude AJAX if (!oS.oRequest.headers.Exists("X-Requested-With")) { //find the referer for this request var referer = oS.oRequest.headers.FindAll("Referer"); //if no referer then assume this as a new request and display the same if(referer!=null) { //if no referer then assume this as a new request and display the same if (referer.Count > 0) { //lock the sessions Monitor.Enter(oAllSessions); //filter further using the response if (oS.oResponse.MIMEType == string.Empty || oS.oResponse.MIMEType == "text/html") //get all previous sessions with the same process ID this session request if(oAllSessions.FindAll(a=>a.LocalProcessID == oS.LocalProcessID) //get all previous sessions within last second (assuming the new tab opened initiated multiple sessions other than parent) .FindAll(z => (z.Timers.ClientBeginRequest > oS.Timers.ClientBeginRequest.AddSeconds(-1))) //get all previous sessions that belongs to the same port of the current session .FindAll(b=>b.port == oS.port ).FindAll(c=>c.clientIP ==oS.clientIP) //get all previus sessions with the same referrer URL of the current session .FindAll(y => referer[0].Value.Equals(y.fullUrl)) //get all previous sessions with the same host name of the current session .FindAll(m=>m.hostname==oS.hostname).Count==0 ) //if count ==0 that means this is the parent request Console.WriteLine(oS.fullUrl); //unlock sessions Monitor.Exit(oAllSessions); } else Console.WriteLine(oS.fullUrl); } else Console.WriteLine(oS.fullUrl); Console.WriteLine(); } } } } };

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