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• Blocking HTML and Javascript from being displayed on my site

  - by Tim Powell

  I am working on this new social networking site. One of it's various functions is posting. You can post to Facebook and my site, or Twitter and my site. That being said, I couldn't help but try and post HTML as I was testing sql injection. When I did, I noticed that there where ways to manipulate the site to, for instance, using a element to completely screw up the CSS design, or redirect a user to another site using javascript. That being said, I want to make my site a safe environment for my users... not a site that is used to distribute computer viruses, porn, and other things that might make someone tend to stay off of my site. When I searched this topic, I found ways to "strip" the HTML out of the $post variable before submitting it to the database. However, I would just like to make it so you can post any text, including HTML and Javascript, without the browser interpreting it as "run this..." code: I want to display it as plane text. I've seen it on Facebook, and when I looked at it the source code of a post, it showed <, /, and as regular text. I tried "dissecting" Facebook's source code, but found nothing. I have tried using tags such as <pre> and <code>, but because of the lack of ability to style and control them, I gave up and went back to just allowing HTML. Please, anyone who knows how to do this, please help me out. Thanks in advance, TP

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• x86 Assembly: Before Making a System Call on Linux Should You Save All Registers?

  - by mudge

  I have the below code that opens up a file, reads it into a buffer and then closes the file. The close file system call requires that the file descriptor number be in the ebx register. The ebx register gets the file descriptor number before the read system call is made. My question is should I save the ebx register on the stack or somewhere before I make the read system call, (could int 80h trash the ebx register?). And then restore the ebx register for the close system call? Or is the code I have below fine and safe? I have run the below code and it works, I'm just not sure if it is generally considered good assembly practice or not because I don't save the ebx register before the int 80h read call. ;; open up the input file mov eax,5 ; open file system call number mov ebx,[esp+8] ; null terminated string file name, first command line parameter mov ecx,0o ; access type: O_RDONLY int 80h ; file handle or negative error number put in eax test eax,eax js Error ; test sign flag (SF) for negative number which signals error ;; read in the full input file mov ebx,eax ; assign input file descripter mov eax,3 ; read system call number mov ecx,InputBuff ; buffer to read into mov edx,INPUT_BUFF_LEN ; total bytes to read int 80h test eax,eax js Error ; if eax is negative then error jz Error ; if no bytes were read then error add eax,InputBuff ; add size of input to the begining of InputBuff location mov [InputEnd],eax ; assign address of end of input ;; close the input file ;; file descripter is already in ebx mov eax,6 ; close file system call number int 80h

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• Does "delegate" mean a type or an object?

  - by Michal Czardybon

  Reading from MSDN: "A delegate is a type that references a method. Once a delegate is assigned a method, it behaves exactly like that method." Does then "delegate" mean a type or an object?! ...It cannot be both. It seems to me that the single word is used in two different meanings: a type containing a reference to a method of some specified signature, an object of that type, which can be actually called like a method. I would prefer a more precise vocabulary and use "delegate type" for the first case. I have been recently reading a lot about events and delegates and that ambiguity was making me confused many times. Some other uses of "delegate" word in MSDN in the first meaning: "Custom event delegates are needed only when an event generates event data" "A delegate declaration defines a class that is derived from the class System.Delegate" Some other uses of "delegate" word in MSDN in the second meaning: "specify a delegate that will be called upon the occurrence of some event" "Delegates are objects that refer to methods. They are sometimes described as type-safe function pointers" What do you think? Why did people from Microsoft introduced this ambiguity? Am I the only person to have conceptual problems with different notions being referenced with the same word.

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• Is it OK to write code after [super dealloc]? (Objective-C)

  - by Richard J. Ross III

  I have a situation in my code, where I cannot clean up my classes objects without first calling [super dealloc]. It is something like this: // Baseclass.m @implmentation Baseclass ... -(void) dealloc { [self _removeAllData]; [aVariableThatBelongsToMe release]; [anotherVariableThatBelongsToMe release]; [super dealloc]; } ... @end This works great. My problem is, when I went to subclass this huge and nasty class (over 2000 lines of gross code), I ran into a problem: when I released my objects before calling [super dealloc] I had zombies running through the code that were activated when I called the [self _removeAllData] method. // Subclass.m @implementation Subclass ... -(void) deallloc { [super dealloc]; [someObjectUsedInTheRemoveAllDataMethod release]; } ... @end This works great, and It didn't require me to refactor any code. My question Is this: Is it safe for me to do this, or should I refactor my code? Or maybe autorelease the objects? I am programming for iPhone if that matters any.

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• Combining Java hashcodes into a "master" hashcode

  - by Nick Wiggill

  I have a vector class with hashCode() implemented. It wasn't written by me, but uses 2 prime numbers by which to multiply the 2 vector components before XORing them. Here it is: /*class Vector2f*/ ... public int hashCode() { return 997 * ((int)x) ^ 991 * ((int)y); //large primes! } ...As this is from an established Java library, I know that it works just fine. Then I have a Boundary class, which holds 2 vectors, "start" and "end" (representing the endpoints of a line). The values of these 2 vectors are what characterize the boundary. /*class Boundary*/ ... public int hashCode() { return 1013 * (start.hashCode()) ^ 1009 * (end.hashCode()); } Here I have attempted to create a good hashCode() for the unique 2-tuple of vectors (start & end) constituting this boundary. My question: Is this hashCode() implementation going to work? (Note that I have used 2 different prime numbers in the latter hashCode() implementation; I don't know if this is necessary but better to be safe than sorry when trying to avoid common factors, I guess -- since I presume this is why primes are popular for hashing functions.)

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• #include - brackets vs quotes in XCode?

  - by Chris Becke

  In MSVC++ #include files are searched for differently depending on whether the file is enclosed in "" or <. The quoted form searches first in the local folder, then in /I specified locations, The angle bracket form avoids the local folder. This means, in MSVC++, its possible to have header files with the same name as runtime and SDK headers. So, for example, I need to wrap up the windows sdk windows.h file to undefine some macro's that cause trouble. With MSVS I can just add a (optional) windows.h file to my project as long as I include it using the quoted form :- // some .cpp file #include "windows.h" // will include my local windows.h file And in my windows.h, I can pull in the real one using the angle bracket form: // my windows.h #include <windows.h> // will load the real one #undef ConflictingSymbol Trying this trick with GCC in XCode didn't work. angle bracket #includes in system header files in fact are finding my header files with similar names in my local folder structure. The MSVC system means its quite safe to have a "String.h" header file in my own folder structre. On XCode this seems to be a major no no. Is there some way to control this search path behaviour in XCode to be more like MSVC's? Or do I just have to avoid naming any of my headers anything that might possibly conflict with a system header. Writing cross platform code and using lots of frameworks means the possibility of incidental conflicts seems large.

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• Using stringstream instead of `sscanf` to parse a fixed-format string

  - by John Dibling

  I would like to use the facilities provided by stringstream to extract values from a fixed-format string as a type-safe alternative to sscanf. How can I do this? Consider the following specific use case. I have a std::string in the following fixed format: YYYYMMDDHHMMSSmmm Where: YYYY = 4 digits representing the year MM = 2 digits representing the month ('0' padded to 2 characters) DD = 2 digits representing the day ('0' padded to 2 characters) HH = 2 digits representing the hour ('0' padded to 2 characters) MM = 2 digits representing the minute ('0' padded to 2 characters) SS = 2 digits representing the second ('0' padded to 2 characters) mmm = 3 digits representing the milliseconds ('0' padded to 3 characters) Previously I was doing something along these lines: string s = "20101220110651184"; unsigned year = 0, month = 0, day = 0, hour = 0, minute = 0, second = 0, milli = 0; sscanf(s.c_str(), "%4u%2u%2u%2u%2u%2u%3u", &year, &month, &day, &hour, &minute, &second, &milli ); The width values are magic numbers, and that's ok. I'd like to use streams to extract these values and convert them to unsigneds in the interest of type safety. But when I try this: stringstream ss; ss << "20101220110651184"; ss >> setw(4) >> year; year retains the value 0. It should be 2010. How do I do what I'm trying to do? I can't use Boost or any other 3rd party library, nor can I use C++0x.

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• VS2008 Link Error Using SafeInt3.hpp in 64bit mode.

  - by photo_tom

  I have the below code that links and runs fine in 32bit mode - #include "safeint3.hpp" typedef SafeInt<SIZE_T> SAFE_SIZE_T; SAFE_SIZE_T sizeOfCache; SAFE_SIZE_T _allocateAmt; Where safeint3.hpp is current version that can be found on Codeplex SafeInt. For those who are unaware of it, safeint is a template class that makes working with different integer types and sizes "safe". To quote channel 9 video on software - "it writes the code that you should". Which is my case. I have a class that is managing a large in-memory cache of objects (6gb) and I am very concerned about making sure that I don't have overflow/underflow issues on my pointers/sizes/other integer variables. In this use, it solves many problems. My problem is coming when moving from 32bit dev mode to 64bit production mode. When I build the app in this mode, I'm getting the following linker warnings - 1>cachecontrol.obj : warning LNK4006: "bool __cdecl IntrinsicMultiplyUint64(unsigned __int64 const &,unsigned __int64 const &,unsigned __int64 *)" (?IntrinsicMultiplyUint64@@YA_NAEB_K0PEA_K@Z) already defined in ImageInRamCache.obj; second definition ignored 1>cachecontrol.obj : warning LNK4006: "bool __cdecl IntrinsicMultiplyInt64(__int64 const &,__int64 const &,__int64 *)" (?IntrinsicMultiplyInt64@@YA_NAEB_J0PEA_J@Z) already defined in ImageInRamCache.obj; second definition ignored While I understand I can ignore the error, I would like either (a) prevent the warning from occurring or (b) make it disappear so that my QA department doesn't flag it as a problem. And after spending some time researching it, I cannot find a way to do either.

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• Accessing vars from another clojure namespace?

  - by erikcw

  In my main namespace, I have a top level var named "settings" which is initialized as an empty {}. My -main fn sets the contents of settings using def and conj based on some command line args (different database hosts for production/development, etc). I'm trying to access the contents of this map from another namespace to pull out some of the settings. When I try to compile with lein into an uberjar, I get a traceback saying "No such var: lb/settings". What am I missing? Is there a more idiomatic way to handle app wide settings such as these? Is it safe to use "def" inside of -main like I am, or should I be use an atom or ref to make this threadsafe? Thanks! (ns main (:use ...) (:gen-class)) (def settings {}) (defn -main [& args] (with-command-line-args... ;set devel? based on args (if (true? devel?) (def settings (conj settings {:mongodb {:host "127.0.0.1"} :memcached {:host "127.0.0.1"}})) (def settings (conj settings {:mongodb {:host "PRODUCTION_IP"} :memcached {:host "PRODUCTION_IP"}}))) ;file2.clj (ns some-other-namespace (:require [main :as lb] ...) ;configure MongoDB (congo/mongo! :db "dbname" :host (:host (mongodb lb/settings)))) ...

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• OOP design issue: Polymorphism

  - by Graham Phillips

  I'm trying to solve a design issue using inheritance based polymorphism and dynamic binding. I have an abstract superclass and two subclasses. The superclass contains common behaviour. SubClassA and SubClassB define some different methods: SubClassA defines a method performTransform(), but SubClassB does not. So the following example 1 var v:SuperClass; 2 var b:SubClassB = new SubClassB(); 3 v = b; 4 v.performTransform(); would cause a compile error on line 4 as performTransform() is not defined in the superclass. We can get it to compile by casting... (v as SubClassA).performTransform(); however, this will cause a runtime exception to be thrown as v is actually an instance of SubClassB, which also does not define performTransform() So we can get around that by testing the type of an object before casting it: if( typeof v == SubClassA) { (cast v to SubClassA).performTransform(); } That will ensure that we only call performTransform() on v's that are instances of SubClassA. That's a pretty inelegant solution to my eyes, but at least its safe. I have used interface based polymorphism (interface meaning a type that can't be instantiated and defines the API of classes that implement it) in the past, but that also feels clunky. For the above case, if SubClassA and SubClassB implemented ISuperClass that defined performTransform, then they would both have to implement performTransform(). If SubClassB had no real need for a performTransform() you would have to implement an empty function. There must be a design pattern out there that addresses the issue.

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• Hibernate NamingStrategy implementation that maintains state between calls

  - by Robert Petermeier

  Hi, I'm working on a project where we use Hibernate and JBoss 5.1. We need our entity classes to be mapped to Oracle tables that follow a certain naming convention. I'd like to avoid having to specify each table and column name in annotations. Therefore, I'm currently considering implementing a custom implementation of org.hibernate.cfg.NamingStrategy. The SQL naming conventions require the name of columns to have a suffix that is equivalent to a prefix of the table name. If there is a table "T100_RESOURCE", the ID column would have to be named "RES_ID_T100". In order to implement this in a NamingStrategy, the implementation would have to maintain state, i.e. the current class name it is creating the mappings for. It would rely on Hibernate to always call classToTableName() before propertyToColumnName() and to determine all column names by calling propertyToColumnName() before the next call to classToTableName() Is it safe to do that or are there situations where Hibernate will mix things up? I am not thinking of problems through multiple threads here (which can be solved by keeping the last class name in a ThreadLocal) but also of Hibernate deliberately calling this out of order in certain circumstances. For example Hibernate asking for mappings of three properties of class A, then one of class B, then again more attributes of class A.

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• Adding to page control collection from inside a user control

  - by Zarigani

  I have an asp.net usercontrol which represents a "popup" dialog. Basically, it's a wrapper for the jQuery UI dialog which can be subclassed to easily make dialogs. As part of this control, I need to inject a div into the page the control is used on, either at the very top or very bottom of the form so that when the popup is instantiated, it's parent is changed to this div. This allows "nested" popups without the child popup being trapped inside the parent popup. The trouble is, I can't find a safe way to inject this div into the page. A usercontrol doesn't have a preinit event, so I can't do it there, and calling Page.Form.Controls.Add(...) in Init, Load or PreRender causes the standard exception "The control collection cannot be modified during DataBind, Init, Load, PreRender or Unload phases." I thought I had found a solution by using... ScriptManager.RegisterClientScriptBlock(Page, Me.GetType, UniqueID + "_Dialog_Div", containerDiv, False) ... which seemed to work well normally, but recently a coworker tried putting an UpdatePanel inside the dialog and now she's getting the error "The script tag registered for type 'ASP.controls_order_viewzips_ascx' and key 'ctl00$ContentBody$OViewZips_Dialog_Div' has invalid characters outside of the script tags: . Only properly formatted script tags can be registered." How are you supposed to add controls to the pages control collection from inside a user control?

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• How to perform a Depth First Search iteratively using async/parallel processing?

  - by Prabhu

  Here is a method that does a DFS search and returns a list of all items given a top level item id. How could I modify this to take advantage of parallel processing? Currently, the call to get the sub items is made one by one for each item in the stack. It would be nice if I could get the sub items for multiple items in the stack at the same time, and populate my return list faster. How could I do this (either using async/await or TPL, or anything else) in a thread safe manner? private async Task<IList<Item>> GetItemsAsync(string topItemId) { var items = new List<Item>(); var topItem = await GetItemAsync(topItemId); Stack<Item> stack = new Stack<Item>(); stack.Push(topItem); while (stack.Count > 0) { var item = stack.Pop(); items.Add(item); var subItems = await GetSubItemsAsync(item.SubId); foreach (var subItem in subItems) { stack.Push(subItem); } } return items; } EDIT: I was thinking of something along these lines, but it's not coming together: var tasks = stack.Select(async item => { items.Add(item); var subItems = await GetSubItemsAsync(item.SubId); foreach (var subItem in subItems) { stack.Push(subItem); } }).ToList(); if (tasks.Any()) await Task.WhenAll(tasks); UPDATE: If I wanted to chunk the tasks, would something like this work? foreach (var batch in items.BatchesOf(100)) { var tasks = batch.Select(async item => { await DoSomething(item); }).ToList(); if (tasks.Any()) { await Task.WhenAll(tasks); } } The language I'm using is C#.

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• Ajax request not receiving xml from Django

  - by amougeot

  I have a Django server which handles requests to a URL which will return some HTML for use in an image gallery. I can navigate to the URL and the browser will display the HTML that is returned, but I can't get that same HTML by doing an AJAX call (using jQuery) to the same URL. This is the view that generates the response: def gallery_images(request, gallery_name): return render_to_response('galleryimages.html', {'images': get_images_of_gallery(gallery_name)}, mimetype='text/xml') This is the 'galleryimages.html' template: {% for image in images %} <div id="{{image.name}}big"> <div class="actualImage" style="background-image:url({{image.image.name}});"> <h1>{{image.caption|safe}}</h1> </div> </div> {% endfor %} This is the jQuery call I am making: $("#allImages").load("http://localhost:8000/galleryimages/Web"); However, this loads nothing into my #allImages div. I've used firebug and ran jQuery's Ajax method .get("http://localhost:8000/galleryimages/Web") and firebug says that the response text is completely empty. When I check my Django server log, this is the entry I see for when I navigate to the URL manually, through my browser: [16/Jan/2010 17:34:10] "GET /galleryimages/Web HTTP/1.1" 200 215 This is the entry in the server log for when I make the AJAX call: [16/Jan/2010 17:36:19] "OPTIONS /galleryimages/Web HTTP/1.1" 200 215 Why does the AJAX request not get the xml that my Django page is serving?

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• How do I put all the types matching a particular C# interface in an IDictionary?

  - by Kevin Brassen

  I have a number of classes all in the same interface, all in the same assembly, all conforming to the same generic interface: public class AppleFactory : IFactory<Apple> { ... } public class BananaFactory : IFactory<Banana> { ... } // ... It's safe to assume that if we have an IFactory<T> for a particular T that it's the only one of that kind. (That is, there aren't two things that implement IFactory<Apple>.) I'd like to use reflection to get all these types, and then store them all in an IDictionary, where the key is typeof(T) and the value is the corresponding IFactory<T>. I imagine eventually we would wind up with something like this: _map = new Dictionary<Type, object>(); foreach(Type t in [...]) { object factoryForType = System.Reflection.[???](t); _map[t] = factoryForType; } What's the best way to do that? I'm having trouble seeing how I'd do that with the System.Reflection interfaces.

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• A better way of getting a data table with various column types into string array

  - by Vlad

  This should be an easy one, looks like I got myself too confused. I get a table from a database, data ranges from varchar to int to Null values. Cheap and dirty way of converting this into a tab-delimited file that I already have is this (shrunken to preserve space, ugliness is kept on par with original): da.Fill(dt) ' da - DataAdapter ' ' dt - DataTable ' Dim lColumns As Long = dt.Columns.Count Dim arrColumns(dt.Columns.Count) As String Dim arrData(dt.Columns.Count) As Object Dim j As Long = 0 Dim arrData(dt.Columns.Count) As Object For i = 0 To dt.Rows.Count - 1 arrData = dt.Rows(i).ItemArray() For j = 0 To arrData.GetUpperBound(0) - 1 arrColumns(j) = arrData(j).ToString Next wrtOutput.WriteLine(String.Join(strFieldDelimiter, arrColumns)) Array.Clear(arrColumns, 0, arrColumns.GetLength(0)) Array.Clear(arrData, 0, arrData.GetLength(0)) Next Not only this is ugly and inefficient, it is also getting on my nerves. Besides, I want, if possible, to avoid the infamous double-loop through the table. I would really appreciate a clean and safe way of rewriting this piece. I like the approach that is used here - especially that is trying to solve the same problem that I have, but it crashes on me when I apply it to my case directly.

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• How do I wait for all other threads to finish their tasks?

  - by Mike

  I have several threads consuming tasks from a queue using something similar to the code below. The problem is that there is one type of task which cannot run while any other tasks are being processed. Here is what I have: while (true) // Threaded code { while (true) { lock(locker) { if (close_thread) return; task = GetNextTask(); // Get the next task from the queue } if (task != null) break; wh.WaitOne(); // Wait until a task is added to the queue } task.Run(); } And this is kind of what I need: while (true) { while (true) { lock(locker) { if (close_thread) return; if (disable_new_tasks) { task = null; } else { task = GetNextTask(); } } if (task != null) break; wh.WaitOne(); } if(!task.IsThreadSafe()) { // I would set this to false inside task.Run() at // the end of the non-thread safe task disable_new_tasks = true; Wait_for_all_threads_to_finish_their_current_tasks(); } task.Run(); } The problem is I don't know how to achive this without creating a mess.

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• The best way to predict performance without actually porting the code?

  - by ardiyu07

  I believe there are people with the same experience with me, where he/she must give a (estimated) performance report of porting a program from sequential to parallel with some designated multicore hardwares, with a very few amount of time given. For instance, if a 10K LoC sequential program was given and executes on Intel i7-3770k (not vectorized) in 100 ms, how long would it take to run if one parallelizes the code to a Tesla C2075 with NVIDIA CUDA, given that all kinds of parallelizing optimization techniques were done? (but you're only given 2-4 days to report the performance? assume that you didn't know the algorithm at all. Or perhaps it'd be safer if we just assume that it's an impossible situation to finish the job) Therefore, I'm wondering, what most likely be the fastest way to give such performance report? Is it safe to calculate solely by the hardware's capability, such as GFLOPs peak and memory bandwidth rate? Is there a mathematical way to calculate it? If there is, please prove your method with the corresponding problem description and the algorithm, and also the target hardwares' specifications. Or perhaps there already exists such tool to (roughly) estimate code porting? (Please don't the answer: 'kill yourself is the fastest way.')

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• C++ - Distributing different headers than development

  - by Ben

  I was curious about doing this in C++: Lets say I have a small library that I distribute to my users. I give my clients both the binary and the associated header files that they need. For example, lets assume the following header is used in development: #include <string> ClassA { public: bool setString(const std::string & str); private: std::string str; }; Now for my question. For deployment, is there anything fundamentally wrong with me giving a 'reduced' header to my clients? For example, could I strip off the private section and simply give them this: #include <string> ClassA { public: bool setString(const std::string & str); }; My gut instinct says "yes, this is possible, but there are gotchas", so that is why I am asking this question here. If this is possible and also safe, it looks like a great way to hide private variables, and thus even avoid forward declaration in some cases. I am aware that the symbols will still be there in the binary itself, and that this is just a visibility thing at the source code level. Thanks!

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• Capturing output of find . -print0 into a bash array

  - by Idris

  Using find . -print0 seems to be the only safe way of obtaining a list of files in bash due to the possibility of filenames containing spaces, newlines, quotation marks etc. However, I'm having a hard time actually making find's output useful within bash or with other command line utilities. The only way I have managed to make use of the output is by piping it to perl, and changing perl's IFS to null: find . -print0 | perl -e '$/="\0"; @files=<>; print $#files;' This example prints the number of files found, avoiding the danger of newlines in filenames corrupting the count, as would occur with: find . | wc -l As most command line programs do not support null-delimited input, I figure the best thing would be to capture the output of find . -print0 in a bash array, like I have done in the perl snippet above, and then continue with the task, whatever it may be. How can I do this? This doesn't work: find . -print0 | ( IFS=$'\0' ; array=( $( cat ) ) ; echo ${#array[@]} ) A much more general question might be: How can I do useful things with lists of files in bash?

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• C++ Dynamic Allocation Mismatch: Is this problematic?

  - by acanaday

  I have been assigned to work on some legacy C++ code in MFC. One of the things I am finding all over the place are allocations like the following: struct Point { float x,y,z; }; ... void someFunc( void ) { int numPoints = ...; Point* pArray = (Point*)new BYTE[ numPoints * sizeof(Point) ]; ... //do some stuff with points ... delete [] pArray; } I realize that this code is atrociously wrong on so many levels (C-style cast, using new like malloc, confusing, etc). I also realize that if Point had defined a constructor it would not be called and weird things would happen at delete [] if a destructor had been defined. Question: I am in the process of fixing these occurrences wherever they appear as a matter of course. However, I have never seen anything like this before and it has got me wondering. Does this code have the potential to cause memory leaks/corruption as it stands currently (no constructor/destructor, but with pointer type mismatch) or is it safe as long as the array just contains structs/primitive types?

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• How to make checkboxes have the same submit behavior as other inputs?

  - by Tim Santeford

  I have a search form where several checkboxes are checked by default. When the form submits, as a GET, the url will only contain the list of checkboxes that were left checked. http://www.example.com/page/?checkbox1=yes&checkbox2=yes It is difficult with this scenario to determine the difference between when a user first arrives at this search page and when they submit the form with all checkboxes unchecked because the querystrings look the same. To combat this problem I have started injecting a hidden field before the checkbox with the same name and a 'no' value. When the checkbox is unchecked the browser will send the hidden field's no value and when the checkbox is set then the browser is overriding the hidden field with the checkbox's 'yes' value. <input type="hidden" name="checkbox1" value="no" /> <input type="checkbox" name="checkbox1" value="yes" /> when the user submits the form with all checkboxes unchecked I get this querystring: http://www.example.com/page/?checkbox1=no&checkbox2=no This seems to work on ff, chrome, ie5.5+ so I'am I safe in using this method or is there a better way to make checkboxes submit like inputs and selects?

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• Periodically iterating over a collection that's constantly changing

  - by rwmnau

  I have a collection of objects that's constantly changing, and I want to display some information about objects (my application is multi-threaded, and differently threads are constantly submitting requests to modify an object in the collection, so it's unpredictable), and I want to display some information about what's currently in the collection. If I lock the collection, I can iterate over it and get my information without any problems - however, this causes problems with the other threads, since they could have submitted multiple requests to modify the collection in the meantime, and will be stalled. I've thought of a couple ways around this, and I'm looking for any advice. Make a copy of the collection and iterate over it, allowing the original to continue updating in the background. The collection can get large, so this isn't ideal, but it's safe. Iterate over it using a For...Next loop, and catch an IndexOutOfBounds exception if an item is removed from the collection while we're iterating. This may occasionally cause duplicates to appear in my snapshot, so it's not ideal either. Any other ideas? I'm only concerned about a moment-in-time snapshot, so I'm not concerned about reflecting changes in my application - my main concern is that the collection be able to be updated with minimal latency, and that updates never be lost.

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• Why would one want to use the public constructors on Boolean and similar immutable classes?

  - by Robert J. Walker

  (For the purposes of this question, let us assume that one is intentionally not using auto(un)boxing, either because one is writing pre-Java 1.5 code, or because one feels that autounboxing makes it too easy to create NullPointerExceptions.) Take Boolean, for example. The documentation for the Boolean(boolean) constructor says: Note: It is rarely appropriate to use this constructor. Unless a new instance is required, the static factory valueOf(boolean) is generally a better choice. It is likely to yield significantly better space and time performance. My question is, why would you ever want to get a new instance in the first place? It seems like things would be simpler if constructors like that were private. For example, if they were, you could write this with no danger (even if myBoolean were null): if (myBoolean == Boolean.TRUE) It'd be safe because all true Booleans would be references to Boolean.TRUE and all false Booleans would be references to Boolean.FALSE. But because the constructors are public, someone may have used them, which means that you have to write this instead: if (Boolean.TRUE.equals(myBoolean)) But where it really gets bad is when you want to check two Booleans for equality. Something like this: if (myBooleanA == myBooleanB) ...becomes this: if ( (myBooleanA == null && myBooleanB == null) || (myBooleanA == null && myBooleanA.equals(myBooleanB)) ) I can't think of any reason to have separate instances of these objects which is more compelling than not having to do the nonsense above. What say you?

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• Is Domain Anaemia appropriate in a Service Oriented Architecture?

  - by Stimul8d

  I want to be clear on this. When I say domain anaemia, I mean intentional domain anaemia, not accidental. In a world where most of our business logic is hidden away behind a bunch of services, is a full domain model really necessary? This is the question I've had to ask myself recently since working on a project where the "domain" model is in reality a persistence model; none of the domain objects contain any methods and this is a very intentional decision. Initially, I shuddered when I saw a library full of what are essentially type-safe data containers but after some thought it struck me that this particular system doesn't do much but basic CRUD operations, so maybe in this case this is a good choice. My problem I guess is that my experience so far has been very much focussed on a rich domain model so it threw me a little. The remainder of the domain logic is hidden away in a group of helpers, facades and factories which live in a separate assembly. I'm keen to hear what people's thoughts are on this. Obviously, the considerations for reuse of these classes are much simpler but is really that great a benefit?

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