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• Hibernate Communications Link Failure in Restlet-Hibernate Based Java application powered by MySQL

  - by Vatsala

  Let me describe my question - I have a Java application - Hibernate as the DB interfacing layer over MySQL. I get the communications link failure error in my application. The occurence of this error is a very specific case. I get this error , When I leave mysql server unattended for more than approximately 6 hours (i.e. when there are no queries issued to MySQL for more than approximately 6 hours). I am pasting a top 'exception' level description below, and adding a pastebin link for a detailed stacktrace description. javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: Cannot open connection - Caused by: org.hibernate.exception.JDBCConnectionException: Cannot open connection - Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure - The last packet successfully received from the server was 1,274,868,181,212 milliseconds ago. The last packet sent successfully to the server was 0 milliseconds ago. - Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure - The last packet successfully received from the server was 1,274,868,181,212 milliseconds ago. The last packet sent successfully to the server was 0 milliseconds ago. - Caused by: java.net.ConnectException: Connection refused: connect the link to the pastebin for further investigation - http://pastebin.com/4KujAmgD What I understand from these exception statements is that MySQL is refusing to take in any connections after a period of idle/nil activity. I have been reading up a bit about this via google search, and came to know that one of the possible ways to overcome this is to set values for c3p0 properties as c3p0 comes bundled with Hibernate. Specifically, I read from here http://www.mchange.com/projects/c3p0/index.html that setting two properties idleConnectionTestPeriod and preferredTestQuery will solve this for me. But these values dont seem to have had an effect. Is this the correct approach to fixing this? If not, what is the right way to get over this? The following are related Communications Link Failure questions at stackoverflow.com, but I've not found a satisfactory answer in their answers. http://stackoverflow.com/questions/2121829/java-db-communications-link-failure http://stackoverflow.com/questions/298988/how-to-handle-communication-link-failure Note 1 - i dont get this error when I am using my application continuosly. Note 2 - I use JPA with Hibernate and hence my hibernate.dialect,etc hibernate properties reside within the persistence.xml in the META-INF folder (does that prevent the c3p0 properties from working?)

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• Implementing Skip List in C++

  - by trikker

  [SOLVED] So I decided to try and create a sorted doubly linked skip list... I'm pretty sure I have a good grasp of how it works. When you insert x the program searches the base list for the appropriate place to put x (since it is sorted), (conceptually) flips a coin, and if the "coin" lands on a then that element is added to the list above it(or a new list is created with element in it), linked to the element below it, and the coin is flipped again, etc. If the "coin" lands on b at anytime then the insertion is over. You must also have a -infinite stored in every list as the starting point so that it isn't possible to insert a value that is less than the starting point (meaning that it could never be found.) To search for x, you start at the "top-left" (highest list lowest value) and "move right" to the next element. If the value is less than x than you continue to the next element, etc. until you have "gone too far" and the value is greater than x. In this case you go back to the last element and move down a level, continuing this chain until you either find x or x is never found. To delete x you simply search x and delete it every time it comes up in the lists. For now, I'm simply going to make a skip list that stores numbers. I don't think there is anything in the STL that can assist me, so I will need to create a class List that holds an integer value and has member functions, search, delete, and insert. The problem I'm having is dealing with links. I'm pretty sure I could create a class to handle the "horizontal" links with a pointer to the previous element and the element in front, but I'm not sure how to deal with the "vertical" links (point to corresponding element in other list?) If any of my logic is flawed please tell me, but my main questions are: How to deal with vertical links and whether my link idea is correct Now that I read my class List idea I'm thinking that a List should hold a vector of integers rather than a single integer. In fact I'm pretty positive, but would just like some validation. I'm assuming the coin flip would simply call int function where rand()%2 returns a value of 0 or 1 and if it's 0 then a the value "levels up" and if it's 0 then the insert is over. Is this incorrect? How to store a value similar to -infinite? Edit: I've started writing some code and am considering how to handle the List constructor....I'm guessing that on its construction, the "-infinite" value should be stored in the vectorname[0] element and I can just call insert on it after its creation to put the x in the appropriate place.

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• how to insert into database from stored procedure in log4net?

  - by Samreen

  I have to log thread context properties like this: string logFilePath = AppDomain.CurrentDomain.BaseDirectory + "log4netconfig.xml"; FileInfo finfo = new FileInfo(logFilePath); log4net.Config.XmlConfigurator.ConfigureAndWatch(finfo); ILog logger = LogManager.GetLogger("Exception.Logging"); log4net.ThreadContext.Properties["MESSAGE"] = exception.Message; log4net.ThreadContext.Properties["MODULE"] = "module1"; log4net.ThreadContext.Properties["COMPONENT"] = "component1"; logger.Debug("test"); and the configuration file is: <configuration> <configSections> <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler,Log4net"/> </configSections> <log4net> <logger name="Exception.Logging" level="Debug"> <appender-ref ref="AdoNetAppender"/> </logger> <appender name="AdoNetAppender" type="log4net.Appender.AdoNetAppender"> <connectionString value="Data Source=xe;User ID=test;Password=test;" /> <connectionType value="System.Data.OracleClient.OracleConnection, System.Data.OracleClient, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /> <bufferSize value="10000"/> <commandText value="Log_Exception_Pkg.Insert_Log" /> <commandType value="StoredProcedure" /> <parameter> <parameterName value="@p_Error_Message" /> <dbType value="String" /> <size value="255" /> <layout type="log4net.Layout.PatternLayout"> <conversionPattern value="%property{MESSAGE}"/> </layout> </parameter> <parameter> <parameterName value="@p_Module" /> <dbType value="String" /> <size value="225" /> <layout type="log4net.Layout.PatternLayout"> <conversionPattern value="%property{MODULE}"/> </layout> </parameter> <parameter> <parameterName value="@p_Component" /> <dbType value="String" /> <size value="225" /> <layout type="log4net.Layout.PatternLayout"> <conversionPattern value="%property{COMPONENT}"/> </layout> </parameter> </appender> </log4net> </configuration> But its not inserting them in the database. How can I get that to work?

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• What to Expect in Rails 4

  - by mikhailov

  Rails 4 is nearly there, we should be ready before it released. Most developers are trying hard to keep their application on the edge. Must see resources: 1) @sikachu talk: What to Expect in Rails 4.0 - YouTube 2) Rails Guides release notes: http://edgeguides.rubyonrails.org/4_0_release_notes.html There is a mix of all major changes down here: ActionMailer changes excerpt: Asynchronously send messages via the Rails Raise an ActionView::MissingTemplate exception when no implicit template could be found ActionPack changes excerpt Added controller-level etag additions that will be part of the action etag computation Add automatic template digests to all CacheHelper#cache calls (originally spiked in the cache_digests plugin) Add Routing Concerns to declare common routes that can be reused inside others resources and routes Added ActionController::Live. Mix it in to your controller and you can stream data to the client live truncate now always returns an escaped HTML-safe string. The option :escape can be used as false to not escape the result Added ActionDispatch::SSL middleware that when included force all the requests to be under HTTPS protocol ActiveModel changes excerpt AM::Validation#validates ability to pass custom exception to :strict option Changed `AM::Serializers::JSON.include_root_in_json' default value to false. Now, AM Serializers and AR objects have the same default behaviour Added ActiveModel::Model, a mixin to make Ruby objects work with AP out of box Trim down Active Model API by removing valid? and errors.full_messages ActiveRecord changes excerpt Use native mysqldump command instead of structure_dump method when dumping the database structure to a sql file. Attribute predicate methods, such as article.title?, will now raise ActiveModel::MissingAttributeError if the attribute being queried for truthiness was not read from the database, instead of just returning false ActiveRecord::SessionStore has been extracted from Active Record as activerecord-session_store gem. Please read the README.md file on the gem for the usage Fix reset_counters when there are multiple belongs_to association with the same foreign key and one of them have a counter cache Raise ArgumentError if list of attributes to change is empty in update_all Add Relation#load. This method explicitly loads the records and then returns self Deprecated most of the 'dynamic finder' methods. All dynamic methods except for find_by_... and find_by_...! are deprecated Added ability to ActiveRecord::Relation#from to accept other ActiveRecord::Relation objects Remove IdentityMap ActiveSupport changes excerpt ERB::Util.html_escape now escapes single quotes ActiveSupport::Callbacks: deprecate monkey patch of object callbacks Replace deprecated memcache-client gem with dalli in ActiveSupport::Cache::MemCacheStore Object#try will now return nil instead of raise a NoMethodError if the receiving object does not implement the method, but you can still get the old behavior by using the new Object#try! Object#try can't call private methods Add ActiveSupport::Deprecations.behavior = :silence to completely ignore Rails runtime deprecations What are the most important changes for you?

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• WPF: Binding to ListBoxItem.IsSelected doesn't work for off-screen items

  - by Qwertie

  In my program I have a set of view-model objects to represent items in a ListBox (multi-select is allowed). The viewmodel has an IsSelected property that I would like to bind to the ListBox so that selection state is managed in the viewmodel rather than in the listbox itself. However, apparently the ListBox doesn't maintain bindings for most of the off-screen items, so in general the IsSelected property is not synchronized correctly. Here is some code that demonstrates the problem. First XAML: <StackPanel> <StackPanel Orientation="Horizontal"> <TextBlock>Number of selected items: </TextBlock> <TextBlock Text="{Binding NumItemsSelected}"/> </StackPanel> <ListBox ItemsSource="{Binding Items}" Height="200" SelectionMode="Extended"> <ListBox.ItemContainerStyle> <Style TargetType="{x:Type ListBoxItem}"> <Setter Property="IsSelected" Value="{Binding IsSelected}"/> </Style> </ListBox.ItemContainerStyle> </ListBox> <Button Name="TestSelectAll" Click="TestSelectAll_Click">Select all</Button> </StackPanel> C# Select All handler: private void TestSelectAll_Click(object sender, RoutedEventArgs e) { foreach (var item in _dataContext.Items) item.IsSelected = true; } C# viewmodel: public class TestItem : NPCHelper { TestDataContext _c; string _text; public TestItem(TestDataContext c, string text) { _c = c; _text = text; } public override string ToString() { return _text; } bool _isSelected; public bool IsSelected { get { return _isSelected; } set { _isSelected = value; FirePropertyChanged("IsSelected"); _c.FirePropertyChanged("NumItemsSelected"); } } } public class TestDataContext : NPCHelper { public TestDataContext() { for (int i = 0; i < 200; i++) _items.Add(new TestItem(this, i.ToString())); } ObservableCollection<TestItem> _items = new ObservableCollection<TestItem>(); public ObservableCollection<TestItem> Items { get { return _items; } } public int NumItemsSelected { get { return _items.Where(it => it.IsSelected).Count(); } } } public class NPCHelper : INotifyPropertyChanged { public event PropertyChangedEventHandler PropertyChanged; public void FirePropertyChanged(string prop) { if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(prop)); } } Two separate problems can be observed. If you click the first item and then press Shift+End, all 200 items should be selected; however, the heading reports that only 21 items are selected. If you click "Select all" then all items are indeed selected. If you then click an item in the ListBox you would expect the other 199 items to be deselected, but this does not happen. Instead, only the items that are on the screen (and a few others) are deselected. All 199 items will not be deselected unless you first scroll through the list from beginning to end (and even then, oddly enough, it doesn't work if you perform scrolling with the little scroll box). My questions are: Can someone explain precisely why this occurs? Can I avoid or work around the problem?

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• RAD Visual Web Application Creator/ Builder/ Designer for PHP

  - by inhoue

  Hi all, I want to see if any of you know a (free and open source will be ideal) tool/ app that can help build a php web application very quickly without investing too much time on writing codes, preferring drag and drop/ point and click work-flow designer for logic design (see Agile from Outsystems below). Plus, visual designer for the business logic is great since it can help a developer visualize the logic better. There are a lot of GUI builders, form builders out there, but I am looking for one app for the entire web application development process. My goal is to find an application that a team of developers can use together and use the build-in code of the app as much as possible. E.g. the app will provide a modular just for handle user login or a shopping cart; a developer just need to drag and drop the modular to the logic designer and the code will be generated. This way the functionality will be in a module and code will always be standard across developers. So if a new developer get on-board, he will just need to use the system and get up and running quickly. To explain this better: there is a lot php frameworks, e.g. cakephp, CodeIgniter, etc which I can use to help coding, but still I need to create (code) the GUI, writing quite a bit of codes. I am looking for a tool/ app that is a little more high level than those frameworks. Here is 2 examples apps I found during my google search which they have visual logic designer and gui builder in one single app. Also a single click deployment (but I need it to be php apps or at least I can deploy the (php) code to a LAMP/ WAMP server): Wavemaker: for JAVA Agile from Outsystems: for JAVA or .net (This one is really good, with work-flow drag and drop logic designer!) Talend: it is just an ETL tool, but the concept is what I want to bring up. Drag and drop, point and click logic design. Custom code can be added if it is needed, but the drag and drop process already finished the structure and most of the coding of the web app one needs to build. I want to list Adobe Flex, but it is more like a GUI designer + IDE, not exactly what I want to describe here. The drag and drop/ work-flow logic designer is a key for the app. I could go for the CMS route by learning how to extend them, but it is not that flexible for me and is a long learning curve. Anybody came across this type of app before? Or any idea of how can I find those apps? I googled them for long time, I don't see any of them for php and just few (just 2) for Java. Thanks in advance!

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• approximating log10[x^k0 + k1]

  - by Yale Zhang

  Greetings. I'm trying to approximate the function Log10[x^k0 + k1], where .21 < k0 < 21, 0 < k1 < ~2000, and x is integer < 2^14. k0 & k1 are constant. For practical purposes, you can assume k0 = 2.12, k1 = 2660. The desired accuracy is 5*10^-4 relative error. This function is virtually identical to Log[x], except near 0, where it differs a lot. I already have came up with a SIMD implementation that is ~1.15x faster than a simple lookup table, but would like to improve it if possible, which I think is very hard due to lack of efficient instructions. My SIMD implementation uses 16bit fixed point arithmetic to evaluate a 3rd degree polynomial (I use least squares fit). The polynomial uses different coefficients for different input ranges. There are 8 ranges, and range i spans (64)2^i to (64)2^(i + 1). The rational behind this is the derivatives of Log[x] drop rapidly with x, meaning a polynomial will fit it more accurately since polynomials are an exact fit for functions that have a derivative of 0 beyond a certain order. SIMD table lookups are done very efficiently with a single _mm_shuffle_epi8(). I use SSE's float to int conversion to get the exponent and significand used for the fixed point approximation. I also software pipelined the loop to get ~1.25x speedup, so further code optimizations are probably unlikely. What I'm asking is if there's a more efficient approximation at a higher level? For example: Can this function be decomposed into functions with a limited domain like log2((2^x) * significand) = x + log2(significand) hence eliminating the need to deal with different ranges (table lookups). The main problem I think is adding the k1 term kills all those nice log properties that we know and love, making it not possible. Or is it? Iterative method? don't think so because the Newton method for log[x] is already a complicated expression Exploiting locality of neighboring pixels? - if the range of the 8 inputs fall in the same approximation range, then I can look up a single coefficient, instead of looking up separate coefficients for each element. Thus, I can use this as a fast common case, and use a slower, general code path when it isn't. But for my data, the range needs to be ~2000 before this property hold 70% of the time, which doesn't seem to make this method competitive. Please, give me some opinion, especially if you're an applied mathematician, even if you say it can't be done. Thanks.

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• jquery dynamic select doesn't submit values

  - by n00b0101

  I have a form that includes three select boxes. The first one is categories, and selecting a category from it will populate the variables multi-select box with values specific to the selected category. Selecting variables and then clicking "add selected" will populate the target select box will those variables. The problem is, print_r shows that the values in the target select box aren't passed upon submit, and I don't understand why... Below is the code, and help is really appreciated Here's the html markup: <select multiple="" id="categories" name="categories[]"> <option class="category" value="Income">Income</option> <option class="category" value="Gender">Gender</option> <option class="category" value="Age">Age</option> </select> //note that i'm only showing variables for a presumably select category <select multiple="multiple" id="variables" name="variables[]"> <option value="2">Less Than $15,000</option> <option value="3">$15,000 - $19,999</option> <option value="4">$20,000 - $29,999</option> <option value="5">$30,000 - $39,999</option> <option value="6">$40,000 - $49,999</option> <option value="11">$90,000 - $99,999</option> <option value="12">$100,000 - $124,999</option> <option value="13">$125,000 - $149,999</option> <option value="14">Greater than $149,999</option> </select> <select name="target[]" id="target" multiple="multiple" height="60"> </select> And here's the jquery code: $(function(){ var opts = {}, $cats = $("#categories"), $target = $("#target"), $vars = $("#variables"); $vars.find("option").each(function(){ var $opt = $(this), cat = this.className, value = this.value, label = $opt.text(); if(!opts[cat]) { opts[cat] = []; } opts[cat].push({label: label, value: value}); $opt.remove(); }); function update_variables(){ var cat = $cats.val(), new_opts = []; $vars.empty(); $.each(opts[cat], function(){ if( $target.find('[value=' + this.value + ']').length === 0 ){ new_opts.push(option(this.value, this.label)); } }); $vars.html(new_opts.join('')); } function option(value, label){ return "<option value='" + value + "'>" + label + "</option>"; } $("#add").click(function(e){ e.preventDefault(); $vars.find(':selected').appendTo($target).attr('selected',false); update_variables(); }); $("#remove").click(function(e){ e.preventDefault(); $target.find(':selected').remove(); update_variables(); }); $cats.change(function(){ update_variables(); }).change(); })

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• dynamic module creation

  - by intuited

  I'd like to dynamically create a module from a dictionary, and I'm wondering if adding an element to sys.modules is really the best way to do this. EG context = { a: 1, b: 2 } import types test_context_module = types.ModuleType('TestContext', 'Module created to provide a context for tests') test_context_module.__dict__.update(context) import sys sys.modules['TestContext'] = test_context_module My immediate goal in this regard is to be able to provide a context for timing test execution: import timeit timeit.Timer('a + b', 'from TestContext import *') It seems that there are other ways to do this, since the Timer constructor takes objects as well as strings. I'm still interested in learning how to do this though, since a) it has other potential applications; and b) I'm not sure exactly how to use objects with the Timer constructor; doing so may prove to be less appropriate than this approach in some circumstances. EDITS/REVELATIONS/PHOOEYS/EUREKAE: I've realized that the example code relating to running timing tests won't actually work, because import * only works at the module level, and the context in which that statement is executed is that of a function in the testit module. In other words, the globals dictionary used when executing that code is that of main, since that's where I was when I wrote the code in the interactive shell. So that rationale for figuring this out is a bit botched, but it's still a valid question. I've discovered that the code run in the first set of examples has the undesirable effect that the namespace in which the newly created module's code executes is that of the module in which it was declared, not its own module. This is like way weird, and could lead to all sorts of unexpected rattlesnakeic sketchiness. So I'm pretty sure that this is not how this sort of thing is meant to be done, if it is in fact something that the Guido doth shine upon. The similar-but-subtly-different case of dynamically loading a module from a file that is not in python's include path is quite easily accomplished using imp.load_source('NewModuleName', 'path/to/module/module_to_load.py'). This does load the module into sys.modules. However this doesn't really answer my question, because really, what if you're running python on an embedded platform with no filesystem? I'm battling a considerable case of information overload at the moment, so I could be mistaken, but there doesn't seem to be anything in the imp module that's capable of this. But the question, essentially, at this point is how to set the global (ie module) context for an object. Maybe I should ask that more specifically? And at a larger scope, how to get Python to do this while shoehorning objects into a given module?

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• how to develop a program to minimize errors in human transcription of hand written surveys

  - by Alex. S.

  I need to develop custom software to do surveys. Questions may be of multiple choice, or free text in a very few cases. I was asked to design a subsystem to check if there is any error in the manual data entry for the multiple choices part. We're trying to speed up the user data entry process and to minimize human input differences between digital forms and the original questionnaires. The surveys are filled with handwritten marks and text by human interviewers, so it's possible to find hard to read marks, or also the user could accidentally select a different value in some question, and we would like to avoid that. The software must include some automatic control to detect possible typing differences. Each answer of the multiple choice questions has the same probability of being selected. This question has two parts: The GUI. The most simple thing I have in mind is to implement the most usable design of the questions display: use of large and readable fonts and space generously the choices. Is there something else? For faster input, I would like to use drop down lists (favoring keyboard over mouse). Given the questions are grouped in sections, I would like to show the answers selected for the questions of that section, but this could slow down the process. Any other ideas? The error checking subsystem. What else can I do to minimize or to check human typos in the multiple choice questions? Is this a solvable problem? is there some statistical methodology to check values that were entered by the users are the same from the hand filled forms? For example, let's suppose the survey has 5 questions, and each has 4 options. Let's say I have n survey forms filled in paper by interviewers, and they're ready to be entered in the software, then how to minimize the accidental differences that can have the manual transcription of the n surveys, without having to double check everything in the 5 questions of the n surveys? My first suggestion is that at the end of the processing of all the hand filled forms, the software could choose some forms randomly to make a double check of the responses in a few instances, but on what criteria can I make this selection? This validation would be enough to cover everything in a significant way? The actual survey is nation level and it has 56 pages with over 200 questions in total, so it will be a lot of hand written pages by many people, and the intention is to reduce the likelihood of errors and to optimize speed in the data entry process. The surveys must filled in paper first, given the complications of taking laptops or handhelds with the interviewers.

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• iPhone App Crashes when merging managed object contexts

  - by DVG

  Short Version: Using two managed object contexts, and while the context is saving to the store the application bombs when I attempt to merge the two contexts and reload the table view. Long Version: Okay, so my application is set up as thus. 3 view controllers, all table views. Platforms View Controller - Games View Controller (Predicated upon platform selection) - Add Game View Controller I ran into a problem when Games View Controller was bombing when adding a new entry to the context, because the fetched results contorller wanted to update the view for something that didn't match the predicate. As a solution, I rebuilt the Add Controller to use a second NSManagedObject Context, called adding context, following the design pattern in the Core Data Books example. My Games List View Controller is a delegate for the add controller, to handle all the saving, so my addButtonPressed method looks like this - (IBAction) addButtonPressed: (id) sender { AddGameTableViewController *addGameVC = [[AddGameTableViewController alloc] initWithNibName:@"AddGameTableViewController" bundle:nil]; NSManagedObjectContext *aAddingContext = [[NSManagedObjectContext alloc] init]; self.addingContext = aAddingContext; [aAddingContext release]; [addingContext setPersistentStoreCoordinator:[[gameResultsController managedObjectContext] persistentStoreCoordinator]]; addGameVC.context = addingContext; addGameVC.delegate = self; addGameVC.newGame = (Game *)[NSEntityDescription insertNewObjectForEntityForName:@"Game" inManagedObjectContext:addingContext]; UINavigationController *addNavCon = [[UINavigationController alloc] initWithRootViewController:addGameVC]; [self presentModalViewController:addNavCon animated:YES]; [addGameVC release]; [addNavCon release]; } There is also a delegate method which handles the saving. This all works swimmingly. The issue is getting the table view controller in the GameListViewController to update itself. Per the example, an observer is added to watch for the second context to be saved, and then to merge the addingContext with the primary one. So I have: - (void)addViewController:(AddGameTableViewController *)controller didFinishWithSave:(BOOL)save { if (save) { NSNotificationCenter *dnc = [NSNotificationCenter defaultCenter]; [dnc addObserver:self selector:@selector(addControllerContextDidSave:) name:NSManagedObjectContextDidSaveNotification object:addingContext]; //snip! Context Save Code [dnc removeObserver:self name:NSManagedObjectContextDidSaveNotification object:addingContext]; } self.addingContext = nil; [self dismissModalViewControllerAnimated:YES]; } - (void)addControllerContextDidSave:(NSNotification*)saveNotification { NSManagedObjectContext *myContext = [gameResultsController managedObjectContext]; [myContext mergeChangesFromContextDidSaveNotification:saveNotification]; } So now, what happens is after save is pressed, the application hangs for a moment and then crashes. The save is processed, as the new game is present when I relaunch the application, and the application seems to be flowing as appropriate, but it bombs out for reasons that are beyond my understanding. NSLog of the saveNotification spits out this: NSConcreteNotification 0x3b557f0 {name = NSManagingContextDidSaveChangesNotification; object = <NSManagedObjectContext: 0x3b4bb90>; userInfo = { inserted = {( <Game: 0x3b4f510> (entity: Game; id: 0x3b614e0 <x-coredata://13168366-B8E7-41C8-B384-BAF14A5E08D9/Game/p2> ; data: { name = "Final Fantasy XIII"; platform = 0x3b66910 <x-coredata://13168366-B8E7-41C8-B384-BAF14A5E08D9/Platform/p20>; }) )}; updated = {( <Platform: 0x3b67650> (entity: Platform; id: 0x3b66910 <x-coredata://13168366-B8E7-41C8-B384-BAF14A5E08D9/Platform/p20> ; data: { games = ( 0x3b614e0 <x-coredata://13168366-B8E7-41C8-B384-BAF14A5E08D9/Game/p2>, 0x603a530 <x-coredata://13168366-B8E7-41C8-B384-BAF14A5E08D9/Game/p1> ); name = "Xbox 360"; }) )}; }} I've tried both a simple [self.tableView reloadData]; and the more complicated multi-method table updating structure in the Core Data Books example. Both produce the same result.

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• NSNotifications vs delegate for multiple instances of same protocol

  - by Brent Traut

  I could use some architectural advice. I've run into the following problem a few times now and I've never found a truly elegant way to solve it. The issue, described at the highest level possible:I have a parent class that would like to act as the delegate for multiple children (all using the same protocol), but when the children call methods on the parent, the parent no longer knows which child is making the call. I would like to use loose coupling (delegates/protocols or notifications) rather than direct calls. I don't need multiple handlers, so notifications seem like they might be overkill. To illustrate the problem, let me try a super-simplified example: I start with a parent view controller (and corresponding view). I create three child views and insert each of them into the parent view. I would like the parent view controller to be notified whenever the user touches one of the children. There are a few options to notify the parent: Define a protocol. The parent implements the protocol and sets itself as the delegate to each of the children. When the user touches a child view, its view controller calls its delegate (the parent). In this case, the parent is notified that a view is touched, but it doesn't know which one. Not good enough. Same as #1, but define the methods in the protocol to also pass some sort of identifier. When the child tells its delegate that it was touched, it also passes a pointer to itself. This way, the parent know exactly which view was touched. It just seems really strange for an object to pass a reference to itself. Use NSNotifications. The parent defines a separate method for each of the three children and then subscribes to the "viewWasTouched" notification for each of the three children as the notification sender. The children don't need to attach themselves to the user dictionary, but they do need to send the notification with a pointer to themselves as the scope. Same as #4, but rather than using separate methods, the parent could just use one with a switch case or other branching along with the notification's sender to determine which path to take. Create multiple man-in-the-middle classes that act as the delegates to the child views and then call methods on the parent either with a pointer to the child or with some other differentiating factor. This approach doesn't seem scalable. Are any of these approaches considered best practice? I can't say for sure, but it feels like I'm missing something more obvious/elegant.

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• Killing Mysql processes staying in sleep command.

  - by Shino88

  Hey I am connecting a MYSQL database through hibernate and i seem to have processes that are not being killed after they are finished in the session. I have called flush and close on each session but when i check the server the last processes are still there with a sleep command. This is a new problem which i am having and was not the case yesterday. Is there any way i can ensure the killng of theses processes when i am done with a session. Below is an example of one of my classes. public JSONObject check() { //creates a new session needed to add elements to a database Session session = null; //holds the result of the check in the database JSONObject check = new JSONObject(); try{ //creates a new session needed to add elements to a database SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory(); session = sessionFactory.openSession(); if (justusername){ //query created to select a username from user table String hquery = "Select username from User user Where username = ? "; //query created Query query = session.createQuery(hquery); //sets the username of the query the values JSONObject contents query.setString(0, username); // executes query and adds username string variable String user = (String) query.uniqueResult(); //checks to see if result is found (null if not found) if (user == null) { //adds false to Jobject if not found check.put("indatabase", "false"); } else { check.put("indatabase", "true"); } //adds check to Jobject to say just to check username check.put("justusername", true); } else { //query created to select a username and password from user table String hquery = "Select username from User user Where username = :user and password = :pass "; Query query = session.createQuery(hquery); query.setString("user", username); query.setString("pass", password); String user = (String) query.uniqueResult(); if(user ==null) { check.put("indatabase", false); } else { check.put("indatabase", true); } check.put("justusername", false); } }catch(Exception e){ System.out.println(e.getMessage()); //logg.log(Level.WARNING, " Exception", e.getMessage()); }finally{ // Actual contact insertion will happen at this step session.flush(); session.close(); } //returns Jobject return check; }

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• How to reduce virtual memory by optimising my PHP code?

  - by iCeR

  My current code (see below) uses 147MB of virtual memory! My provider has allocated 100MB by default and the process is killed once run, causing an internal error. The code is utilising curl multi and must be able to loop with more than 150 iterations whilst still minimizing the virtual memory. The code below is only set at 150 iterations and still causes the internal server error. At 90 iterations the issue does not occur. How can I adjust my code to lower the resource use / virtual memory? Thanks! <?php function udate($format, $utimestamp = null) { if ($utimestamp === null) $utimestamp = microtime(true); $timestamp = floor($utimestamp); $milliseconds = round(($utimestamp - $timestamp) * 1000); return date(preg_replace('`(?<!\\\\)u`', $milliseconds, $format), $timestamp); } $url = 'https://www.testdomain.com/'; $curl_arr = array(); $master = curl_multi_init(); for($i=0; $i<150; $i++) { $curl_arr[$i] = curl_init(); curl_setopt($curl_arr[$i], CURLOPT_URL, $url); curl_setopt($curl_arr[$i], CURLOPT_RETURNTRANSFER, 1); curl_setopt($curl_arr[$i], CURLOPT_SSL_VERIFYHOST, FALSE); curl_setopt($curl_arr[$i], CURLOPT_SSL_VERIFYPEER, FALSE); curl_multi_add_handle($master, $curl_arr[$i]); } do { curl_multi_exec($master,$running); } while($running > 0); for($i=0; $i<150; $i++) { $results = curl_multi_getcontent ($curl_arr[$i]); $results = explode("<br>", $results); echo $results[0]; echo "<br>"; echo $results[1]; echo "<br>"; echo udate('H:i:s:u'); echo "<br><br>"; usleep(100000); } ?> Processor Information Total processors: 8 Processor #1 Vendor GenuineIntel Name Intel(R) Xeon(R) CPU E5405 @ 2.00GHz Speed 1995.120 MHz Cache 6144 KB Processor #2 Vendor GenuineIntel Name Intel(R) Xeon(R) CPU E5405 @ 2.00GHz Speed 1995.120 MHz Cache 6144 KB Processor #3 Vendor GenuineIntel Name Intel(R) Xeon(R) CPU E5405 @ 2.00GHz Speed 1995.120 MHz Cache 6144 KB Processor #4 Vendor GenuineIntel Name Intel(R) Xeon(R) CPU E5405 @ 2.00GHz Speed 1995.120 MHz Cache 6144 KB Processor #5 Vendor GenuineIntel Name Intel(R) Xeon(R) CPU E5405 @ 2.00GHz Speed 1995.120 MHz Cache 6144 KB Processor #6 Vendor GenuineIntel Name Intel(R) Xeon(R) CPU E5405 @ 2.00GHz Speed 1995.120 MHz Cache 6144 KB Processor #7 Vendor GenuineIntel Name Intel(R) Xeon(R) CPU E5405 @ 2.00GHz Speed 1995.120 MHz Cache 6144 KB Processor #8 Vendor GenuineIntel Name Intel(R) Xeon(R) CPU E5405 @ 2.00GHz Speed 1995.120 MHz Cache 6144 KB Memory Information Memory for crash kernel (0x0 to 0x0) notwithin permissible range Memory: 8302344k/9175040k available (2176k kernel code, 80272k reserved, 901k data, 228k init, 7466304k highmem) System Information Linux server3.server.com 2.6.18-194.17.1.el5PAE #1 SMP Wed Sep 29 13:31:51 EDT 2010 i686 i686 i386 GNU/Linux Physical Disks SCSI device sda: 1952448512 512-byte hdwr sectors (999654 MB) sda: Write Protect is off sda: Mode Sense: 03 00 00 08 SCSI device sda: drive cache: write back SCSI device sda: 1952448512 512-byte hdwr sectors (999654 MB) sda: Write Protect is off sda: Mode Sense: 03 00 00 08 SCSI device sda: drive cache: write back sd 0:1:0:0: Attached scsi disk sda sd 4:0:0:0: Attached scsi removable disk sdb sd 0:1:0:0: Attached scsi generic sg4 type 0 sd 4:0:0:0: Attached scsi generic sg7 type 0 Current Memory Usage total used free shared buffers cached Mem: 8306672 7847384 459288 0 487912 6444548 -/+ buffers/cache: 914924 7391748 Swap: 4095992 496 4095496 Total: 12402664 7847880 4554784 Current Disk Usage Filesystem Size Used Avail Use% Mounted on /dev/mapper/VolGroup00-LogVol00 898G 307G 546G 36% / /dev/sda1 99M 19M 76M 20% /boot none 4.0G 0 4.0G 0% /dev/shm /var/tmpMnt 4.0G 1.8G 2.0G 48% /tmp

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• Is "Systems Designer" the job title that best describes what I do? [closed]

  - by ivo-rossi

  After having worked as Java developer for almost 3 years in the same company that I currently work at, I moved to a new position associated with the development of the same application. I’m in this new position for more than 1 year now. My official job title is Systems Designer, but I’m not sure this is a title that expresses well what I do. So my question here is what would be the most appropriate job title for me? I see this question as important for my career development. After all, I should be able to explain in one word what I do. And it’s no longer “Java Developer”. Well, in more than one word, this is what I do: The business analysts gather requirements / business problems to be solved with the clients and then discuss these requirements with me. Given the requirements, I design the high level solutions to be implemented in our system (e.g. a new screen on the client application, modifications to existing reports, extension to the XML export format of some objects, etc). I base my decision on the current capabilities of the system, the overall impact that the solutions would have on the system and the estimated effort to implement them (as I was a developer of this same application for almost 3 years before I moved to this position, I’m confident in my estimates). The solutions are discussed iteratively with the business analysts until we agree that they are good. The outcome of this analysis is what we call the “requirements design” document, which is written by me, shared with clients for approval and then also with the team that is going to implement the solutions and test them. Note that there are a few problems that I need to find a solution for that are non-functional. If the users are unhappy with the performance of a certain tool, I will investigate what can be done to speed it up. I will do some research – often based in the Java code itself - to identify possibilities of optimizations. But in this new position I no longer code, the main outcome of my work is really the “requirements design”. Is “Systems Designer” really the most appropriate job title?

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• JQuery $.ajax doesn't return anything, but only in Google Chrome!?

  - by Shawson

  Hi All, I'm hoping someone can help me with this as I'm at a loss. I'm trying to simply load a plain text file into a page at runtime using jquery- everything works fine in IE8 (8.0.7600.16385), Firefox 3.6.3, however in Google Chrome 5.0.375.55 the "data" comes back as nothing- i get an empty alert box. This is the code i'm using; <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Animation Test</title> <script type="text/javascript" language="javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script> <script type="text/javascript" language="javascript"> $(document).ready(function () { $.ajax({ url: 'level1.txt', success: function (data) { alert(data); }, async: true, type: 'GET' }); }); </script> </head> <body> <canvas id="canvas" width="640" height="480"> Unsupported Browser </canvas> </body> </html> The file I'm loading in is a plain text file containing this; Central Cavern 100 O.........1.C....C...........1.O O................1.............O O..............................O O..............................O O......................B1..B...O O=============~~~~=~~~~========O O.............................1O O===...........................O O............A..OOO.B..........O O====...<<<<<<<<<<<<<<<<<<<<...O O............................==O O..............................O O..........B........OOO.....===O O....===============...........O O%............................XO O==============================O (Yes- it's the first level from Manic Miner! I'm making a javascript version using the html5 canvas to get my head around using it.) I'm at a total loss- it can't be the code because it runs in the other 2 browsers- is there an issue with jquery and this version of Chrome? Thanks for reading!! Shaw.

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• How to implement a caching model without violating MVC pattern?

  - by RPM1984

  Hi Guys, I have an ASP.NET MVC 3 (Razor) Web Application, with a particular page which is highly database intensive, and user experience is of the upmost priority. Thus, i am introducing caching on this particular page. I'm trying to figure out a way to implement this caching pattern whilst keeping my controller thin, like it currently is without caching: public PartialViewResult GetLocationStuff(SearchPreferences searchPreferences) { var results = _locationService.FindStuffByCriteria(searchPreferences); return PartialView("SearchResults", results); } As you can see, the controller is very thin, as it should be. It doesn't care about how/where it is getting it's info from - that is the job of the service. A couple of notes on the flow of control: Controllers get DI'ed a particular Service, depending on it's area. In this example, this controller get's a LocationService Services call through to an IQueryable<T> Repository and materialize results into T or ICollection<T>. How i want to implement caching: I can't use Output Caching - for a few reasons. First of all, this action method is invoked from the client-side (jQuery/AJAX), via [HttpPost], which according to HTTP standards should not be cached as a request. Secondly, i don't want to cache purely based on the HTTP request arguments - the cache logic is a lot more complicated than that - there is actually two-level caching going on. As i hint to above, i need to use regular data-caching, e.g Cache["somekey"] = someObj;. I don't want to implement a generic caching mechanism where all calls via the service go through the cache first - i only want caching on this particular action method. First thought's would tell me to create another service (which inherits LocationService), and provide the caching workflow there (check cache first, if not there call db, add to cache, return result). That has two problems: The services are basic Class Libraries - no references to anything extra. I would need to add a reference to System.Web here. I would have to access the HTTP Context outside of the web application, which is considered bad practice, not only for testability, but in general - right? I also thought about using the Models folder in the Web Application (which i currently use only for ViewModels), but having a cache service in a models folder just doesn't sound right. So - any ideas? Is there a MVC-specific thing (like Action Filter's, for example) i can use here? General advice/tips would be greatly appreciated.

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• Hibernate: update on parent-child relationship causes duplicate children

  - by TimmyJ

  I have a parent child relationship in which the parent has a collection of children (a set to be specific). The child collection is setup with cascade="all-delete-orphan". When I initially save the parent element everything works as expected. However, when I update the parent and save again, all the children are re-saved. This behavior leads me to believe that the parent is losing its reference to the collection of children, and therefore when persisting all the children are re-saved. It seems the only way to fix this is to not use the setter method of this child collection, but unfortunately this setter is called implicitly in my application (Spring MVC is used to bind a multi-select form element to this collection, and the setter is called by spring on the form submission). Overwriting this setter to not lose the reference (ie, do a colleciton.clear() and collection.addAll(newCollection) rather than collection = newCollection) is apparently a hibernate no-no, as is pointed out here: https://forum.hibernate.org/viewtopic.php?t=956859 Does anyone know how to circumvent this problem? I've posted some of my code below. The parent hibernate configuration: <hibernate-mapping package="org.fstrf.masterpk.domain"> <class name="ReportCriteriaBean" table="masterPkReportCriteria"> <id name="id" column="id"> <generator class="org.hibernate.id.IncrementGenerator" /> </id> <set name="treatmentArms" table="masterPkTreatmentArms" sort="org.fstrf.masterpk.domain.RxCodeComparator" lazy="false" cascade="all-delete-orphan" inverse="true"> <key column="runid"/> <one-to-many class="TreatmentArm"/> </set> </class> </hibernate-mapping> The parent object: public class ReportCriteriaBean{ private Integer id; private Set<TreatmentArm> treatmentArms; public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public Set<TreatmentArm> getTreatmentArms() { return treatmentArms; } public void setTreatmentArms(Set<TreatmentArm> treatmentArms) { this.treatmentArms = treatmentArms; if(this.treatmentArms != null){ for(TreatmentArm treatmentArm : this.treatmentArms){ treatmentArm.setReportCriteriaBean(this); } } } The child hibernate configuration: <hibernate-mapping package="org.fstrf.masterpk.domain"> <class name="TreatmentArm" table="masterPkTreatmentArms"> <id name="id" column="id"> <generator class="org.hibernate.id.IncrementGenerator" /> </id> <many-to-one name="reportCriteriaBean" class="ReportCriteriaBean" column="runId" not-null="true" /> <property name="rxCode" column="rxCode" not-null="true"/> </class> </hibernate-mapping> The child object: public class TreatmentArm { private Integer id; private ReportCriteriaBean reportCriteriaBean; private String rxCode; public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public ReportCriteriaBean getReportCriteriaBean() { return reportCriteriaBean; } public void setReportCriteriaBean(ReportCriteriaBean reportCriteriaBean) { this.reportCriteriaBean = reportCriteriaBean; } public String getRxCode() { return rxCode; } public void setRxCode(String rxCode) { this.rxCode = rxCode; } }

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• Need help with regex parsing (in perl)

  - by Charlie

  Hi all, need some help parsing an html file in perl. I used the LWP module to retrieve a webpage into $_ with $/ undefined so there are no newline issues. Then I'm trying to find all strings matching a pattern. How do I do that? I know how to find 1 instance of it, but how do I match all instances? and what data structure would the results go to? a multi dimensional array? my text (excerpt) looks like the following: <TR> <TD BGCOLOR=EEEEEE><A HREF="/program.cgi?pid=1233"><FONT FACE="ARIAL,HELVETICA,SANS-SERIF" SIZE=2>Title 1</A></FONT></TD> <TD BGCOLOR=EEEEEE nowrap><FONT FACE="ARIAL,HELVETICA" SIZE=2>Jun 27 2010 3:00PM</FONT></TD> <TD BGCOLOR=EEEEEE>&nbsp;</TD> </TR> <TR><TD BGCOLOR=EEEEEE COLSPAN=3><IMG SRC="http://images.domain.com/images/spacer.gif" WIDTH=1 HEIGHT=2><BR></TD></TR> <TR><TD COLSPAN=3 BGCOLOR=999999><IMG SRC="http://images.domain.com/images/spacer.gif" HEIGHT=1 WIDTH=1></TD></TR> <TR><TD COLSPAN=3 ><IMG SRC="http://images.domain.com/images/spacer.gif" WIDTH=1 HEIGHT=2><BR></TD></TR> <TR> <TD><A HREF="/program.cgi?pid=1234"><FONT FACE="ARIAL,HELVETICA,SANS-SERIF" SIZE=2>Title 2</A></FONT></TD> <TD nowrap><FONT FACE="ARIAL,HELVETICA" SIZE=2>Jun 29 2010 7:00PM</FONT></TD> <TD>&nbsp;</TD> </TR> <TR><TD COLSPAN=3><IMG SRC="http://images.domain.com/images/spacer.gif" WIDTH=1 HEIGHT=2><BR></TD></TR> <TR><TD COLSPAN=3 BGCOLOR=999999><IMG SRC="http://images.domain.com/images/spacer.gif" HEIGHT=1 WIDTH=1></TD></TR> <TR><TD COLSPAN=3 BGCOLOR=EEEEEE><IMG SRC="http://images.domain.com/images/spacer.gif" WIDTH=1 HEIGHT=2><BR></TD></TR> <TR> <TD BGCOLOR=EEEEEE><A HREF="/program.cgi?pid=1235"><FONT FACE="ARIAL,HELVETICA,SANS-SERIF" SIZE=2>Title 3</A></FONT></TD> <TD BGCOLOR=EEEEEE nowrap><FONT FACE="ARIAL,HELVETICA" SIZE=2>Jul 3 2010 7:00PM</FONT></TD> <TD BGCOLOR=EEEEEE>&nbsp;</TD> </TR> I want to get the following into an array (or any structure): { ["/program.cgi?pdi=1233", "Title 1"], ["/program.cgi?pdi=1234", "Title 2"], ["/program.cgi?pdi=1235", "Title 3"] } Thanks

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• ADO program to list members of a large group.

  - by AlexGomez

  Hi everyone, I'm attempting to list all the members in a Active Directory group using ADO. The problem I have is that many of these groups have over 1500 members and ADSI cannot handle more than 1500 items in a multi-valued attribute. Fortunately I came across Richard Muller's wonderful VBScript that handles more than 1500 members at http://www.rlmueller.net/DocumentLargeGroup.htm I modified his code as shown below so that I can list ALL the groups and its memberships in a certain OU. However, I'm keeping getting the exception shown below: "ADODB.Recordset: Item cannot be found in the collection corresponding to the requested name or ordinal." My program appears to get stuck at: strPath = adoRecordset.Fields("ADsPath").Value Set objGroup = GetObject(strPath) All I am doing above is issuing the query to get back a recordset consisting of the ADsPath for each group in the OU. It then walks through the recordset and grabs the ADsPath for the first group and store its in a variable named strPath; we then use the value of that variable to bind to the group account for that group. It really should work! Any idea why the code below doesn't work for me? Any pointers will be great appreciated. Thanks. Option Explicit Dim objRootDSE, strDNSDomain, adoCommand Dim adoConnection, strBase, strAttributes Dim strFilter, strQuery, adoRecordset Dim strDN, intCount, blnLast, intLowRange Dim intHighRange, intRangeStep, objField Dim objGroup, objMember, strName ' Determine DNS domain name. Set objRootDSE = GetObject("LDAP://RootDSE") 'strDNSDomain = objRootDSE.Get("DefaultNamingContext") strDNSDomain = "XXXXXXXX" ' Use ADO to search Active Directory. Set adoCommand = CreateObject("ADODB.Command") Set adoConnection = CreateObject("ADODB.Connection") adoConnection.Provider = "ADsDSOObject" adoConnection.Open = "Active Directory Provider" adoCommand.ActiveConnection = adoConnection adoCommand.Properties("Page Size") = 100 adoCommand.Properties("Timeout") = 30 adoCommand.Properties("Cache Results") = False ' Specify base of search. strBase = "<LDAP://" & strDNSDomain & ">" ' Specify the attribute values to retrieve. strAttributes = "member" ' Filter on objects of class "group" strFilter = "(&(objectClass=group)(samAccountName=*))" ' Enumerate direct group members. ' Use range limits to handle more than 1000/1500 members. ' Setup to retrieve 1000 members at a time. blnLast = False intRangeStep = 999 intLowRange = 0 IntHighRange = intLowRange + intRangeStep Do While True If (blnLast = True) Then ' If last query, retrieve remaining members. strQuery = strBase & ";" & strFilter & ";" _ & strAttributes & ";range=" & intLowRange _ & "-*;subtree" Else ' If not last query, retrieve 1000 members. strQuery = strBase & ";" & strFilter & ";" _ & strAttributes & ";range=" & intLowRange & "-" _ & intHighRange & ";subtree" End If adoCommand.CommandText = strQuery Set adoRecordset = adoCommand.Execute adoRecordset.MoveFirst intCount = 0 Do Until adoRecordset.EOF strPath = adoRecordset.Fields("ADsPath").Value Set objGroup = GetObject(strPath) For Each objField In adoRecordset.Fields If (VarType(objField) = (vbArray + vbVariant)) _ Then For Each strDN In objField.Value ' Escape any forward slash characters, "/", with the backslash ' escape character. All other characters that should be escaped are. strDN = Replace(strDN, "/", "\/") ' Check dictionary object for duplicates. 'If (objGroupList.Exists(strDN) = False) Then ' Add to dictionary object. 'objGroupList.Add strDN, True ' Bind to each group member, to find member's samAccountName Set objMember = GetObject("LDAP://" & strDN) ' Output group cn, group samaAccountName and group member's samAccountName. Wscript.Echo objMember.samAccountName intCount = intCount + 1 'End if Next End If Next adoRecordset.MoveNext Loop adoRecordset.Close ' If this is the last query, exit the Do While loop. If (blnLast = True) Then Exit Do End If ' If the previous query returned no members, then the previous ' query for the next 1000 members failed. Perform one more ' query to retrieve remaining members (less than 1000). If (intCount = 0) Then blnLast = True Else ' Setup to retrieve next 1000 members. intLowRange = intHighRange + 1 intHighRange = intLowRange + intRangeStep End If Loop

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• Getting instance crashes on IntelliJ IDEA with scala plugin.

  - by egervari

  I am building a scala web project using scala test, lift, jpa, hibernate, mercurial plugin, etc. I am getting instant crashes, where the ide just bombs, the window shuts down, and it gives no error messages whatsoever when I am doing any amount of copy/pasting of code. This started happening once my project got to about 100 unit tests. This problem is incredibly annoying, because when the crash happens, 30-60 seconds of activity is not saved. Even IDEA will forget which files were last opened and will forget where the cursor was, which makes it really hard to continue where you left off after the crash. A lot can happen in 60 seconds! Now, I've given up, because it seems like all sorts of things cause the IntelliJ IDEA to crash over and over. For example, if I were to copy and paste this code, to write a similar test for another collection type, it would crash shortly after: it should "cascade save and delete status messages" in { val statusMessage = new StatusMessage("message") var user = userDao.find(1).get user.addToStatusMessages(statusMessage) userDao.save(user) statusMessage.isPersistent should be (true) userDao.delete(user) statusMessageDao.find(statusMessage.id) should equal (None) } There is nothing special about this piece of code. It's code that is working just fine. However, IDEA bombs shortly after I paste something like this. For example, I might change StatusMessage to the new class I want to test cascading on... and then have to import that class into the test... and BOOM... it crashed. On windows 7, the IDEA window literally just minimizes and crashes with no warning. The next time I startup IDEA, it has no memory of what happened. Now, I've had this problem before. I posted it way back on IDEA's YouTrack. I was told to invalidate my caches. That never fixed it then, and it's not fixing it now. Please help. This error is fairly random, but it's happening constantly now. I could program for hours and not see it before... and the fact that my work just gets destroyed and I can't remember what I did during the last minute causes me to swear at my monitor at a db level higher than my stereo can go.

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• Exporting classes containing std:: objects (vector, map, etc) from a dll

  - by RnR

  I'm trying to export classes from a DLL that contain objects such as std::vectors and std::stings - the whole class is declared as dll export through: class DLL_EXPORT FontManager { The problem is that for members of the complex types I get this warning: warning C4251: 'FontManager::m__fonts' : class 'std::map<_Kty,_Ty' needs to have dll-interface to be used by clients of class 'FontManager' with [ _Kty=std::string, _Ty=tFontInfoRef ] I'm able to remove some of the warnings by putting the following forward class declaration before them even though I'm not changing the type of the member variables themselves: template class DLL_EXPORT std::allocator<tCharGlyphProviderRef>; template class DLL_EXPORT std::vector<tCharGlyphProviderRef,std::allocator<tCharGlyphProviderRef> >; std::vector<tCharGlyphProviderRef> m_glyphProviders; Looks like the forward declaration "injects" the DLL_EXPORT for when the member is compiled but is it safe? Does it realy change anything when the client compiles this header and uses the std container on his side? Will it make all future uses of such a container DLL_EXPORT (and possibly not inline?)? And does it really solve the problem that the warning tries to warn about? Is this warning anything I should be worried about or would it be best to disable it in the scope of these constructs? The clients and the dll will always be built using the same set of libraries and compilers and those are header only classes... I'm using Visual Studio 2003 with the standard STD library. ---- Update ---- I'd like to target you more though as I see the answers are general and here we're talking about std containers and types (such as std::string) - maybe the question really is: Can we disable the warning for standard containers and types available to both the client and the dll through the same library headers and treat them just as we'd treat an int or any other built-in type? (It does seem to work correctly on my side.) If so would should be the conditions under which we can do this? Or should maybe using such containers be prohibited or at least ultra care taken to make sure no assignment operators, copy constructors etc will get inlined into the dll client? In general I'd like to know if you feel designing a dll interface having such objects (and for example using them to return stuff to the client as return value types) is a good idea or not and why - I'd like to have a "high level" interface to this functionality... maybe the best solution is what Neil Butterworth suggested - creating a static library?

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• What does a WinForm application need to be designed for usability, and be robust, clean, and profess

  - by msorens

  One of the principal problems impeding productivity in software implementation is the classic conundrum of “reinventing the wheel”. Of late I am a .NET developer and even the wonderful wizardry of .NET and Visual Studio covers only a portion of this challenging issue. Below I present my initial thoughts both on what is available and what should be available from .NET on a WinForm, focusing on good usability. That is, aspects of an application exposed to the user and making the user experience easier and/or better. (I do include a couple items not visible to the user because I feel strongly about them, such as diagnostics.) I invite you to contribute to these lists. LIST A: Components provided by .NET These are substantially complete components provided by .NET, i.e. those requiring at most trivial coding to use. “About” dialog -- add it with a couple clicks then customize. Persist settings across invocations -- .NET has the support; just use a few lines of code to glue them together. Migrate settings with a new version -- a powerful one, available with one line of code. Tooltips (and infotips) -- .NET includes just plain text tooltips; third-party libraries provide richer ones. Diagnostic support -- TraceSources, TraceListeners, and more are built-in. Internationalization -- support for tailoring your app to languages other than your own. LIST B: Components not provided by .NET These are not supplied at all by .NET or supplied only as rudimentary elements requiring substantial work to be realized. Splash screen -- a small window present during program startup with your logo, loading messages, etc. Tip of the day -- a mini-tutorial presented one bit at a time each time the user starts your app. Check for available updates -- facility to query a server to see if the user is running the latest version of your app, then provide a simple way to upgrade if a new version is found. Maximize to multiple monitors -- the canonical window allows you to maximize to a single monitor only; in my apps I allow maximizing across multiple monitors with a click. Taskbar notifier -- flash the taskbar when your backgrounded app has new info for the user. Options dialogs -- multi-page dialogs letting the user customize the app settings to his/her own preferences. Progress indicator -- for long running operations give the user feedback on how far there is left to go. Memory gauge -- an indicator (either absolute or percentage) of how much memory is used by your app. LIST C: Stylistic and/or tiny bits of functionality This list includes bits of functionality that are too tiny to merit being called a component, along with stylistic concerns (that admittedly do overlap with the Windows User Experience Interaction Guidelines). Design a form for resizing -- unless you are restricting your form to be a fixed size, use anchors and docking so that it does what is reasonable when enlarged or shrunk by the user. Set tab order on a form -- repeated tab presses by the user should advance from field to field in a logical order rather than the default order in which you added fields. Adjust controls to be aware of operating modes -- When starting a background operation with, for example, a “Go” button, disable that “Go” button until the operation completes. Provide access keys for all menu items (per UXGuide). Provide shortcut keys for commonly used menu items (per UXGuide). Set up some (global or important or common) shortcut keys without associating to menu items. Allow some menu items to be invoked with or without modifier keys (shift, control, alt) where the modifier key is useful to vary the operation slightly. Hook up Escape and Enter on child forms to do what is reasonable. Decorate any library classes with documentation-comments and attributes -- this allows Visual Studio to leverage them for Intellisense and property descriptions. Spell check your code! What else would you include?

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• Converting C source to C++

  - by Barry Kelly

  How would you go about converting a reasonably large (300K), fairly mature C codebase to C++? The kind of C I have in mind is split into files roughly corresponding to modules (i.e. less granular than a typical OO class-based decomposition), using internal linkage in lieu private functions and data, and external linkage for public functions and data. Global variables are used extensively for communication between the modules. There is a very extensive integration test suite available, but no unit (i.e. module) level tests. I have in mind a general strategy: Compile everything in C++'s C subset and get that working. Convert modules into huge classes, so that all the cross-references are scoped by a class name, but leaving all functions and data as static members, and get that working. Convert huge classes into instances with appropriate constructors and initialized cross-references; replace static member accesses with indirect accesses as appropriate; and get that working. Now, approach the project as an ill-factored OO application, and write unit tests where dependencies are tractable, and decompose into separate classes where they are not; the goal here would be to move from one working program to another at each transformation. Obviously, this would be quite a bit of work. Are there any case studies / war stories out there on this kind of translation? Alternative strategies? Other useful advice? Note 1: the program is a compiler, and probably millions of other programs rely on its behaviour not changing, so wholesale rewriting is pretty much not an option. Note 2: the source is nearly 20 years old, and has perhaps 30% code churn (lines modified + added / previous total lines) per year. It is heavily maintained and extended, in other words. Thus, one of the goals would be to increase mantainability. [For the sake of the question, assume that translation into C++ is mandatory, and that leaving it in C is not an option. The point of adding this condition is to weed out the "leave it in C" answers.]

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• Security review of an authenticated Diffie Hellman variant

  - by mtraut

  EDIT I'm still hoping for some advice on this, i tried to clarify my intentions... When i came upon device pairing in my mobile communication framework i studied a lot of papers on this topic and and also got some input from previous questions here. But, i didn't find a ready to implement protocol solution - so i invented a derivate and as i'm no crypto geek i'm not sure about the security caveats of the final solution: The main questions are Is SHA256 sufficient as a commit function? Is the addition of the shared secret as an authentication info in the commit string safe? What is the overall security of the 1024 bit group DH I assume at most 2^-24 bit probability of succesful MITM attack (because of 24 bit challenge). Is this plausible? What may be the most promising attack (besides ripping the device out off my numb, cold hands) This is the algorithm sketch For first time pairing, a solution proposed in "Key agreement in peer-to-peer wireless networks" (DH-SC) is implemented. I based it on a commitment derived from: A fix "UUID" for the communicating entity/role (128 bit, sent at protocol start, before commitment) The public DH key (192 bit private key, based on the 1024 bit Oakley group) A 24 bit random challenge Commit is computed using SHA256 c = sha256( UUID || DH pub || Chall) Both parties exchange this commitment, open and transfer the plain content of the above values. The 24 bit random is displayed to the user for manual authentication DH session key (128 bytes, see above) is computed When the user opts for persistent pairing, the session key is stored with the remote UUID as a shared secret Next time devices connect, commit is computed by additionally hashing the previous DH session key before the random challenge. For sure it is not transfered when opening. c = sha256( UUID || DH pub || DH sess || Chall) Now the user is not bothered authenticating when the local party can derive the same commitment using his own, stored previous DH session key. After succesful connection the new DH session key becomes the new shared secret. As this does not exactly fit the protocols i found so far (and as such their security proofs), i'd be very interested to get an opinion from some more crypto enabled guys here. BTW. i did read about the "EKE" protocol, but i'm not sure what the extra security level is.

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