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  • Is a web-server (e.g servlets) a good solution for an IM server?

    - by John
    I'm looking at a new app, broadly speaking an IM application with a strong client-server model - all communications go through a server so they can be logged centrally. The server will be Java in some form, clients could at this point be anything from a .NET Desktop app to Flex/Silverlight, to a simple web-interface using JS/AJAX. I had anticipated doing the server using standard J2EE so I get a thread-safe, multi-user server for 'free'... to make things simple let's say using Servlets (but in practice SpringMVC would be likely). This all seemed very neat but I'm concerned if the stateless nature of Servlets is the best approach. If my memory of servlets (been a year or two) is right, each time a client sent a HTTP request, typically a new message entered by the user, the servlet could not assume it had the user/chat in memory and might have to get it from the DB... regardless it has to look it up. Then it either has to use some PUSH system to inform other members of the chat, or cache that there are new messages, for other clients who poll the server using AJAX or similar - and when they poll it again has to lookup the chat, including new messages, and send the new data. I'm wondering if a better system would be the server is running core Java, and implements a socket-based communication with clients. This allows much more immediate data transfer and is more flexible if say the IM client included some game you could play. But then you're writing a custom server and sockets don't sound very friendly to a browser-based client on current browsers. Am I missing some big piece of the puzzle here, it kind of feels like I am? Perhaps a better way to ask the question would simply be "if the client was browser-based using HTML/JS and had to run on IE7+,FF2+ (i.e no HTML5), how would you implement the server?" edit: if you are going to suggest using XMPP, I have been trying to get my head around this in another question, so please consider if that's a more appropriate place to discuss this specifically.

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  • Load Empty Database table

    - by john White
    I am using SQLexpress and VS2008. I have a DB with a table named "A", which has an IdentitySpecification column named ID. The ID is auto-incremented. Even if the row is deleted, the ID still increases. After several data manipulation, the current ID has reached 15, for example. When I run the application if there's at least 1 row: if I add a new row, the new ID is 16. Everything is fine. If the table is empty (no row): if I add a new row, the new ID is 0, which is an error (I think). And further data manipulation (eg. delete or update) will result in an unhandled exception. Has anyone encountered this? PS. In my table definition, the ID has been selected as follow: Identity Increment = 1; Identity Seed =1; The DB load code is: dataSet = gcnew DataSet(); dataAdapter->Fill(dataSet,"A"); dataTable=dataSet->Tables["A"]; dbConnection->Open(); The Update button method dataAdapter->Update(dataSet,"tblInFlow"); dataSet->AcceptChanges(); dataTable=dataSet->Tables["tblInFlow"]; dataGrid->DataSource=dataTable; If I press Update: if there's at least a row: the datagrid view updates and shows the table correctly. if there's nothing in the table (no data row), the Add method will add a new row, but from ID 0. If I close the program and restart it again: the ID would be 16, which is correct. This is the add method row=dataTable->NewRow(); row["column1"]="something"; dataTable->Rows->Add(row); dataAdapter->Update(dataSet,"A"); dataSet->AcceptChanges(); dataTable=dataSet->Tables["A"];

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  • Unsafe, super-fast cross-process memory buffer?

    - by John
    Cross-process memory buffers always have some overhead, and my understanding is this is quite high. But what if you're implementing a cross-process render-buffer, this isn't critically important in the same way as other data so are there techniques we can use to get 'raw' access to a chunk of memory from multiple processes, with no safety nets apart from it not crashing? Or do modern operating systems simply not work with unabstracted memory in a way to make this possible? I'm working in C++ but the question applies to Win XP/Vista/7, MacOSX 10.5+ (& Linux less importantly).

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  • VBA - Prevent Excel 2007 from showing a defined names message box?

    - by John M
    I am working on a Excel 2007 workbook that will contain a macro to save the current sheet (a template) as a PDF file (no problem) a Excel 97-2003 file (problem) When saving the Excel file a messagebox appears asking about "Defined names of formulas in this workbook may display different values when they are recalculated...Do you want Excel to recalculate all formulas when this workbook is opened?". The user can then select Yes/No and then the file will save. How do I disable the messagebox from appearing? The default answer would be 'No'. My code for saving: Sub saveAs_97_2003_Workbook(tempFilePath As String, tempFileName As String) Dim Destwb As Workbook Dim SaveFormat As Long 'Remember the users setting SaveFormat = Application.DefaultSaveFormat 'Set it to the 97-2003 file format Application.DefaultSaveFormat = 56 ActiveSheet.Copy Set Destwb = ActiveWorkbook Destwb.CheckCompatibility = False With Destwb .SaveAs tempFilePath & tempFileName & ".xls", FileFormat:=56 .Close SaveChanges:=False End With 'Set DefaultSaveFormat back to the users setting Application.DefaultSaveFormat = SaveFormat End Sub

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  • C# - Erase all property values from a class?

    - by John M
    In a C# Winforms (3.5) application I have added a class that contains many properties (get/set) used to stored values from a 12 form long process. After form 12 I would like wipe out all the property values in the storing class so that the next user won't accidentally record values when starting the process at form 1. Is it possible to erase/destroy/dispose of all property values in a class? My class looks like this: private static int battery; public int Battery { get { return storeInspectionValues.battery; } set { storeInspectionValues.battery = value; } }

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  • Bitmap manipulation as a referenced object

    - by John Maloney
    I am working with a Bitmap object that I add annotations or copyright material to the image and then return the modified bitmap. My problem is that the Bitmap won't hold the changes made to it as it moves along the chain. I am treating it as a reference type and would assume that as it gets passed to each class it would carry the changes made to it. I have verified that the code inside of the MarkImage() classes does function, but which ever one gets called last is the one that has changes. Public Shared Function GetImage(ByVal imageDef As IImageDefinition) As Bitmap Dim image As Bitmap = Drawing.Image.FromFile(imageDef.Path) If Not imageDef.Authorization.IsAllowed(AuthKeys.CanViewWithoutCopyright) Then image = New MarkCopyrightImage(image).MarkImage() End If If Not imageDef.Authorization.IsAllowed(AuthKeys.CanViewWithoutAnnotations) Then image = New MarkAnnotateImage(image).MarkImage() End If Return image End Function How do I write changes to a bitmap object and then pass that object to another class while maintaining the changes? Answers in C# or VB are fine? Thanks

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  • R: How to separate character output in a loop?

    - by John
    I'm blanking on the best way to paste a list of strings together to go into an SQL statement... I'm having trouble with the separator bar | printing at the beginning when I don't want it to: foo = "blah" paste_all_together = NULL for (n in 1:4) { paste_together = paste(foo ,sep = "") paste_all_together = paste(paste_all_together, paste_together, sep = "|") } > paste_all_together [1] "|blah|blah|blah|blah" I just want it to print out "blah|blah|blah|blah". Do I need a nested loop, or is there a better itterator in R for doing this? Or perhaps a better way to input SQL statements?

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  • how to use oracle package to get rid of Global Temp table

    - by john
    I have a sample query like below: INSERT INTO my_gtt_1 (fname, lname) (select fname, lname from users) In my effort to getting rid of temporary tables I created a package: create or replace package fname_lname AS Type fname_lname_rec_type is record ( fname varchar(10), lname varchar(10) ); fname_lname_rec fname_lname_rec_type Type fname_lname_tbl_type is table of fname_lname_rec_type; function fname_lname_func ( v_fnam in varchar2, v_lname in varchar2 )return fname_lname_tbl_type pipelined; being new to oracle...creating this package took a long time. but now I can not figure out how to get rid of the my_gtt_1 how can i say... INSERT INTO <newly created package> (select fnma, name from users)

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  • Why does C++ linking use virtually no CPU? (updated)

    - by John
    On a native C++ project, linking right now can take a minute or two, yet during this time CPU drops from 100% during compilation to virtually zero. Does this mean linking is primarily a disk activity? If so, is this the main area an SSD would make big changes? But, why aren't all my OBJ files (or as many as possible) kept in RAM after compilation to avoid this? With 4Gb of RAM I should be able to save a lot of disk access and make it CPU-bound again, no? update: so the obvious follow-up is, can VC++ compiler and linker talk together better to streamline things and keep OBJ files in memory, similar to how Delphi does?

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  • ASP .NET Dynamically adding EventHandlers to button on Page_Load. EventHandler's do not fire the fir

    - by John
    Background: I am customizing an existing ASP .NET / C# application. It has it's own little "framework" and conventions for developers to follow when extending/customizing its functionality. I am currently extending some of it's administrative functionality, to which the framework provides a contract to enforce implementation of the GetAdministrationInterface() method, which returns System.Web.UI.Control. This method is called during the Page_Load() method of the page hosting the GUI interface. Problem: I have three buttons in my GUI, each of which have been assigned an Event Handler. My administration GUI loads up perfectly fine, but clicking any of the buttons doesn't do what I expect them to do. However, when I click them a second time, the buttons work. I placed breakpoints at the the beginning of each event handler method and stepped through my code. On the first click, none of the event handlers are triggered. On the second click, they are triggered. Any ideas? Example of Button Definition Button btn = new Button(); btn.Text = "Click Me Locked Screen"; bth.Click += new EventHandler(Btn_Click); Example of Event Handler Method Definition void Btn_Click(object sender, EventArgs e) { // Do Something }

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  • c++: truth assignment warning with arguments?

    - by John
    I use the following to work with arguments in my programs, but it seems to just hand me a warning (just a warning): "warning: suggest parentheses around assignment used as truth value" The beginning of the code is as follows: enum{OPT_DISP_H = 0x2, OPT_DISP_W = 0x1}; int main(int argc, char *argv[]) { int opt = 0x00; char c; while((++argv)[0] && argv[0][0]=='-'){ while(c =* ++argv[0]) switch(c){ case 'h': opt |= OPT_DISP_H; break; //etc.. The while(c =* ++argv[0]) part being where the warning persists. The code works fine, but what does this warning mean opposed to what is used? I think the code is c = *++argv[0], using the pointer. So why does the single = work and what is really recommended to be used?

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  • Django Forms save_m2m

    - by John
    Hi I have a model which has 2 many to many fields in it. one is a standard m2m field which does not use any through tables whereas the other is a bit more complecated and has a through table. I am using the Django forms.modelform to display and save the forms. The code I have to save the form is if form.is_valid(): f = form.save(commit=False) f.modified_by = request.user f.save() form.save_m2m() When i try to save the form I get the following error: Cannot set values on a ManyToManyField which specifies an intermediary model. I know this is happening when I do the form.save_m2m() because of the through table. What I'd liek to do is tell Django to ignore the m2m field with the through table but still save the m2m field without the through table. I can then go on to manually save the data for the through table field. Thanks

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  • Core Data Errors vs Exceptions Part 3

    - by John Gallagher
    My question is similar to this one. Background I'm creating a large number of objects in a core data store using NSOperations to speed things up. I've followed all the Core Data multithreading rules - I've got a single persistent store coordinator and a managed object context per thread that on save is merging back to the main managed object context. The Problem When the number of threads running at once is more than 1, I get the exception logged on save of my core data store: NSExceptionHandler has recorded the following exception: NSInternalInconsistencyException -- optimistic locking failure What I've Tried My code that creates new entities is quite complex - it makes entities that have relationships with other entities that could be being created in a separate thread. If I replace my object creation routine with some very simple code just making non-related entries, everything works perfectly. Initially, as well as the exceptions, I was getting a save error saying core data couldn't save due to the merge failing. I read the docs and realised I needed a merge policy on the Managed Object Context I was saving to. I set this up and as this question states, the save error goes away, but the exception remains. My Question Do I need to worry about these exceptions? If I do need to get rid of the exceptions, any ideas on how I do it?

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  • Released object crashes app

    - by John Smith
    I am using objective-C++ (+Boost) for iPhone development. I am in a rather tight loop and need to allocate and release a certain object. The code is something like this. for (int i=0;i<100;i++) { opt = [[FObj alloc] init]; //do stuff with opt [opt release]; } The FObj object is something like @interface FObj MyCPPObj * cppobj; @end In the implementation of FObj there is a dealloc method: -(void) dealloc { delete cppobj; //previously allocated with 'new' [super dealloc]; } I am afraid that if i don't release then the 'MyCPPObj's will just pile up. But releasing makes the app crash after the first loop. What am I doing wrong? Or perhaps should I make cppobj and boost::shared_ptr? (do boost shared pointers automatically release their objects when an objective-C++ object is deleted?)

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  • Sys. engineer has decided to dynamically transform all XSLs into DLLs on website build process. DLL

    - by John Sullivan
    Hello, OS: Win XP. Here is my situation. I have a browser based application. It is "wrapped" in a Visual Basic application. Our "Systems Engineer Senior" has decided to spawn DLL files from all of our XSL pages (many of which have duplicate names) upon building a new instance of the website and have the active server pages (ASPX) use the DLL instead. This has created a "known issue" in which ~200 DLL naming conflicts occur and, thus, half of our application is broken. I think a solution to this problem is that, thankfully, we're generating the names of the DLLs and linking them up with our application dynamically. Therefore we can do something kludgy like generate a hash and append it to the end of the DLL file name when we build our website, then always reference the DLL that had some kind of random string / hash appended to its name. Aside from outright renaming the DLLs, is there another way to have multiple DLLs with the same name register for one application? I think the answer is "No, only between different applications using a special technique." Please confirm. Another question I have on my mind is whether this whole idea is a good practice -- converting our XSL pages (which we use in mass -- every time a response from our web app occurs) into DLL functions that call a "function" to do what the XSL page did via an active server page (ASPX), when we were before just sending an XML response to an XSL page via aspx.

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  • Converting c++ string to int

    - by skazhy
    Hi! I have the following data in a c++ string John Doe 01.01.1970 I need to extract the date and time from it into int variables. I tried it like this: int last_space = text_string.find_last_of(' '); int day = int(text_string.substr(last_space + 1, 2)); But I got invalid cast from type ‘std::basic_string’ to type ‘int’. When I extract the "John Doe" part in another string variable, all works fine. What's wrong? I am trying to compile it with g++ -Wall -Werror.

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  • Major inconsistencies in Zend Framework

    - by John Nall
    Okay first of all let me just say Zend Framework is the greatest tool I have ever used in 30+ years of programming (well, for web development, Qt wins the desktop market). However, through my use I have noticed some glaring and annoying inconsistencies. For instance, Zend_Form_Element's have a setAttrib() method. Now why the hell is this the only method in that API which is abbrev.? Why then am I using setRequired() instead of setReq()? I have more examples, I am extremely nerd raged about this. It is completely ruining what could have been God's gift to web development. FOR FUTURE REFERENCE NEVER ABBREV. THINGS WHEN MAKING AN API. also always filter data before storing it i m o Who do we talk to about this, where something will actually get done about it?

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  • Rails 3 MySQL 2 reports an error in what looks to be valid SQL syntax

    - by John Judd
    I am trying to use the following bit of code to help in seeding my database. I need to add data continually over development and do not want to have to completely reseed data every time I add something new to the seeds.rb file. So I added the following function to insert the data if it doesn't already exist. def AddSetting(group, name, value, desc) Admin::Setting.create({group: group, name: name, value: value, description: desc}) unless Admin::Setting.find_by_sql("SELECT * FROM admin_settings WHERE group = '#{group}' AND name = '#{name}';").exists? end AddSetting('google', 'analytics_id', '', 'The ID of your Google Analytics account.') AddSetting('general', 'page_title', '', '') AddSetting('general', 'tag_line', '', '') This function is included in the db/seeds.rb file. Is this the right way to do this? However I am getting the following error when I try to run it through rake. rake aborted! Mysql2::Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'group = 'google' AND name = 'analytics_id'' at line 1: SELECT * FROM admin_settings WHERE group = 'google' AND name = 'analytics_id'; Tasks: TOP => db:seed (See full trace by running task with --trace) Process finished with exit code 1 What is confusing me is that I am generating correct SQL as far as I can tell. In fact my code generates the SQL and I pass that to the find_by_sql function for the model, Rails itself can't be changing the SQL, or is it? SELECT * FROM admin_settings WHERE group = 'google' AND name = 'analytics_id'; I've written a lot of SQL over the years and I've looked through similar questions here. Maybe I've missed something, but I cannot see it.

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  • Overhead of calling tiny functions from a tight inner loop? [C++]

    - by John
    Say you see a loop like this one: for(int i=0; i<thing.getParent().getObjectModel().getElements(SOME_TYPE).count(); ++i) { thing.getData().insert( thing.GetData().Count(), thing.getParent().getObjectModel().getElements(SOME_TYPE)[i].getName() ); } if this was Java I'd probably not think twice. But in performance-critical sections of C++, it makes me want to tinker with it... however I don't know if the compiler is smart enough to make it futile. This is a made up example but all it's doing is inserting strings into a container. Please don't assume any of these are STL types, think in general terms about the following: Is having a messy condition in the for loop going to get evaluated each time, or only once? If those get methods are simply returning references to member variables on the objects, will they be inlined away? Would you expect custom [] operators to get optimized at all? In other words is it worth the time (in performance only, not readability) to convert it to something like: ElementContainer &source = thing.getParent().getObjectModel().getElements(SOME_TYPE); int num = source.count(); Store &destination = thing.getData(); for(int i=0;i<num;++i) { destination.insert(thing.GetData().Count(), source[i].getName(); } Remember, this is a tight loop, called millions of times a second. What I wonder is if all this will shave a couple of cycles per loop or something more substantial? Yes I know the quote about "premature optimisation". And I know that profiling is important. But this is a more general question about modern compilers, Visual Studio in particular.

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  • Reasons for sticking with TEXT, NTEXT and IMAGE instead of (N)VARCHAR(max) and VARBINARY(max)

    - by John Assymptoth
    TEXT, NTEXT and IMAGE have been deprecated a long time ago and will, eventually, be removed from SQL Server. However, they are not going to be discontinued right away, not even in the next version of SQL Server, so it's not convenient for my enterprise to transform thousands of columns right away, even if it is using SQL Server 2012. What arguments can I use to postpone this migration? I know there are some advantages in using the new types. But I'm strictly looking for reasons not to migrate my data that is already functioning pretty well in the old types.

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  • What's the most efficient way to repeatedly remove leading text using Vim?

    - by John Topley
    What's the most efficient way to remove the text 2010-04-07 14:25:50,773 DEBUG This is a debug log statement - from a log file like the extract below using Vim? 2010-04-07 14:25:50,772 DEBUG This is a debug log statement - 9,8 2010-04-07 14:25:50,772 DEBUG This is a debug log statement - 1,11 2010-04-07 14:25:50,772 DEBUG This is a debug log statement - 5,2 2010-04-07 14:25:50,772 DEBUG This is a debug log statement - 8,4 This is what the result should look like: 9,8 1,11 5,2 8,4 Note that on this occasion I'm using gVim on Windows, so please don't suggest any UNIX programs which may be better suited to the task—I have to do it using Vim.

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  • Does a Distributed Version Control System really have no centralised repository?

    - by John
    It might seem a silly question, but how do you get a working drectory set up without a server to check out from? And how does a business keep a safe backed up copy of the repo? I assume then there must be a central repo... but then how exactly is it 'distributed'? I always thought of a server-client (SVN) Vs peer-2-peer (GIT) distinction, but I don't believe that can be correct unless tools like GIT are dependent on torrent-style technology?

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  • Is OpenID too complicated?

    - by John Leidegren
    I'm beginning to seriously doubt the OpenID community despite that fact that it works. I'm in the process of currently evaluating OpenID as an authentication service for 'this' site and while the promises are great, I just can't get it to work. And I'm really lost. I ask of the SO community to help me out here. Give me answers and show me examples so I can leverage this in the way it was meant to be. My scenario is very typical. I want to authenticate users through a specific Google Apps domain. If you have access to this Google Apps domain, then you have access to my web application. Where I get lost, is all the prerequisites and dependencies involved. What is XRD? What is Yadis? Why do I need XRD and Yadis? What do I need to do to deploy OpenID authentication on my website? Also, this is really important to me. When I login to SO, I use my Google Account. When I click the login button I'm presented with this confirmation page. Where I'm granting SO the right to use my Google Account credentials. Somehow, Google knows that it's "Stackoverflow.com" that's asking me if it's okay to login. And I wish to know what manner of control I have over this little text. I intend to deploy OpenID on several different domains but I would prefer if they would all work without having to be individually configured with special parameters, such as secret API keys and what not. However, I don't know for sure if this is a prerequisite of OpenID, that or the Federated Login API that Google provides.

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  • visual studio qt5 plugins not working on release

    - by John Smith
    I'm got this project where i'm showing images with a qt5 interface, i'm simply setting the Pixmap of a label with the qimage pixmap The thing is, it's working on a debug build, but not on a release build and i dont understand why. I already got a folder in my .Exe folder named "plugins" and a subfolder in it named "imageformats", and in this folder the file named "qjpeg.dll" So i coming here to see if someone has an idea on why it doesn't work ? Thanks in advance !

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