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• How to implement generic callbacks in C++

  - by Kylotan

  Forgive my ignorance in asking this basic question but I've become so used to using Python where this sort of thing is trivial that I've completely forgotten how I would attempt this in C++. I want to be able to pass a callback to a function that performs a slow process in the background, and have it called later when the process is complete. This callback could be a free function, a static function, or a member function. I'd also like to be able to inject some arbitrary arguments in there for context. (ie. Implementing a very poor man's coroutine, in a way.) On top of that, this function will always take a std::string, which is the output of the process. I don't mind if the position of this argument in the final callback parameter list is fixed. I get the feeling that the answer will involve boost::bind and boost::function but I can't work out the precise invocations that would be necessary in order to create arbitrary callables (while currying them to just take a single string), store them in the background process, and invoke the callable correctly with the string parameter.

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• Avoid loading unnecessary data from db into objects (web pages)

  - by GmGr

  Really newbie question coming up. Is there a standard (or good) way to deal with not needing all of the information that a database table contains loaded into every associated object. I'm thinking in the context of web pages where you're only going to use the objects to build a single page rather than an application with longer lived objects. For example, lets say you have an Article table containing id, title, author, date, summary and fullContents fields. You don't need the fullContents to be loaded into the associated objects if you're just showing a page containing a list of articles with their summaries. On the other hand if you're displaying a specific article you might want every field loaded for that one article and maybe just the titles for the other articles (e.g. for display in a recent articles sidebar). Some techniques I can think of: Don't worry about it, just load everything from the database every time. Have several different, possibly inherited, classes for each table and create the appropriate one for the situation (e.g. SummaryArticle, FullArticle). Use one class but set unused properties to null at creation if that field is not needed and be careful. Give the objects access to the database so they can load some fields on demand. Something else? All of the above seem to have fairly major disadvantages. I'm fairly new to programming, very new to OOP and totally new to databases so I might be completely missing the obvious answer here. :)

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• CALayer and Off-Screen Rendering

  - by Luke Mcneice

  I have a Paging UIScrollView with a contentSize large enough to hold a number of small UIScrollViews for zooming, The viewForZoomingInScrollView is a viewController that holds a CALayer for drawing a PDF page onto. This allows me to navigate through a PDF much like the ibooks PDF reader. The code that draws the PDF (Tiled Layers) is located in: - (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx; And simply adding a 'page' to the visible screen calls this method automatically. When I change page there is some delay before all the tiles are drawn, even though the object (page) has already been created. What i want to be able to do is render the next page before the user scrolls to it, thus preventing the visible tiling effect. However, i have found that if the layer is located offscreen adding it to the scrollview doesn't call the drawLayer. Any Ideas/common gotchas here? I have tried: [viewController.view.layer setNeedsLayout]; [viewController.view.layer setNeedsDisplay]; NB: The fact that this is replicating the ibooks functionally is irrelevant within the context of the full app.

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• Passing filtering functions to Where() in LINQ-to-SQL

  - by Daniel

  I'm trying to write a set of filtering functions that can be chained together to progressively filter a data set. What's tricky about this is that I want to be able to define the filters in a different context from that in which they'll be used. I've gotten as far as being able to pass a very basic function to the Where() clause in a LINQ statement: filters file: Func<item, bool> returnTrue = (i) => true; repository file: public IQueryable<item> getItems() { return DataContext.Items.Where(returnTrue); } This works. However, as soon as I try to use more complicated logic, the trouble begins: filters file: Func<item, bool> isAssignedToUser = (i) => i.assignedUserId == userId; repository file: public IQueryable<item> getItemsAssignedToUser(int userId) { return DataContext.Items.Where(isAssignedToUser); } This won't even build because userId isn't in the same scope as isAssignedToUser(). I've also tried declaring a function that takes the userId as a parameter: Func<item, int, bool> isAssignedToUser = (i, userId) => i.assignedUserId == userId; The problem with this is that it doesn't fit the function signature that Where() is expecting: Func<item, bool> There must be a way to do this, but I'm at a loss for how. I don't feel like I'm explaining this very well, but hopefully you get the gist. Thanks, Daniel

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• Use XML Layout to contain a simple drawing

  - by user329999

  I would like to create a simple drawing (lines, circles, squares, etc...) but I'm having difficulty figuring out the best way to do this. The drawing would need to be scaled to fit the display since the size is indirectly specified by the user (like in a CAD application). Also, I don't want to take up the entire display, leaving room for some controls (buttons, etc). I would pass the data to describe the drawing. Here's how I imagine it would work. I create an XML layout that contains something that holds the drawing (ImageView, BitmapDrawable, ShapeDrawable, ...??? not sure exactly what). Then in my Activity I would load the main XML and obtain the resource for the control that holds the drawing. I would then draw to a bitmap. Once the bitmap was completed I would load it into the control that is to hold the drawing. Somewhere along this path it would be scaled to fill the entire area allocated for the drawing in the XML layout. I don't know if my approach is the way to do this or what classes to use. I read the http://developer.android.com/guide/topics/graphics/2d-graphics.html documentation, but it's not helping me with an example. The examples I do find leave me with hints, but nothing concrete enough to do what I want, especially when it comes to scaling, using XML and/or having other controls. Also, there seems to be no good documentation on the design of the 2D drawing system in a more conceptual manner, so it makes what I read difficult to put into any useful context. Any hints on what classes would be useful and/or a good example any other reading materials? Thanks

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• Float addition promoted to double?

  - by Andreas Brinck

  I had a small WTF moment this morning. Ths WTF can be summarized with this: float x = 0.2f; float y = 0.1f; float z = x + y; assert(z == x + y); //This assert is triggered! (Atleast with visual studio 2008) The reason seems to be that the expression x + y is promoted to double and compared with the truncated version in z. (If i change z to double the assert isn't triggered). I can see that for precision reasons it would make sense to perform all floating point arithmetics in double precision before converting the result to single precision. I found the following paragraph in the standard (which I guess I sort of already knew, but not in this context): 4.6.1. "An rvalue of type float can be converted to an rvalue of type double. The value is unchanged" My question is, is x + y guaranteed to be promoted to double or is at the compiler's discretion? UPDATE: Since many people has claimed that one shouldn't use == for floating point, I just wanted to state that in the specific case I'm working with, an exact comparison is justified. Floating point comparision is tricky, here's an interesting link on the subject which I think hasn't been mentioned.

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• Android, NetworkInfo.getTypeName(), NullpointerException

  - by moppel

  I have an activity which shows some List entries. When I click on a list item my app checks which connection type is available ("WIF" or "MOBILE"), through NetworkInfo.getTypeName(). As soon as I call this method I get a NullpointerException. Why? I tested this on the emulator, cause my phone is currently not available (it's broken...). I assume this is the problem? This is the only explanation that I have, if that's not the case I have no idea why this would be null. Here's some code snippet: public class VideoList extends ListActivity{ ... public void onCreate(Bundle bundle){ final ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); ... listview.setOnItemClickListener(new OnItemClickListener(){ public void onItemClick(AdapterView<?> parent, View view, int position, long id) { ... NetworkInfo ni = cm.getActiveNetworkInfo(); String connex = ni.getTypeName(); //Nullpointer exception here if(connex.equals("WIFI")doSomething(); } }); } }

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• Set HttpContext.Current.User from Thread.CurrentPrincipal

  - by Argons

  I have a security manager in my application that works for both windows and web, the process is simple, just takes the user and pwd and authenticates them against a database then sets the Thread.CurrentPrincipal with a custom principal. For windows applications this works fine, but I have problems with web applications. After the process of authentication, when I'm trying to set the Current.User to the custom principal from Thread.CurrentPrincipal this last one contains a GenericPrincipal. Am I doing something wrong? This is my code: Login.aspx protected void btnAuthenticate_Click(object sender, EventArgs e) { Authenticate("user","pwd"); FormsAuthenticationTicket authenticationTicket = new FormsAuthenticationTicket(1, "user", DateTime.Now, DateTime.Now.AddMinutes(30), false, ""); string ticket = FormsAuthentication.Encrypt(authenticationTicket); HttpCookie authenticationCookie = new HttpCookie(FormsAuthentication.FormsCookieName, ticket); Response.Cookies.Add(authenticationCookie); Response.Redirect(FormsAuthentication.GetRedirectUrl("user", false)); } Global.asax (This is where the problem appears) protected void Application_AuthenticateRequest(object sender, EventArgs e) { HttpCookie authCookie = Context.Request.Cookies[FormsAuthentication.FormsCookieName]; if (authCookie == null) return; if (HttpContext.Current.User != null && HttpContext.Current.User.Identity.IsAuthenticated && HttpContext.Current.User.Identity is FormsIdentity) { HttpContext.Current.User = System.Threading.Thread.CurrentPrincipal; //Here the value is GenericPrincipal } Thanks in advance for any help. }

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• Ruby -- looking for some sort of "Regexp unescape" method

  - by RubyNoobie

  I have a bunch of strings that appear to have been double-escaped -- eg, I have "\\014\"\\000\"\\016smoothing\"\\011mean\"\\022color\"\\011zero@\\016" but I want "\014"\000"\016smoothing"\011mean"\022color"\011zero@\016" Is there a method I can use to unescape them? I imagine that I could make a regex to remove 1 backslash from every consecutive n backslashes, but I don't have a lot of regex experience and it seems there ought to be a "more elegant" way to do it. For example, when I puts MyString it displays the output I'd like, but I don't know how I might capture that into a variable. Thanks! Edited to add context: I have this class that is being used to marshal / restore some stuff, but when I restore some old strings it spits out a type error which I've determined is because they weren't -- for some inexplicable reason -- stored as base64. They instead appear to be 'double-escaped', when I need them to be 'single-escaped' to get restored. require 'base64' class MarshaledStuff < ActiveRecord::Base validates_presence_of :marshaled_obj def contents obj = self.marshaled_obj return Marshal.restore(Base64.decode64(obj)) end def contents=(newcontents) self.marshaled_obj = Base64.encode64(Marshal.dump(newcontents)) end end

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• Android SDK: hello world does not run

  - by Alex

  I have installed Java x64, Eclipse Classic Judo x64 + ADT Pluggin. OS win 7 x64. I did installation everything according to the manual. Then created first application and launched it. Emulator was launched but hello world was not. I have not idea what doing wrong. Do anyone knows of such error and my problem as a whole? thx Console log: [2012-10-06 13:35:42 - test] ------------------------------ [2012-10-06 13:35:42 - test] Android Launch! [2012-10-06 13:35:42 - test] adb is running normally. [2012-10-06 13:35:42 - test] Performing com.example.test.MainActivity activity launch [2012-10-06 13:35:42 - test] Automatic Target Mode: launching new emulator with compatible AVD 'AVD_41' [2012-10-06 13:35:42 - test] Launching a new emulator with Virtual Device 'AVD_41' [2012-10-06 13:35:42 - Emulator] Failed to create Context 0x3005 [2012-10-06 13:35:42 - Emulator] emulator: WARNING: Could not initialize OpenglES emulation, using software renderer. [2012-10-06 13:35:42 - Emulator] WARNING: Data partition already in use. Changes will not persist! [2012-10-06 13:35:42 - Emulator] WARNING: SD Card image already in use: C:\Users\Zewisa\.android\avd\AVD_41.avd/sdcard.img [2012-10-06 13:35:42 - Emulator] WARNING: Cache partition already in use. Changes will not persist! [2012-10-06 13:35:42 - Emulator] could not get wglGetExtensionsStringARB [2012-10-06 13:35:42 - Emulator] could not get wglGetExtensionsStringARB [2012-10-06 13:35:42 - Emulator] could not get wglGetExtensionsStringARB [2012-10-06 13:35:42 - Emulator] could not get wglGetExtensionsStringARB [2012-10-06 13:35:42 - Emulator] could not get wglGetExtensionsStringARB [2012-10-06 13:35:42 - Emulator] could not get wglGetExtensionsStringARB [2012-10-06 13:35:42 - Emulator] could not get wglGetExtensionsStringARB [2012-10-06 13:35:42 - Emulator] could not get wglGetExtensionsStringARB [2012-10-06 13:35:42 - Emulator] emulator: warning: opening audio input failed [2012-10-06 13:35:42 - Emulator]

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• CGLIB proxy error after spring bean definition loading into XmlWebApplicationContext at runtime

  - by VasylV

  I load additional singleton beans definitions at runtime from external jar file into existing XmlWebApplicationContext of my application: BeanFactory beanFactory = xmlWebApplicationContext.getBeanFactory(); DefaultListableBeanFactory defaultFactory = (DefaultListableBeanFactory)beanFactory; final URL url = new URL("external.jar"); final URL[] urls = {url}; ClassLoader loader = new URLClassLoader(urls, this.getClass().getClassLoader()); defaultFactory.setBeanClassLoader(loader); final ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(defaultFactory); final DefaultResourceLoader resourceLoader = new DefaultResourceLoader(); resourceLoader.setClassLoader(loader); scanner.setResourceLoader(resourceLoader); scanner.scan("com.*"); Object bean = xmlWebApplicationContext.getBean("externalBean"); After all above xmlWebApplicationContext contains all external definitions of beans. But when i am trying to get bean from context exception is thrown: Couldn't generate CGLIB proxy for class ... I saw in debug mode that in the bean initialization process first time proxy is generated by org.springframework.aop.aspectj.autoproxy.AspectJAwareAdvisorAutoProxyCreator and than it is tried to generate proxy with org.springframework.aop.framework.autoproxy.BeanNameAutoProxyCreator but fails with mentioned exception.

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• how to make the user add and delete in android

  - by user3678019

  i have 1 activity .. and in this activity i have 2 web view next to each other , i would like to add , ADD and Delete Button that can add one more web view next to the last web view , and the delete wish will delete any of the web view the user choose . and i want to make the user but it in the order he want like webview 1 first then webview 2 second how can i do this this is mu main.xml <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="test.zezo.test.Main$PlaceholderFragment" > <HorizontalScrollView android:id="@+id/horizontalScrollView2" android:layout_width="match_parent" android:layout_height="match_parent" android:layout_alignParentLeft="true" android:layout_alignParentRight="true" android:layout_alignParentTop="true" > <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" > <WebView android:id="@+id/webView1" android:layout_width="350dp" android:layout_height="match_parent" android:layout_alignParentLeft="true" /> <WebView android:id="@+id/webView22" android:layout_width="350dp" android:layout_height="match_parent" android:layout_toRightOf="@+id/webView1" android:layout_alignParentLeft="true" /> </LinearLayout> </HorizontalScrollView> and this is a part of my main.java webView = (WebView) findViewById(R.id.webView1); String url = "http://google.com"; webView.getSettings().setJavaScriptEnabled(true); webView.loadUrl(url); webView.setWebChromeClient(new WebChromeClient()); webView.setWebViewClient(new WebViewClient()); WebView webView22 = (WebView)findViewById(R.id.webView22); webView22.getSettings().setJavaScriptEnabled(true); webView22.loadUrl("google.com); webView22.setWebChromeClient(new WebChromeClient()); webView22.setWebViewClient(new WebViewClient()); so how can i do the ADD and DELETE and re Order Buttons to it and one more thing it should be save so when he reopen the app it will be the same as after he add or delete or re order

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• IIS not responding to the few requests from the client

  - by Haroon

  I am stuck with an issue with IIS 7.0. I need someone's help to find resolution on this, as this is very urgent requirement for us. Scenario I am trying to host the service in my server (Windows Server 2008 R2 and IIS 7.0) and my client is running in the XP machine with IIS 5.1. Few of my request sent from client get successful response and for few request I am getting the below exception in Visual studio when I try to debug. Exception in Visual studio 2010 An error occurred while receiving the HTTP response to This could be due to the service endpoint binding not using the HTTP protocol. This could also be due to HTTP request context being aborted by the server (possibly due to the service shutting down). See the server logs for more details. When referred to the server event viewer log I got the below events(Application error and System warning) during the above exception. Under System logs - Warning A process serving application pool 'DefaultAppPool' suffered a fatal communication error with the Windows Process Activation Service. The process id was '5372'. The data field contains the error number. Under Application log - Error Faulting application name: w3wp.exe, version: 7.5.7600.16385, time stamp: 0x4a5bd0eb Faulting module name: ntdll.dll, version: 6.1.7600.16559, time stamp: 0x4ba9b802 Exception code: 0xc0000374 Fault offset: 0x00000000000c6df2 Faulting process id: 0x14fc Faulting application start time: 0x01cbd042562e92c3 Faulting application path: c:\windows\system32\inetsrv\w3wp.exe Faulting module path: C:\Windows\SYSTEM32\ntdll.dll Report Id: 95f76467-3c35-11e0-a46e-7071bc5cc1ee From internet I am not able to get the exact solution. Therefore could anyone please help me out from getting resolution for the same that would be really a great help for me. Please let me know if you need more details. Thanks in advance.

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• MS CRM 4.0 Remove inactive account from another list

  - by Ekaterina

  Hi, I have the following problem, on which I can't seem to find an answer... I have a CRM 4.0 system and I want to achieve the following: When I have a contact/account that's inactive to remove it from another list, for example the Marketing list. So I already have everything, up to the removing part. I have a collection with the inactive accounts/contacts (The ID's(GUID)), I just need to remove somehow the member from the list. So there is a class RemoveMemberListRequest which looks like the correct one, the only problem is, somehow I can't get it to work. foreach (Guid currentMember in inactiveMembers) { RemoveMemberListRequest req = new RemoveMemberListRequest(); req.ListId = context.PrimaryEntityId; req.EntityId = currentMember ; RemoveMemberListResponse rmlResp = (RemoveMemberListResponse)crmService.Execute(req); } When It tries to Execute, the request it fails, with very generic error, that it was unable to execute the request. I am also not sure if that's the correct way of doing it... There is another class that seems to have a property that might be useful: QualifyMemberListRequest With property: OverrideorRemove But I don't really understand how this one works, and I couldn't find enough information. Anybody?

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• jquery: Writing a method

  - by Mark

  This is the same question as this: http://stackoverflow.com/questions/2890620/jquery-running-a-function-in-a-context-and-adding-to-a-variable But that question was poorly posed. Trying again, I'm trying to do something like this: I have a bunch of elements I want to grab data from, the data is in the form of classes of the element children. <div id='container'> <span class='a'></span> <span class='b'></span> <span class='c'></span> </div> <div id='container2'> <span class='1'></span> <span class='2'></span> <span class='3'></span> </div> I have a method like this: jQuery.fn.grabData = function(expr) { return this.each(function() { var self = $(this); self.find("span").each(function (){ var info = $(this).attr('class'); collection += info; }); }); }; I to run the method like this: var collection = ''; $('#container').grabData(); $('#container2').grabData(); The collection should be adding to each other so that in the end I get this console.log(collection); : abc123 But collection is undefined in the method. How can I let the method know which collection it should be adding to? Thanks.

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• Why would I need a using statement to Libary B extn methods, if they're used in Library A & it's Li

  - by Greg

  Hi, I have: Main Program Class - uses Library A Library A - has partial classes which mix in methods from Library B Library B - mix in methods & interfaces Why would I need a using statement to LibaryB just to get their extension methods working in the main class? That is given that it's Library B that defines the classes that will be extended. EDIT - Except from code // *** PROGRAM *** using TopologyDAL; using Topology; // *** THIS WAS NEEDED TO GET EXTN METHODS APPEARING *** class Program { static void Main(string[] args) { var context = new Model1Container(); Node myNode; // ** trying to get myNode mixin methods to appear seems to need using line to point to Library B *** } } // ** LIBRARY A namespace TopologyDAL { public partial class Node { // Auto generated from EF } public partial class Node : INode<int> // to add extension methods from Library B { public int Key } } // ** LIBRARY B namespace ToplogyLibrary { public static class NodeExtns { public static void FromNodeMixin<T>(this INode<T> node) { // XXXX } } public interface INode<T> { // Properties T Key { get; } // Methods } }

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• Visual Studio + Database Edition + CDC = Deploy Fail

  - by Ben

  Hi All, I've got a database using change data capture (CDC) that is created from a Visual Studio database project (GDR2). My problem is that I have a stored procedure that is analyzing the CDC information and then returning data. How is that a problem you ask? Well, the order of operation is as follows. Pre-deployment Script Tables Indexes, keys, etc. Procedures Post-deployment Script Inside the post-deployment script is where I enable CDC. Here-in lies the problem. The procedure that is acting on the CDC tables is bombing because they don't exist yet! I've tried to put the call to sys.sp_cdc_enable_table in the script that creates the table, but it doesn't like that. Error 102 TSD03070: This statement is not recognized in this context. C:...\Schema Objects\Schemas\dbo\Tables\Foo.table.sql 20 1 Foo Is there a better/built-in way to enable CDC such that it's references are available when the stored procedures are created? Is there a way to run a script after tables are created but before other objects are created? How about a way to create the procedure dependencies be damned? Or maybe I'm just doing things that shouldn't be done?!?! Now, I have a work around. Comment out the sproc body Deploy (CDC is created) Uncomment sproc Deploy Everything is great until the next time I update a CDC tracked table. Then I need to comment out the 'offending' procedure. Thanks for reading my question and thanks for your help!

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• Multi-account sync with Dropbox API

  - by Dan

  I'm trying to create a web app that lets users share files with each other through Dropbox. At the moment, Dropbox handles all the sharing, and there's one central Dropbox account running on the web server that shares the folder with the people who want it. I'm trying to change it so people don't have to accept a new folder invitation each time. I'd like to have them authorize my app to access an app folder in their Dropbox account, and all their shared folders would go inside there. Any changes they make would get noticed by the app on the server and synced to everyone else's folders. There's a couple things I'm having trouble figuring out to make this work: Do I need to make repeated calls to /delta for every account? I can't think how else I'd do this, but that sounds like it would quickly turn into thousands of requests a minute just polling for updates. When someone adds a file, do I have to upload it once for each account? That seems like a huge waste of bandwidth. I've looked into using /copy_ref, which I think would add a file to another user's account without my app ever touching it, but my app's web interface also allows users to upload files directly to my server, which would then need to be synced with everyone else's folders. That file isn't on Dropbox's servers yet, so /copy_ref obviously wouldn't work. For a little extra context, my app is written in node.js, and I've been playing with this library to interface with Dropbox, which uses their REST API.

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• Update database settings in properties file in Spring

  - by mvg

  Hi all, I am trying to create a Database Manager page which shows the database details on page load and updates the database settings when the user press submit I followed this tutorial and set the database settings in properties file. I managed to update the database settings in properties file programmatically. When I retrieved the database settings using the following code DriverManagerDataSource databaseSource = (DriverManagerDataSource)context.getBean("dataSource"); databaseSource.getUsername(); I managed to get the old value and unable to get the new value This is the mapping in applicationContext.xml file <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> <property name="location"> <value>classpath:/bundle/database.properties</value> </property> </bean> <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"> <property name="driverClassName" value="${jdbc.driverClassName}" /> <property name="url" value="${jdbc.url}" /> <property name="username" value="${jdbc.username}" /> <property name="password" value="${jdbc.password}" /> </bean> I checked the properties file and found it to be updated with the latest input. What am I missing? Thanks in advance P.S I am using JSF1.2 with Spring 3 Update Just making my requirement simple. I am creating a setparate dbsettings page, so that when user wishes to connect to different database he/she can just enter the details in dbsettings page and connect

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• Calling a subclass method from a superclass

  - by Shaun

  Preface: This is in the context of a Rails application. The question, however, is specific to Ruby. Let's say I have a Media object. class Media < ActiveRecord::Base end I've extended it in a few subclasses: class Image < Media def show # logic end end class Video < Media def show # logic end end From within the Media class, I want to call the implementation of show from the proper subclass. So, from Media, if self is a Video, then it would call Video's show method. If self is instead an Image, it would call Image's show method. Coming from a Java background, the first thing that popped into my head was 'create an abstract method in the superclass'. However, I've read in several places (including Stack Overflow) that abstract methods aren't the best way to deal with this in Ruby. With that in mind, I started researching typecasting and discovered that this is also a relic of Java thinking that I need to banish from my mind when dealing with Ruby. Defeated, I started coding something that looked like this: def superclass_method # logic this_media = self.type.constantize.find(self.id) this_media.show end I've been coding in Ruby/Rails for a while now, but since this was my first time trying out this behavior and existing resources didn't answer my question directly, I wanted to get feedback from more-seasoned developers on how to accomplish my task. So, how can I call a subclass's implementation of a method from the superclass in Rails? Is there a better way than what I ended up (almost) implementing?

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• How to transform a production to LL(1) for a list separated by a semicolon?

  - by Subb

  Hi, I'm reading this introductory book on parsing (which is pretty good btw) and one of the exercice is to "build a parser for your favorite language." Since I don't want to die today, I thought I could do a parser for something relatively simple, ie a simplified CSS. Note: This book teach you how to right a LL(1) parser using the recursive-descent algorithm. So, as a sub-exercice, I am building the grammar from what I know of CSS. But I'm stuck on a production that I can't transform in LL(1) : //EBNF block = "{", declaration, {";", declaration}, [";"], "}" //BNF <block> =:: "{" <declaration> "}" <declaration> =:: <single-declaration> <opt-end> | <single-declaration> ";" <declaration> <opt-end> =:: "" | ";" This describe a CSS block. Valid block can have the form : { property : value } { property : value; } { property : value; property : value } { property : value; property : value; } ... The problem is with the optional ";" at the end, because it overlap with the starting character of {";", declaration}, so when my parser meet a semicolon in this context, it doesn't know what to do. The book talk about this problem, but in its example, the semicolon is obligatory, so the rule can be modified like this : block = "{", declaration, ";", {declaration, ";"}, "}" So, Is it possible to achieve what I'm trying to do using a LL(1) parser?

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• Breeze Expand not working on WebAPI with EF

  - by Rodney

  I have published a WebAPI service which returns a list of items. I am implementing Breeze and have managed to get it basically working with filtering/sorting. However, the Expand is not working. http://www.ftter.com/desktopmodules/framework/api/dare/dares/?$filter=DareId%20eq%2010&expand%20eq%20ToUser You can see the ToUserId ForeignKey in the response above, but the ToUser properties are NULL (the user definitely exists) You can see the ToUser EF navigation property in the metadata. When I use .Include on the server side I can populate it with EF, but I don't want to do this. [HttpGet] [Queryable(AllowedQueryOptions = AllowedQueryOptions.All)] public HttpResponseMessage Dares() { var response = Request.CreateResponse(HttpStatusCode.OK, (IQueryable<Dare>)contextProvider.Context.Dares); return ControllerUtilities.GetResponseWithCorsHeader(response); } and here is the generated class from my EF model (using Database First) public partial class Dare { public int DareId { get; set; } public int ToUserId { get; set; } public virtual User ToUser { get; set; } }

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• Modeling complex hierarchies

  - by jdn

  To gain some experience, I am trying to make an expert system that can answer queries about the animal kingdom. However, I have run into a problem modeling the domain. I originally considered the animal kingdom hierarchy to be drawn like -animal -bird -carnivore -hawk -herbivore -bluejay -mammals -carnivores -herbivores This I figured would allow me to make queries easily like "give me all birds", but would be much more expensive to say "give me all carnivores", so I rewrote the hierarchy to look like: -animal -carnivore -birds -hawk -mammals -xyz -herbivores -birds -bluejay -mammals But now it will be much slower to query "give me all birds." This is of course a simple example, but it got me thinking that I don't really know how to model complex relationships that are not so strictly hierarchical in nature in the context of writing an expert system to answer queries as stated above. A directed, cyclic graph seems like it could mathematically solve the problem, but storing this in a relational database and maintaining it (updates) would seem like a nightmare to me. I would like to know how people typically model such things. Explanations or pointers to resources to read further would be acceptable and appreciated.

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• Why would ASP.NET MVC use session state?

  - by ray247

  Recommended by the ASP.NET team to use cache instead of session, we stopped using session from working with the WebForm model the last few years. So we normally have the session turned off in the web.config <sessionState mode="Off" /> But, now when I'm testing out a ASP.NET MVC application with this setting it throw an error in class SessionStateTempDataProvider inside the mvc framework, it asked me to turn on session state, I did and it worked. Looking at the source it uses session Dictionary<string, object> tempDataDictionary = httpContext.Session[TempDataSessionStateKey] as Dictionary<string, object>; // line 20 in SessionStateTempDataProvider.cs So, why would they use session here? What am I missing? Thanks, Ray. ======================================================== Edit Sorry didn't mean for this post to debate on session vs. cache, but rather in the context of the ASP.NET MVC, I was just wondering why session is used here. In this Scott Watermasysk blog post he mentioned on turning off session too as a good practice, so I'm just wondering do I have to turn it on to use MVC from here on?

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• Web-app currency input/manipulation/calculation with javascript .. there has got to be a better (fra

  - by dreftymac

  BACKGROUND: I am of the "user-input-lockdown" school of thought. Whenever possible, I try to mistrust and sanitize user input, both client side and server side; and I try to take multiple opportunities to restrict possible inputs to a known subset of possibilities, usually this means providing a lot of checkboxes and select lists. (This is from the usability side of things, I know security-wise that malicious users can easily bypass fixed user input GUI controls). PROBLEM: Anyway, the problem always arises with non-fixed input of currency. Whenever I have to accept a freely-specified dollar amount as user input, I always have to confront these problems/annoyances and it is always painful: 1) Make sure to give the user two input boxes for each currency_datapoint, one for the whole_dollar_part and another for the fractional_pennies_part 2) Whenever the user changes a currency_datapoint, provide keystroke-by-keystroke GUI feedback to let them know whether the currency_datapoint is well-formed, with context-appropriate validation rules (e.g., no negatives?, nonzero only?, numeric only!, no non-numeric punctuation! no symbols!) 3) For display purposes, every user-provided currency_datapoint should be translated to human-readable currency formatting (dollar sign, period, commas provided by the app, where appropriate) 4) For calculation purposes, every user-provided currency_datapoint has to be converted to integer (all pennies, to avoid floating point errors) and summed into a grand total with zero or more subtotals. 5) Every user-provided currency_datapoint should be displayed or displayable in a nice "tabular" format, which auto-updates as the user enters each currency_datapoint, including a baloon that warns when one or more currency_datapoints is not well-formed. I seem to be re-inventing this wheel every time I have to work with currency in Javascript on the client side (server side is a bit more flexible since most programming languages have higher-level currency formatting logic). QUESTION: Has anyone out there solved the problem of dealing with the above issues, client side, in a way that is server-side-technology-stack agnostic, (preferrably plain javascript or jquery)? This is getting old, there has to be a better way.

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