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Is re-using a Command and Connection object in ado.net a legitimate way of reducing new object creat

- by Neil Trodden

The current way our application is written, involves creating a new connection and command object in every method that access our sqlite db. Considering we need it to run on a WM5 device, that is leading to hideous performance. Our plan is to use just one connection object per-thread but it's also occurred to us to use one global command object per-thread too. The benefit of this is it reduces the overhead on the garbage collector created by instantiating objects all over the place. I can't find any advice against doing this but wondered if anyone can answer definitively if this is a good or bad thing to do, and why?

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Sum in array with match value

- by user325504

Dear all, I would like to do a simple sum per salesid in php - mysql after cross calculation between date (2 table) to get the real time commission, all the value already come out correctly but I got problem with final sum per sales id. salesid-commission aa0001 - 1000 bb0001 - 500 aa0001 - 200 bb0001 - 50 I already try with few sample in this web but still cannot meet the correct result. I cannot do the sum in mysql because of some reason (need calculation with other table) the result will be: aa0001 - 1200 bb0001 - 550 I aprreciated for any help to complated the test. Thank you so much.

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How does CreateRemoteThread work behind the scenes?

- by workinprogress

What does CreateRemoteThread do to actually create the remote thread?

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Saving part of audio file (java)

- by m159701m

Hi evryone, While playing an audio file (.wav) I want , if I resort to ctrl+c , to stop the playback and save part of the audio file in a file called "file2.wav". Here's the thread I'd like to add to my code. Unfortunately it doesn't work at all. Thanks in advance class myThread extends Thread{ public void run(){ try { PipedOutputStream poStream = new PipedOutputStream(); PipedInputStream piStream = new PipedInputStream(); poStream.connect(piStream); File cutaudioFile = new File ("file2.wav"); AudioInputStream ais = new AudioInputStream(piStream, AudioFileFormat.Type.WAVE , cutaudioFile); poStream.write(ais,AudioFileFormat.Type.WAVE,cutaudioFile); }catch (Exception e){ e.printStackTrace(); } } // end run } // end myThread

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Custom SQL Server driver

- by hoodoos

I had a crazy thought about writing my own SQL Server driver to make it work something like non-blocking http client, so it won't be thread thirsty and could handle lots of db queries within one thread. I tried to look over google for some guidelines about implementing SQL Server client protocol, but found none really, where do those guys get information about it when they write own implementations for PHP or python? I need a really low level to be documented so I can implement all phases of working with a connection through sockets. And would be really nice to have a an example in c# language. :)

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Java: How to test methods that call System.exit()?

- by Chris Conway

I've got a few methods that should call System.exit() on certain inputs. Unfortunately, testing these cases causes JUnit to terminate! Putting the method calls in a new Thread doesn't seem to help, since System.exit() terminates the JVM, not just the current thread. Are there any common patterns for dealing with this? For example, can I subsitute a stub for System.exit()? [EDIT] The class in question is actually a command-line tool which I'm attempting to test inside JUnit. Maybe JUnit is simply not the right tool for the job? Suggestions for complementary regression testing tools are welcome (preferably something that integrates well with JUnit and EclEmma).

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AudioRecord doesn't work for Motorola Milestone

- by hcpl

I'm having this problem only on Motorola Milestone. Code: // init recorder recordInstance = new AudioRecord(MediaRecorder.AudioSource.MIC, 8000, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT, 8000); recordInstance.startRecording(); //more code here recordInstance.stop(); The errorinformation I have (can't find more for the moment since I don't have a milestone myself for debugging): Uncaught handler: thread main exiting due to uncaught exception java.lang.IllegalStateException: stop() called on an uninitialized AudioRecord. at android.media.AudioRecord.stop(AudioRecord.java:51 6) Apparantly I'm not the only one with this problem. Some very similar threads I found (without solution): http://groups.google.com/group/android-developers/browse_thread/thread/6dd24aeb484b2e40 http://androidcommunity.com/forums/f2/problem-using-audiorecord-in-motorola-milestone-30935/ http://community.developer.motorola.com/t5/Android-App-Development-for/Problem-using-AudioRecord-on-Milestone-device/m-p/3889 http://www.fring.com/forums/showthread.php?t=16194

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tomcat multithreading problem

- by jutky

Hi all I'm writing a java application that runs in Tomcat, on a multi-core hardware. The application executes an algorithm and returns the answer to the user. The problem is that even when I run two requests simultaneously, the tomcat process uses at most one CPU core. As far as I understand each request in Tomcat is executed in separate thread, and JVM should run each thread on separate CPU core. What could be the problem that bounds the JVM or Tomcat to use no more than one core? Thanks in advance.

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Javascript self contained sandbox events and client side stack

- by amnon

I'm in the process of moving a JSF heavy web application to a REST and mainly JS module application . I've watched "scalable javascript application architecture" by Nicholas Zakas on yui theater (excellent video) and implemented much of the talk with good success but i have some questions : I found the lecture a little confusing in regards to the relationship between modules and sandboxes , on one had to my understanding modules should not be effected by something happening outside of their sandbox and this is why they publish events via the sandbox (and not via the core as they do access the core for hiding base libary) but each module in the application gets a new sandbox ? , shouldn't the sandbox limit events to the modoules using it ? or should events be published cross page ? e.g. : if i have two editable tables but i want to contain each one in a different sandbox and it's events effect only the modules inside that sandbox something like messabe box per table which is a different module/widget how can i do that with sandbox per module , ofcourse i can prefix the events with the moduleid but that creates coupling that i want to avoid ... and i don't want to package modules toghter as one module per combination as i already have 6-7 modules ? while i can hide the base library for small things like id selector etc.. i would still like to use the base library for module dependencies and resource loading and use something like yui loader or dojo.require so in fact i'm hiding the base library but the modules themself are defined and loaded by the base library ... seems a little strange to me libraries don't return simple js objects but usualy wrap them e.g. : u can do something like $$('.classname').each(.. which cleans the code alot , it makes no sense to wrap the base and then in the module create a dependency for the base library by executing .each but not using those features makes a lot of code written which can be left out ... and implemnting that functionality is very bug prone does anyonen have any experience with building a front side stack of this order ? how easy is it to change a base library and/or have modules from different libraries , using yui datatable but doing form validation with dojo ... ? some what of a combination of 2+4 if u choose to do something like i said and load dojo form validation widgets for inputs via yui loader would that mean dojocore is a module and the form module is dependant on it ? Thanks .

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Postgres : Post statement (or insert) asynchronous, non-blocking processing.

- by Hassan Syed

I'm wondering if it is possible, that after a collection of rows is inserted, to initiate an operation that is executed asynchronously, is non-blocking, and doesn't need to inform the originator of the request - of the result. I am working with large amounts of events and I can guarantee that the post-insert logic will not fail -- I just want to have a single insert thread in my event-sources, and I want this thread to keep flying without blocking, and without being responsible for any post-delivery book-keeping. I can tell you that I would potentially have a 100 of these jobs executing concurrently and each job might operate on 5 tables with anywhere between 200-1000 inserts on each of these tables. A hint in the right direction should be enough.

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Registering a delegate function with an ISO C++ callback (on mono)

- by Stick it to THE MAN

I am thinking of wrapping ISO C++ code in C# class. The only problem so far is how to deal with the C++ callbacks. In .Net languages (C# and Vb.Net), I believe the callback equivalent. Sticking with C# for now, can anyone recommend a way that I can register the C# delegate functions with my ISO C++ code. The ISO C++ code is a notification library, and I want to be able to "push" the notifications to the mono framework (i.e. C# delegates in this case). My underlying assumption is that the mechanism/steps to implement this would be the same for the .Net languages - I'll just have to code the actual delegates in the .Net language of choice - is that assumption correct? Last but not the least, is the question of thread saftey. The underlying ISO C++ code that I am exposing to .Net (mono to be more specific), is both re-ntrant and thread safe - do I have to do anything "extra" to call .Net delegate from my ISO C++ code?

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jQuery Validation Plugin: Packer undefined error?

- by Rosarch

I'm using the jQuery validation plugin from bassistance.de. It works fine. From <head>: <script type="text/javascript" src="/static/JQuery.js"></script> <script type="text/javascript" src="/static/js-lib/jquery.validate.pack.js"></script> <script type="text/javascript" src="/static/js-lib/jquery.validate.additional-methods.js"></script> At first, this was the only validation code I had, and it worked: $("form").validate(); $("#form-username").rules("add", { required: true, email: true, }); It was validating this HTML: <form id="form-username-form" action="api/user_of_email" method="get"> <p> <label for="form-username">Email:</label> <input type="text" name="email" id="form-username" /> <input type="submit" value="Submit" id="form-submit" /> </p> </form> Great, everything works. But then I add this JS: $("#form-choose-options input[type='text']").rules("add", { number: true, }); to validate this markup: <form id="form-choose-options" action="api/set_options" method="get"> <p> <label for="form-min-credits">Min credits per term:</label><input type="text" name="min_credits" id="form-min-credits" /> <br /> <label for="form-optimal-credits">Optimal credits per term:</label><input type="text" name="optimal_credits" id="form-optimal-credits" /> <br /> <label for="form-max-credits">Max credits per term:</label><input type="text" name="max_credits" id="form-max-credits" /> <br /> <label for="form-low-GPA">Lowest acceptable GPA:</label><input type="text" name="low_GPA" id="form-low-GPA" /> <br /> <label for="form-high-GPA">Highest realistic GPA:</label><input type="text" name="high_GPA" id="form-high-GPA" /> <br /> <input type="hidden" class="user-pk" name="pk"/> <input type="submit" value="Submit" /> </p> </form> This causes a javascript error on document load: $.data(f.form, "validator") is undefined The error is from the packer function. What am I doing wrong?

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How to handle all unhandled exceptions when using Task Parallel Library?

- by Buu Nguyen

I'm using the TPL (Task Parallel Library) in .NET 4.0. I want to be able to centralize the handling logic of all unhandled exceptions by using the Thread.GetDomain().UnhandledException event. However, in my application, the event is never fired for threads started with TPL code, e.g. Task.Factory.StartNew(...). The event is indeed fired if I use something like new Thread(threadStart).Start(). This MSDN article suggests to use Task#Wait() to catch the AggregateException when working with TPL, but that is not I want because it is not "centralized" enough a mechanism. Does anyone experience same problem at all or is it just me? Do you have any solution for this?

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java socket programming problem

- by mk.persia

Hi, what's wrong with my code? sorry about my bad English package sockettest; import java.io.*; import java.net.*; class sevr implements Runnable{ public void run() { ServerSocket sSkt = null; Socket skt = null; BufferedReader br = null; BufferedWriter bw = null; try{ System.out.println("Server: is about to create socket"); sSkt = new ServerSocket(6666); System.out.println("Server: socket created"); } catch(IOException e){ System.out.println("Server: socket creation failure"); } try{ System.out.println("Server: is listening"); skt = sSkt.accept(); System.out.println("Server: Connection Established"); } catch(IOException e){ System.out.println("Server: listening failed"); } try{ System.out.println("Server: creating streams"); br = new BufferedReader(new InputStreamReader(skt.getInputStream())); bw = new BufferedWriter(new OutputStreamWriter(skt.getOutputStream())); System.out.println("Server: stream done"); } catch(IOException e){ System.out.println("Server: stream failed"); } System.out.println("Server: reading the request"); try{ String line = null; while((line =br.readLine()) != null){ System.out.println("Server: client said- "+ line); } } catch(IOException e){ System.out.println("Server: reading failed"); } System.out.println("Server: reading fished"); System.out.println("Server: responding"); try{ bw.write("Hi! I am server!"); } catch(IOException e){ System.out.println("Server: responding failed"); } System.out.println("Server: responding finished"); System.out.println("Server: is finishing"); try { br.close(); bw.close(); skt.close(); sSkt.close(); } catch (IOException e) { System.out.println("Server: finishing failed"); } System.out.println("Server: done"); } } class clnt implements Runnable{ public void run() { Socket skt = null; BufferedReader br = null; BufferedWriter bw = null; try{ System.out.println("Client: about to create socket"); skt = new Socket(InetAddress.getLocalHost(),6666); System.out.println("Client: socket created"); } catch(IOException e){ System.out.println("Client: socket creation failure"); } try{ System.out.println("Client: creating streams"); br = new BufferedReader(new InputStreamReader(skt.getInputStream())); bw = new BufferedWriter(new OutputStreamWriter(skt.getOutputStream())); System.out.println("Client: stream done"); } catch(IOException e){ System.out.println("Client: stream failed"); } System.out.println("Client: requesting"); try{ bw.write("Hi! I am Client!"); } catch(IOException e){ System.out.println("Client: requesting failed"); } System.out.println("Client: requesting finished"); System.out.println("Client: reading the respond"); try{ String line = null; while((line =br.readLine()) != null){ System.out.println("Client: server said- "+ line); } } catch(IOException e){ System.out.println("Client: reading failed"); } System.out.println("Client: reading fished"); System.out.println("Clientrver: is finishing"); try { br.close(); bw.close(); skt.close(); } catch (IOException e) { System.out.println("Client: finishing failed"); } System.out.println("Client: done"); } } public class Main { public static void main(String[] args) { System.out.println("Main started"); Thread sThread = new Thread(new sevr()); Thread cThread = new Thread(new clnt()); sThread.start(); cThread.start(); try { sThread.join(); cThread.join(); } catch (InterruptedException ex) { System.out.println("joining failed"); } System.out.println("Main done"); } } output: Main started Server: is about to create socket Client: about to create socket Client: socket created Client: creating streams Server: socket created Server: is listening Server: Connection Established Server: creating streams Server: stream done Server: reading the request Client: stream done Client: requesting Client: requesting finished Client: reading the respond and it waits here forever!

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Kohana v3, escape illegal characters?

- by Dom

Quick question, does Kohana (version 3) automatically escape data that is passed into ORM::factory..... (and everywhere else that has to do with the database)? For example: $thread = ORM::factory('thread', $this->request->param('id')); Would the data passed in the second argument be auto-escaped before it goes in the SQL query or do I have to manually do it? Probably a stupid question and it's better to be safe than sorry, but yeah... I usually do manually escape the data, but I want to know if Kohana does this for me? Thanks

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BizTalk Server Threading in Receive Pipelines

- by ToxicAvenger

I am building custom pipeline components for receive pipelines in BizTalk Server (2006 and 2009). I am building the components in a streaming fashion. My question: for any single inbound message, if I have a disassembling component, when I create n messages from a single inbound message, will the message agent always use a single thread when reading the (body) streams and persisting the messages to the message box? I would think so, but confirmation would be helpful. Say if I create five messages in the disassembler, will any of these messages be persisted sequentially from the same thread? Or could these messages be processed in parallel?

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environment configuration for tests running in NUnit

- by Frank Schwieterman

I have some integration tests that hit a webserver and verify certain functionalities. Depending on the build environment, the server will be at a different address (http://localhost:8080/, http://test-vm/, etc). I would like to run these tests from a TFS build. I'm wondering whats the appropriate way to configure these tests? Would I just add a setting to the config file? I'm doing that currently. Incidentally we do have a separate branch per test environment, so I could have a different config file checked in for each environment. I wonder if there is a better way though? I'd like the build project to be able to tell the test what server to test. This seems better because then I don't have to maintain config information on a per branch basis. I believe I'd be using NUnit for Team Build (http://nunit4teambuild.codeplex.com/) to get NUnit/TFS to play together.

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Odd optimization problem under MSVC

- by Goz

I've seen this blog: http://igoro.com/archive/gallery-of-processor-cache-effects/ The "weirdness" in part 7 is what caught my interest. My first thought was "Thats just C# being weird". Its not I wrote the following C++ code. volatile int* p = (volatile int*)_aligned_malloc( sizeof( int ) * 8, 64 ); memset( (void*)p, 0, sizeof( int ) * 8 ); double dStart = t.GetTime(); for (int i = 0; i < 200000000; i++) { //p[0]++;p[1]++;p[2]++;p[3]++; // Option 1 //p[0]++;p[2]++;p[4]++;p[6]++; // Option 2 p[0]++;p[2]++; // Option 3 } double dTime = t.GetTime() - dStart; The timing I get on my 2.4 Ghz Core 2 Quad go as follows: Option 1 = ~8 cycles per loop. Option 2 = ~4 cycles per loop. Option 3 = ~6 cycles per loop. Now This is confusing. My reasoning behind the difference comes down to the cache write latency (3 cycles) on my chip and an assumption that the cache has a 128-bit write port (This is pure guess work on my part). On that basis in Option 1: It will increment p[0] (1 cycle) then increment p[2] (1 cycle) then it has to wait 1 cycle (for cache) then p[1] (1 cycle) then wait 1 cycle (for cache) then p[3] (1 cycle). Finally 2 cycles for increment and jump (Though its usually implemented as decrement and jump). This gives a total of 8 cycles. In Option 2: It can increment p[0] and p[4] in one cycle then increment p[2] and p[6] in another cycle. Then 2 cycles for subtract and jump. No waits needed on cache. Total 4 cycles. In option 3: It can increment p[0] then has to wait 2 cycles then increment p[2] then subtract and jump. The problem is if you set case 3 to increment p[0] and p[4] it STILL takes 6 cycles (which kinda blows my 128-bit read/write port out of the water). So ... can anyone tell me what the hell is going on here? Why DOES case 3 take longer? Also I'd love to know what I've got wrong in my thinking above, as i obviously have something wrong! Any ideas would be much appreciated! :) It'd also be interesting to see how GCC or any other compiler copes with it as well! Edit: Jerry Coffin's idea gave me some thoughts. I've done some more tests (on a different machine so forgive the change in timings) with and without nops and with different counts of nops case 2 - 0.46 00401ABD jne (401AB0h) 0 nops - 0.68 00401AB7 jne (401AB0h) 1 nop - 0.61 00401AB8 jne (401AB0h) 2 nops - 0.636 00401AB9 jne (401AB0h) 3 nops - 0.632 00401ABA jne (401AB0h) 4 nops - 0.66 00401ABB jne (401AB0h) 5 nops - 0.52 00401ABC jne (401AB0h) 6 nops - 0.46 00401ABD jne (401AB0h) 7 nops - 0.46 00401ABE jne (401AB0h) 8 nops - 0.46 00401ABF jne (401AB0h) 9 nops - 0.55 00401AC0 jne (401AB0h) I've included the jump statetements so you can see that the source and destination are in one cache line. You can also see that we start to get a difference when we are 13 bytes or more apart. Until we hit 16 ... then it all goes wrong. So Jerry isn't right (though his suggestion DOES help a bit), however something IS going on. I'm more and more intrigued to try and figure out what it is now. It does appear to be more some sort of memory alignment oddity rather than some sort of instruction throughput oddity. Anyone want to explain this for an inquisitive mind? :D Edit 3: Interjay has a point on the unrolling that blows the previous edit out of the water. With an unrolled loop the performance does not improve. You need to add a nop in to make the gap between jump source and destination the same as for my good nop count above. Performance still sucks. Its interesting that I need 6 nops to improve performance though. I wonder how many nops the processor can issue per cycle? If its 3 then that account for the cache write latency ... But, if thats it, why is the latency occurring? Curiouser and curiouser ...

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Reducing a normalized table to one value

- by Dio

Hello, I'm sure this has been asked but I'm not quite sure how to properly search for this question, my apologies. I have two tables, Foo and Bar. For has one row per Food, bar has many rows per food matching descriptors. Foo name id Apple 1 Orange 2 Bar id description 1 Tasty 1 Ripe 2 Sweet etc (sorry for the somewhat contrived example). I'm trying to return a query where if, for each row in Foo, Bar contains a descriptor in ('Tasty', 'Juicy') return true ex: Output Apple True Orange False I had been solving this somewhat trivially with a case when I only had one item to match select Foo.name, case bar.description when 'Tasty' then True else 'False' end from Foo left join Bar on foo.id = bar.id where bar.description = 'Tasty' But with multiple items, I keep ending up with extra rows: Output Apple True Apple False etc etc Can someone point me in the right direction on how to think about this problem or what I should be doing? Thank you.

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Download data in background with iOS4

- by Sagar

As per the latest update of Kindle V2.5, it has support of "continue downloading books while the app is in the background on iOS 4 devices". How is it possible to download content in background? As per the iOS multitasking documentation, only audio, voip & location updates are possible in background. And I've also maken sure that NSURLConnection doesn't download new data work while app goes background. Then how's it possible with Kindle app? Edit: I haven't checked Kindle App in iOS4 multitasking enabled device. So if anyone let me (& community) know what exactly Kindle app does to download, that would be very much helpful.

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Frame skipping with OpenGL and WinAPI?

- by user146780

Here is my situation. I'm creating a drawing application using OpenGL and WinAPI. My OpenGL frame has scrollbars which renders the screen and modifies GlTranslatef when it gets a scroll message. The problem is wen I get too many shapes the scrollbar is less responsive since it cannot rerender it each and every time it gets a scroll message. How could I make it so the scrollbar has priority. I want it to skip drawing if it would compromise the smoothness of the scrolling. I thought of doing rendering on a separate thread but I was told all UI things should stay on the same thread. Thanks

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OpenGL Performance Questions

- by Daniel

This subject, as with any optimisation problem, gets hit on a lot, but I just couldn't find what I (think) I want. A lot of tutorials, and even SO questions have similar tips; generally covering: Use GL face culling (the OpenGL function, not the scene logic) Only send 1 matrix to the GPU (projectionModelView combination), therefore decreasing the MVP calculations from per vertex to once per model (as it should be). Use interleaved Vertices Minimize as many GL calls as possible, batch where appropriate And possibly a few/many others. I am (for curiosity reasons) rendering 28 million triangles in my application using several vertex buffers. I have tried all the above techniques (to the best of my knowledge), and received almost no performance change. Whilst I am receiving around 40FPS in my implementation, which is by no means problematic, I am still curious as to where these optimisation 'tips' actually come into use? My CPU is idling around 20-50% during rendering, therefore I assume I am GPU bound for increasing performance. Note: I am looking into gDEBugger at the moment Cross posted at Game Development

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Applet tag error

- by Yvan JANSSENS

Hi, I'm getting a FileNotFound error when I try to include my applet. It tries to include a .class file, while I provide a .jar file. Here's the java console output: at java.lang.Thread.run(Thread.java:637) Caused by: java.io.FileNotFoundException: /Users/yvanjanssens/NetBeansProjects/yBlackJack/yBlackJackApplet.class (No such file or directory) at java.io.FileInputStream.open(Native Method) at java.io.FileInputStream.<init>(FileInputStream.java:106) at java.io.FileInputStream.<init>(FileInputStream.java:66) And here's my Applet code: <applet code="yBlackJackApplet" archive="yBlackJack.jar" width="100%" height="100%" > </applet> Thanks! Yvan

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iPhone - how to be notified of call completion

- by ecodan

Hi- I'm developing an application that needs to take action on completed phone calls, preferably right after the call ends but minimally once per day. I've read up on the new CoreTelphony framework, and it seems I can get call events if my app is active, but I don't see how to launch/wake my app when a call ends if my app is not the foreground app. I also don't see how any of the new pseudo-background "modes" would allow my app to listen for these events in the background. Do any of you know how this might be done? If post-call processing isn't possible, then I'd like to figure out a way to automatically wake my app up once per day, pull all of the call events since the last wakeup, and process them. I know how I might do this with Push or Local notifications, but my understanding is that those require user action to continue; in this case, I just want the processing to happen automatically. Is there a mechanism that would enable this? Thanks, Dan

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In JSF, how to handle repeating over a list that mutates

- by Jon

Hello, In a JSF page, I am iterating over a list of items provided by a session-scoped backing bean. The list needs to be kept up-to-date, so it is replaced with a fresh list every X minutes by a thread (in a thread-safe way). On my page, for each item I provide some text inputs and an "Update" button. If the list is refreshed before I hit "Update", the update does not happen (which is my problem). I happen to be using a4j:repeat, but I think this could also apply to other methods of iteration, including using dataTables. Any thoughts on how I can do this in a non-hackish way? Thanks!

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