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  • Velocity framework servlet

    - by GustlyWind
    I have a module written in servlets and needs to be recently moved to velocity framework So in the process I am rewriting the web.xml to create velocity servlet object whcih calls our original servlet . Now if this has to be moved to <servlet> <servlet-name>VeloServlet</servlet-name> <servlet-class>org.apache.velocity.tools.view.servlet.VelocityViewServlet</servlet-class> </servlet> How can we acheive this and what are all changes need to use the existing servlet as it is. My Existing servlet looks like <servlet-name>DataBridgeServlet</servlet-name> <servlet-class>com.jda.pwm.databridge.framework.common.DataBridgeServlet</servlet-class> <init-param> <param-name>jda.databridge.config.path</param-name> <param-value>d:/usr/databridge/conf</param-value> </init-param> This is loaded using the url http://localhost:8080/databridge/databridgeservlet So in the newer case how velocity servlet calls this servlet

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  • Rendering Swing Components to an Offscreen buffer

    - by Nick C
    I have a Java (Swing) application, running on a 32-bit Windows 2008 Server, which needs to render it's output to an off-screen image (which is then picked up by another C++ application for rendering elsewhere). Most of the components render correctly, except in the odd case where a component which has just lost focus is occluded by another component, for example where there are two JComboBoxes close to each other, if the user interacts with the lower one, then clicks on the upper one so it's pull-down overlaps the other box. In this situation, the component which has lost focus is rendered after the one occluding it, and so appears on top in the output. It renders correctly in the normal Java display (running full-screen on the primary display), and attempting to change the layers of the components in question does not help. I am using a custom RepaintManager to paint the components to the offscreen image, and I assume the problem lies with the order in which addDirtyRegion() is called for each of the components in question, but I can't think of a good way of identifying when this particular state occurs in order to prevent it. Hacking it so that the object which has just lost focus is not repainted stops the problem, but obviously causes the bigger problem that it is not repainted in all other, normal, circumstances. Is there any way of programmatically identifying this state, or of reordering things so that it does not occur? Many thanks, Nick

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  • Python: Best way to check for Python version in program that uses new language features?

    - by Mark Harrison
    If I have a python script that requires at least a particular version of python, what is the correct way to fail gracefully when an earlier version of python is used to launch the script? How do I get control early enough to issue an error message and exit? For example, I have a program that uses the ternery operator (new in 2.5) and "with" blocks (new in 2.6). I wrote a simple little interpreter-version checker routine which is the first thing the script would call ... except it doesn't get that far. Instead, the script fails during python compilation, before my routines are even called. Thus the user of the script sees some very obscure synax error tracebacks - which pretty much require an expert to deduce that it is simply the case of running the wrong version of python. update I know how to check the version of python. The issue is that some syntax is illegal in older versions of python. Consider this program: import sys if sys.version_info < (2, 4): raise "must use python 2.5 or greater" else: # syntax error in 2.4, ok in 2.5 x = 1 if True else 2 print x When run under 2.4, I want this result $ ~/bin/python2.4 tern.py must use python2.5 or greater and not this result: $ ~/bin/python2.4 tern.py File "tern.py", line 5 x = 1 if True else 2 ^ SyntaxError: invalid syntax (channeling for a coworker)

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  • Porting WebGL game to iPhone's native OpenGL?

    - by ArtPulse
    We are developing a web game that uses WebGL for the two biggest parts of it. Working with HTML / CSS was too slow and too limited, so it's off the table. Thing is, iOS does not support WebGL publicly just yet, only on iAd. It is my guess Apple will eventually support it once the security issues they and Microsoft claim it has are fixed, and looks stable enough. Problem is, if Apple does not do this by the release of the next mayor iOS version, then we will have in our hands a mobile WebGL game that does not run. 6 months of development and testing to waste. So, questions: If that was the case, how viable (regarding amount of time) is it porting the WebGL part of the game to native iPhone OpenGL? I'm afraid that porting will take longer than the development of the game itself. I saw posts on Stack Overflow (like this) that suggested, on Android, adding the OpenGL interface manually to a WebKit element. It'd be slower than native. But either way... Is this something that could be accepted in the AppStore? Apple is very restrictive with these kind of stuff... Thank you all for your time!

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  • iPhone OS: Is there a way to set up KVO between two ManagedObject Entities?

    - by nickthedude
    I have 2 entities I want to link with KVO, one a single statTracker class that keeps track of different stats and the other an achievement class that contains information about achievements. Ideally what I want to be able to do is set up KVO by having an instance of the achievement class observe a value on the statTracker class and also set up a threshold value at which the achievement instance should be "triggered"(triggering in this case would mean showing a UIAlertView and changing a property on the achievement class.) I'd like to also set these relationships up on instantiation of the achievement class if possible so kind of like this: Achievement *achievement1 = (Achievement *)[NSEntityDescription insertNewObjectForEntityForName:@"Achievement" inManagedObjectContext:[[CoreDataSingleton sharedCoreDataSingleton] managedObjectContext]]; [achievement1 setAchievementName:@"2 time launcher"]; [achievement1 setAchievementDescription:@"So you've decided to come back for more eh? Here are some achievement points to get you going"]; [achievement1 setAchievementPoints:[NSNumber numberWithInt:300]; [achievement1 setObjectToObserve:@"statTrackerInstace" propertyToObserve:@"timesLaunched" valueOfPropertToSatisfyAchievement:2] Anyone out there know how I would set this up? Is there some way I could do this by way of relationships that I'm not seeing? Thanks, Nick

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  • Computing complex math equations in python

    - by dassouki
    Are there any libraries or techniques that simplify computing equations ? Take the following two examples: F = B * { [ a * b * sumOf (A / B ''' for all i ''' ) ] / [ sumOf(c * d * j) ] } where: F = cost from i to j B, a, b, c, d, j are all vectors in the format [ [zone_i, zone_j, cost_of_i_to_j], [..]] This should produce a vector F [ [1,2, F_1_2], ..., [i,j, F_i_j] ] T_ij = [ P_i * A_i * F_i_j] / [ SumOf [ Aj * F_i_j ] // j = 1 to j = n ] where: n is the number of zones T = vector [ [1, 2, A_1_2, P_1_2], ..., [i, j, A_i_j, P_i_j] ] F = vector [1, 2, F_1_2], ..., [i, j, F_i_j] so P_i would be the sum of all P_i_j for all j and Aj would be sum of all P_j for all i I'm not sure what I'm looking for, but perhaps a parser for these equations or methods to deal with multiple multiplications and products between vectors? To calculate some of the factors, for example A_j, this is what i use from collections import defaultdict A_j_dict = defaultdict(float) for A_item in TG: A_j_dict[A_item[1]] += A_item[3] Although this works fine, I really feel that it is a brute force / hacking method and unmaintainable in the case we want to add more variables or parameters. Are there any math equation parsers you'd recommend? Side Note: These equations are used to model travel. Currently I use excel to solve a lot of these equations; and I find that process to be daunting. I'd rather move to python where it pulls the data directly from our database (postgres) and outputs the results into the database. All that is figured out. I'm just struggling with evaluating the equations themselves. Thanks :)

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  • rotate an image aroound a point

    - by Girish
    Hi all, I have an image which is of rectangular dimension, eg 30 x 60 pixels I want to rotate this image around the bottom center of the image, i.e i want to set the pivot in the above example as (15, 60 )pixel. I am using a drawble and matrix to get this done, whatever i try i always end up rotating around center of the image. Code is : Bitmap bitmapOrg = BitmapFactory.decodeFile("/sdcard/DCIM/2010-06-01_15-32-42_821.jpg"); // float angle = (angle + 10.0f)%360.0f; if(null !=bitmapOrg) { int width = bitmapOrg.getWidth(); int height = bitmapOrg.getHeight(); int newWidth = 15; int newHeight = 15; // calculate the scale - in this case = 0.4f float scaleWidth = ((float) newWidth) / width; float scaleHeight = ((float) newHeight) / height; /* Canvas c = new Canvas(bitmapOrg); float px = ; float py; c.rotate(angle, px, py)*/ // createa matrix for the manipulation Matrix matrix = new Matrix(); // resize the bit map matrix.postScale(scaleWidth, scaleHeight); // rotate the Bitmap // matrix.postRotate(45); // recreate the new Bitmap Bitmap resizedBitmap = Bitmap.createBitmap(bitmapOrg, 0, 0, width, height, matrix, true); // make a Drawable from Bitmap to allow to set the BitMap // to the ImageView, ImageButton or what ever BitmapDrawable bmd = new BitmapDrawable(resizedBitmap); ImageView imageView = new ImageView(this); // set the Drawable on the ImageView imageView.setImageDrawable(bmd); // center the Image imageView.setScaleType(ScaleType.CENTER); // imageView.layout(100, 300, 0, 0); // linLayout.addView(imageView); // add ImageView to the Layout linLayout.addView(imageView, new AbsoluteLayout.LayoutParams( LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT, 10, 30 ) ); can anyone let me know how to get this rectified?

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  • URL "fragment identifier" semantics for HTML documents

    - by Pointy
    I've been working with a new installation of the "MoinMoin" wiki software. As I was playing with it, typing in mostly random test pages, I created a link with a fragment blah blah see also [[SomeStuff#whatever|some other stuff about whatever]] Then I needed to figure out how to create the anchor for that "whatever" fragment identifier. I don't recall having to do that with MediaWiki, so I had to dig around, but finally I found that MoinMoin has an "Anchor" macro: == Whatever == <<Anchor(whatever)>> Looking at the generated HTML, I was surprised to see an empty <span> tag with an "id" value of "whatever". I expected that it'd be an <a> tag with a "name" attribute of "whatever". I dug around and found the source, and there's a comment that says they changed it from an <a> tag in order to avoid some IE problem with <pre> sections. This confused me — not because of the IE thing, but because it looked to me as if their "fix" had left the whole anchor mechanism completely broken. Much to my surprise, however, further testing indicated that it worked fine. I wrote a test page with 300 <span> tags all with "id" values, and I further shocked myself when Firefox behaved exactly as I would have expected it to had I used <a> tags. It also worked when I changed all the <span> tags to <em>. So by this time, you're either as surprised as I was, or else you're thinking "how can somebody that dumb have so many reputation points?" If you're in the second category, is it really the case that I've been typing in HTML for about 15 years now — a lot of HTML — and it's somehow escaped my notice that browsers use the HTML fragment to find any sort of element with a matching "id"? mind status: blown

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  • categorize a set of phrases into a set of similar phrases

    - by Dingo
    I have a few apps that generate textual tracing information (logs) to log files. The tracing information is the typical printf() style - i.e. there are a lot of log entries that are similar (same format argument to printf), but differ where the format string had parameters. What would be an algorithm (url, books, articles, ...) that will allow me to analyze the log entries and categorize them into several bins/containers, where each bin has one associated format? Essentially, what I would like is to transform the raw log entries into (formatA, arg0 ... argN) instances, where formatA is shared among many log entries. The formatA does not have to be the exact format used to generate the entry (even more so if this makes the algo simpler). Most of the literature and web-info I found deals with exact matching, a max substring matching, or a k-difference (with k known/fixed ahead of time). Also, it focuses on matching a pair of (long) strings, or a single bin output (one match among all input). My case is somewhat different, since I have to discover what represents a (good-enough) match (generally a sequence of discontinuous strings), and then categorize each input entries to one of the discovered matches. Lastly, I'm not looking for a perfect algorithm, but something simple/easy to maintain. Thanks!

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  • Space-saving character encoding for japanese?

    - by Constantin
    In my opinion a common problem: character encoding in combination with a bitmap-font. Most multi-language encodings have an huge space between different character types and even a lot of unused code points there. So if I want to use them I waste a lot of memory (not only for saving multi-byte text - i mean specially for spaces in my bitmap-font) - and VRAM is mostly really valuable... So the only reasonable thing seems to be: Using an custom mapping on my texture for i.e. UTF-8 characters (so that no space is waste). BUT: This effort seems to be same with use an own proprietary character encoding (so also own order of characters in my texture). In my specially case I got texture space for 4096 different characters and need characters to display latin languages as well as japanese (its a mess with utf-8 that only support generall cjk codepages). Had somebody ever a similiar problem (I really wonder, if not)? If theres already any approach? Edit: The same Problem is described here http://www.tonypottier.info/Unicode_And_Japanese_Kanji/ but it doesnt provide an real solution how to save these bitmapfont mappings to utf-8 space efficent. So any further help is welcome!

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  • Is there a way to make changes to toggles in my .emacs file apply without re-starting Emacs?

    - by Vivi
    I want to be able to make the changes to my .emacs file without having to reload Emacs. I found three questions which sort of answer what I am asking (you can find them here, here and here), but the problem is that the change I have just made is to a toggle, and as the comments to two of the answers (a1, a2) to those questions explain, the solutions given there (such as M-x reload-file or M-x eval-buffer) don't apply to toggles. I imagine there is a way of toggling the variable again with a command, but if there is a way to reload the whole .emacs and have the all the toggles re-evaluated without having to specify them, I would prefer. In any case, I would also appreciate if someone told me how to toggle the value of a variable so that if I just changed one toggle I can do it with a command rather than re-start Emacs just for that (I am new to Emacs). I don't know how useful this information is, but the change I applied was the following (which I got from this answer to another question): (setq skeleton-pair t) (setq skeleton-pair-on-word t) (global-set-key (kbd "[") 'skeleton-pair-insert-maybe) (global-set-key (kbd "(") 'skeleton-pair-insert-maybe) (global-set-key (kbd "{") 'skeleton-pair-insert-maybe) (global-set-key (kbd "<") 'skeleton-pair-insert-maybe) Edit: I included the above in .emacs and reloaded Emacs, so that the changes took effect. Then I commented all of it out and tried M-x load-file. This doesn't work. The suggestion below (C-x C-e by PP works if I am using it to evaluate the toggle first time, but not when I want to undo it). I would like something that would evaluate the commenting out, if such thing exists... Thanks :)

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  • Putting BigDecimal data into HSQLDB test database using DbUnit

    - by Denise
    Hi everyone, I'm using Hibernate JPA in my backend. I am writing a unit test using JUnit and DBUnit to insert a set of data into an in-memory HSQL database. My dataset contains: <order_line order_line_id="1" quantity="2" discount_price="0.3"/> Which maps to an OrderLine Java object where the discount_price column is defined as: @Column(name = "discount_price", precision = 12, scale = 2) private BigDecimal discountPrice; However, when I run my test case and assert that the discount price returned equals 0.3, the assertion fails and says that the stored value is 0. If I change the discount_price in the dataset to be 0.9, it rounds up to 1. I've checked to make sure HSQLDB isn't doing the rounding and it definitely isn't because I can insert an order line object using Java code with a value like 5.3 and it works fine. To me, it seems like DBUtils is for some reason rounding the number I've defined. Is there a way I can force this to not happen? Can anyone explain why it might be doing this? Thanks!

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  • Set the selected item for a combobox in a datagrid

    - by JingJingTao
    I am using a datagrid which has many combobox fields in it, when I click the datagrid combobox the selected item or highlighted value is the last item in the list, but I would like it to highlight the first(top) item in the list. I know for just a combobox, all I need to do is change the combobox.selecteditem or combobox.selectedindex, but I'm not sure what to do in this case. I have binded the combobox to a table in the database and used a datatable to store the combobox values and then I add a row to the datatable, I think the reason the last item in the combobox is highlighted is because I added a row to the datatable. Thank you for your help. String strGetTypes = "SELECT holidaycodeVARCHAR4Pk, codedescVARCHAR45 FROM holidaytype ORDER BY holidaycodeVARCHAR4Pk Desc"; DataTable dtHolidayType = new DataTable(); MySqlDataAdapter dbaElements = new MySqlDataAdapter(strGetTypes, ShareSqlSettings.dbConnect); dbaElements.Fill(dtHolidayType); DataGridViewComboBoxCell cboxDays = new DataGridViewComboBoxCell(); cboxDays.DataSource = dtHolidayType; cboxDays.DisplayMember = "codedescVARCHAR45"; cboxDays.ValueMember = "holidaycodeVARCHAR4Pk"; //Blank row dtHolidayType.Rows.Add(1); // gridDailyEmp.Rows[j].Cells[day] = cboxDays;

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  • Messaging pattern question

    - by Al Bundy
    Process A is calculating values for objects a1, a2, a3 etc. and is sending results to the middleware queue (RabbitMQ). Consumers read the queue and process these results further. Periodically process A has to send a snapshot of these values, so consumers could do some other calculations. Values for these objects might change independently. The queue might look like this a1, a1, a2, a1, a2, a2, a3... Consumers process each item in the queue. The snapshot has to contain all objects and consumers will process this message for all objects in one go. So the requirement is to have a queue like this: a1, a1, a3, a2, a2, [snapshot, a1, a2, a3], a3, a1 ... The problem is that these items are of different types: one type for objects like a1, a2 and other for a snapshot. This means that they should be processed in a diferent queues, but in that case there is a race condition: consumers might process objects before processing a snapshot. Is there any pattern to solve this (quite common) problem? We are using RabbitMQ for message queueing.

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  • Simulating O_NOFOLLOW (2): Is this other approach safe?

    - by Daniel Trebbien
    As a follow-up question to this one, I thought of another approach which builds off of @caf's answer for the case where I want to append to file name and create it if it does not exist. Here is what I came up with: Create a temporary directory with mode 0700 in a system temporary directory on the same filesystem as file name. Create an empty, temporary, regular file (temp_name) in the temporary directory (only serves as placeholder). Open file name for reading only, just to create it if it does not exist. The OS may follow name if it is a symbolic link; I don't care at this point. Make a hard link to name at temp_name (overwriting the placeholder file). If the link call fails, then exit. (Maybe someone has come along and removed the file at name, who knows?) Use lstat on temp_name (now a hard link). If S_ISLNK(lst.st_mode), then exit. open temp_name for writing, append (O_WRONLY | O_APPEND). Write everything out. Close the file descriptor. unlink the hard link. Remove the temporary directory. (All of this, by the way, is for an open source project that I am working on. You can view the source of my implementation of this approach here.) Is this procedure safe against symbolic link attacks? For example, is it possible for a malicious process to ensure that the inode for name represents a regular file for the duration of the lstat check, then make the inode a symbolic link with the temp_name hard link now pointing to the new, symbolic link? I am assuming that a malicious process cannot affect temp_name.

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  • UI Automation Button Style Enabled

    - by Victor Gaspar
    Hi, I'm evaluating UI Automation for UI testing for that I have a WPF application with the following button defined: <Button Style="{DynamicResource ButtonStyle}" x:Name="MyBtn"/> when I need to visually disable the button I just change the style so the user is aware that the button is disabled (the colour changed) but still the button is internally enabled so I can still launch the OnClick event in order to show a message when the user clicks on a "disabled" button. Now the problem is that I don't know how to check from UI Automation the Style that its currently applied i.e. if the button is disabled or enabled. Do you know how can I do that? In a normal situation I should do something like that: Automation.Condition cEBtn = new PropertyCondition(AutomationElement.AutomationIdProperty, "MyBtn"); AutomationElement mybtnElement = appRegraceElement.FindFirst(TreeScope.Children, cEBtn); bool disMyBtn = (bool)mybtnElement .GetCurrentPropertyValue(AutomationElement.IsEnabledProperty); but in my case the button is always enabled therefore I need to check the Style applied to the button. Thank you very much. Best regards

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  • Qt/MFC Migration Framework tool: properly exiting DLL?

    - by User
    I'm using the Qt/MFC Migration Framework tool following this example: http://doc.qt.nokia.com/solutions/4/qtwinmigrate/winmigrate-qt-dll-example.html The dll I build is loaded by a 3rd party MFC-based application. The 3rd party app basically calls one of my exported DLL functions to startup my plugin and another function to shutdown my application. Currently I'm doing nothing in my shutdown function. When I load my DLL in the 3rd party app the startup function is called and my DLL starts successfully and I can see my message box. However if I shutdown my plugin and then try to start it again I get the following error: Debug Error! Program: <my 3rd party app> Module: 4.7.1 File: global\qglobal.cpp Line: 2262 ASSERT failure in QWidget: "Widgets must be created in the GUI thread.", file kernel\qwidget.cpp line 1233 (Press Retry to debug the application) Abort Retry Ignore This makes me think I'm not doing something to properly shutdown my plugin. What do I need to do to shut it down properly? UPDATE: http://doc.qt.nokia.com/solutions/4/qtwinmigrate/winmigrate-walkthrough.html says: The DLL also has to make sure that it can be loaded together with other Qt based DLLs in the same process (in which case a QApplication object will probably exist already), and that the DLL that creates the QApplication object remains loaded in memory to avoid other DLLs using memory that is no longer available to the process. So I wonder if there is some problem where I need to somehow keep the original DLL loaded no matter what?

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  • Algorithm possible amounts (over)paid for a specific price, based on denominations

    - by Wrikken
    In a current project, people can order goods delivered to their door and choose 'pay on delivery' as a payment option. To make sure the delivery guy has enough change customers are asked to input the amount they will pay (e.g. delivery is 48,13, they will pay with 60,- (3*20,-)). Now, if it were up to me I'd make it a free field, but apparantly higher-ups have decided is should be a selection based on available denominations, without giving amounts that would result in a set of denominations which could be smaller. Example: denominations = [1,2,5,10,20,50] price = 78.12 possibilities: 79 (multitude of options), 80 (e.g. 4*20) 90 (e.g. 50+2*20) 100 (2*50) It's international, so the denominations could change, and the algorithm should be based on that list. The closest I have come which seems to work is this: for all denominations in reversed order (large=>small) add ceil(price/denomination) * denomination to possibles baseprice = floor(price/denomination) * denomination; for all smaller denominations as subdenomination in reversed order add baseprice + (ceil((price - baseprice) / subdenomination) * subdenomination) to possibles end for end for remove doubles sort Is seems to work, but this has emerged after wildly trying all kinds of compact algorithms, and I cannot defend why it works, which could lead to some edge-case / new countries getting wrong options, and it does generate some serious amounts of doubles. As this is probably not a new problem, and Google et al. could not provide me with an answer save for loads of pages calculating how to make exact change, I thought I'd ask SO: have you solved this problem before? Which algorithm? Any proof it will always work?

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  • What's wrong with debugging in Eclipse on Android?

    - by Sebastian Dwornik
    I've obviously been spoiled by Visual Studio, because although I'm just learning Android and the Eclipse environment, debugging apps in Eclipse is becoming a serious detriment to further development. For example, Eclipse will compile this divide by zero just fine: public class Lesson2Main extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate (savedInstanceState); int i = 1 / 0; TextView tv = new TextView (this); tv.setText ("Hello, Android!"); setContentView (tv); } } And then, when it executes it under the debugger, I will get a full screen of useless debug info, non of which actually points me to the specific line containing the error. The stackTrace is null within the exception ('e') info tree, and it simply states a message stating 'ArithmeticException'. (that's nice, how about you point me in the direction of where you found it!?) I've looked all over the screen and am baffled that this IDE can't get this right. Does developing with Eclipse resort everyone back to 1991 with printf() like logging at every interval then to track down bugs? Seriously. Is there a configuration or plug-in that I'm missing to help with this? I haven't tested this case with XCode, but if the iPhone dev. IDE handles this more like Visual Studio, then no wonder the Android marketplace has so few apps. I'm excited about Android, but it seems that Eclipse is getting in the way.

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  • Where should you put 3rd party .NET dlls when using git submodules to avoid duplication

    - by Tim Abell
    I have two .NET library projects in Visual Studio 2008 that both make use of the MySql Connector for .NET (MySql.Data.dll). These libraries are then in turn both used by a .NET command line application which also uses the Connector. The library projects are pulled in to the application's solution as git submodules and referenced by project in Visual Studio. I'm looking for the most effective strategy for storing and referencing the MySql Connector library. I have tried having the MySql.Data.dll checked in to all three projects (in their root folder), this was problematic when one project changed to a newer version of the connector dll. Although each project had its own version of the dll, only one was packaged into the resultant application leading to an API mismatch which was hard to pin down. This has put me off this approach. I have tried having the command line application reference the connector dll that is held in a submodule, however this only removes the possibility of version mismatches when there is only one submodule rather than two as in this case. I am contemplating putting the dll in the global assembly cache (GAC) of all machines that need to build or use the application, but I'm wary of not having all dependencies for an application available in source control.

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  • what kind of relationship is there between a common wall and the rooms that located next to it?

    - by siamak
    I want to know whats the Relationship between a common wall (that are located In an adjoining room ) and the rooms. As i know the relationship between a room and its walls is Composition not Aggregation (am i right ?) And according to the definition of Composition the contained object can't be shared between two containers, whereas in aggregation it is possible. now i am confused that whats the best modeling approach to represent the relationship between a common wall and the rooms located next to it ? It would be highly Appreciated if you could provide your advices with some code. |--------|--------| Approch1: (wall class ---- room class) /Composition Approach2: wall class ----- room class /Aggregation Approch3: we have a wall class and a Common wall class , Common wall class inherits from wall class adjoining room class ---- (1) Common wall class /Aggregation adjoining room class ---- (6) wall class / composition Approach4: I am a developer not a designer :) so this is my idea : class Room { private wall _firstwall ; private wall _secondtwall; private wall _thirdwall ; private wall _commonwall ; public Room( CommonWall commonwall) { _firstwall=new Wall(); _secondtwall=new Wall(); _thirdwall=new Wall(); _commonwall=commonwall; } } Class CommonWall:Wall { //... } // in somewher : static void main() { Wall _commonWall=new Wall(); Room room1=new Room(_commonWall); Room room2=new Room(_commonWall); Room [] adjacentRoom =new Room[2]{room1,room2}; } Edit 1: I think this is a clear question but just for more clarification : The point of the question is to find out whats the best pattern or approach to model a relationship for an object that is a component of two other objects in the same time. and about my example : waht i mean by a "room" ?,surely i mean an enclosed square room with 4 walls and one door.but in this case one of these walls is a common wall and is shared between two adjacent rooms.

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  • How can I make a Maybe-Transformer MaybeT into an instance of MonadWriter?

    - by martingw
    I am trying to build a MaybeT-Transformer Monad, based on the example in the Real World Haskell, Chapter Monad Transformers: data MaybeT m a = MaybeT { runMT :: m (Maybe a) } instance (Monad m) => Monad (MaybeT m) where m >>= f = MaybeT $ do a <- runMT m case a of Just x -> runMT (f x) Nothing -> return Nothing return a = MaybeT $ return (Just a) instance MonadTrans MaybeT where lift m = MaybeT $ do a <- m return (Just a) This works fine, but now I want to make MaybeT an instance of MonadWriter: instance (MonadWriter w m) => MonadWriter w (MaybeT m) where tell = lift . tell listen m = MaybeT $ do unwrapped <- listen (runMT m) return (Just unwrapped) The tell is ok, but I can't get the listen function right. The best I could come up with after 1 1/2 days of constructor origami is the one you see above: unwrapped is supposed to be a tuple of (Maybe a, w), and that I want to wrap up in a Maybe-Type and put the whole thing in an empty MonadWriter. But the compiler complains with: Occurs check: cannot construct the infinite type: a = Maybe a When generalising the type(s) for `listen' In the instance declaration for `MonadWriter w (MaybeT m)' What am I missing?

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  • When do you tag your software project?

    - by WilhelmTell of Purple-Magenta
    I realize there are various kinds of software projects: commercial (for John Doe) industrial (for Mr. Montgomery Burns) successful open-source (with audience larger than, say, 10 people) personal projects (with audience size in the vicinity of 1). each of which release a new version of their product on difference conditions. I'm particularly interested in the case of personal projects and open-source projects. When, or under what conditions, do you make a new release of any kind? Do you subscribe to a fixed recurring deadline such as every two weeks? Do you commit to a release of at least 10 minor fixes, or one major fix? Do you combine the two conditions such as at least one condition must hold, or both must hold? I reckon this is a subjective question. I ask this question in light of searching for tricks to keep my projects alive and kicking. Sometimes my projects are active but look as if they aren't because I don't have the confidence to make a release or a tag of any sort for a long time -- in the order of months.

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  • casting Collection<SomeClass> to Collection<SomeSuperClass>

    - by skrebbel
    Hi all, I'm sure this has been answered before, but I really cannot find it. I have a java class SomeClass and an abstract class SomeSuperClass. SomeClass extends SomeSuperClass. Another abstract method has a method that returns a Collection<SomeSuperClass>. In an implementation class, I have a Collection<SomeClass> myCollection I understand that I cannot just return myCollection, because Collection<SomeClass> does not inherit from Collection<SomeSuperClass>. Nevertheless, I know that everything in myCollection is a SomeSuperClass because after all, they're SomeClass objects which extend SomeSuperClass. How can I make this work? I.e. I want public class A { private Collection<SomeClass> myCollection; public Collection<SomeSuperClass> getCollection() { return myCollection; //compile error! } } The only way I've found is casting via a non-generic type and getting unchecked warnings and whatnot. There must be a more elegant way, though? I feel that also using Collections.checkedSet() and friends are not needed, since it is statically certain that the returned collection only contains SomeClass objects (this would not be the case when downcasting instead of upcasting, but that's not what I'm doing). What am I missing? Thanks!

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  • Setting nested object to null when selected option has empty value

    - by Javi
    Hello, I have a Class which models a User and another which models his country. Something like this: public class User{ private Country country; //other attributes and getter/setters } public class Country{ private Integer id; private String name; //other attributes and getter/setters } I have a Spring form where I have a combobox so the user can select his country or can select the undefined option to indicate he doen't want to provide this information. So I have something like this: <form:select path="country"> <form:option value="">-Select one-</form:option> <form:options items="${countries}" itemLabel="name" itemValue="id"/> </form:select> In my controller I get the autopopulated object with the user information and I want to have country set to null when the "-Select one-" option has been selected. So I have set a initBinder with a custom editor like this: @InitBinder protected void initBinder(WebDataBinder binder) throws ServletException { binder.registerCustomEditor(Country.class, "country", new CustomCountryEditor()); } and my editor do something like this: public class CustomCountryEditor(){ @Override public String getAsText() { //I return the Id of the country } @Override public void setAsText(String str) { //I search in the database for a country with id = new Integer(str) //and set country to that value //or I set country to null in case str == null } } When I submit the form it works because when I have country set to null when I have selected "-Select one-" option or the instance of the country selected. The problem is that when I load the form I have a method like the following one to load the user information. @ModelAttribute("user") public User getUser(){ //loads user from database } The object I get from getUser() has country set to a specific country (not a null value), but in the combobox is not selected any option. I've debugged the application and the CustomCountryEditor works good when setting and getting the text, thoughgetAsText method is called for every item in the list "countries" not only for the "country" field. Any idea? Is there a better way to set null the country object when I select no country option in the combobox? Thanks

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