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• Client Server communication in Java - which approach to use?

  - by markovuksanovic

  I have a typical client server communication - Client sends data to the server, server processes that, and returns data to the client. The problem is that the process operation can take quite some time - order of magnitude - minutes. There are a few approaches that could be used to solve this. Establish a connection, and keep it alive, until the operation is finished and the client receives the response. Establish connection, send data, close the connection. Now the processing takes place and once it is finished the server could establish a connection to the client to send the data. Establish a connection, send data, close the connection. Processing takes place. client asks server, every n minutes/seconds if the operation is finished. If the processing is finished the client fetches the data. I was wondering which approach would be the best way to use. Is there maybe some "de facto" standard for solving this problem? How "expensive" is opening a socket in Java? Solution 1. seems pretty nasty to me, but 2. and 3. could do. The problem with solution 2. is that the server needs to know on which port the client is listening, while solution 3. adds some network overhead.

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• What are the interets of synthetic methods?

  - by romaintaz

  Problem One friend suggested an interesting problem. Given the following code: public class OuterClass { private String message = "Hello World"; private class InnerClass { private String getMessage() { return message; } } } From an external class, how may I print the message variable content? Of course, changing the accessibility of methods or fields is not allowed. (the source here, but it is a french blog) Solution The code to solve this problem is the following: try { Method m = OuterClass.class.getDeclaredMethod("access$000", OuterClass.class); OuterClass outerClass = new OuterClass(); System.out.println(m.invoke(outerClass, outerClass)); } catch (Exception e) { e.printStackTrace(); } Note that the access$000 method name is not really standard (even if this format is the one that is strongly recommanded), and some JVM will name this method access$0. Thus, a better solution is to check for synthetic methods: Method method = null; int i = 0; while ((method == null) && (i < OuterClass.class.getDeclaredMethods().length)) { if (OuterClass.class.getDeclaredMethods()[i].isSynthetic()) { method = OuterClass.class.getDeclaredMethods()[i]; } i++; } if (method != null) { try { System.out.println(method.invoke(null, new OuterClass())); } catch (Exception e) { e.printStackTrace(); } } So the interesting point in this problem is to highlight the use of synthetic methods. With these methods, I can access a private field as it was done in the solution. Of course, I need to use reflection, and I think that the use of this kind of thing can be quite dangerous... Question What is the interest - for me, as a developer - of a synthetic method? What can be a good situation where using the synthetic can be useful?

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• 2-column table with two foreign keys. Performance/design question.

  - by Emanuel

  Hello everyone! I recently ran into a quite complex problem and after looking around a lot I couldn't find a solution to it. I've found answers to my questions many times before on stackoverflow.com, so I decided to post here. So I'm making a user/group managment system for a web-based project, and I'm storing all related data into a postgreSQL database. This system relies on three tables: USERS GROUPS GROUP_USERS The two first tables simply define all the users and all the groups on the site, and the last table, GROUP_USERS, stores the groups every user is part of. It only has two columns: USER_ID GROUP_ID Since every user can be a member of several groups, I decided to make a separate table for this purpose, rather than storing a comma separated column in the USERS-table. Now, both columns are foreign keys, and I want to make them both primary keys as well, this since each combination of USER_ID and GROUP_ID has to be unique, and if I give them the constraint UNIQUE pgAdmin tells me that each table should have at least one Primary key. But now I am stuck with what seems to be a lot of indexes and relations to a very small table only containing numbers. In the end, I want this table to be as fast as possible, even if containing tens of thousands of rows. Size on disk shouldn't be a problem since its just all numbers anyway, but it feels quite stupid to have a full-sized index refering to a smaller table. Should I stick with my current solution, store comma-separated values in a column in the USERS-table or is there any other solution I should be aware of. PS. I don't want to use an array-column, even if they are supported by postgreSQL. I want to be as generic as possible so I can switch database later on, if necessary. EDIT: I other words, will using a compound primary key and two foreign keys in one table with only two columns have a negative impact on performance rather than the opposite due to the size of the generated index? Thank you!

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• How to **delete-protect** a file or folder on Windows Server 2003 and onwards using C#/Vb.Net?

  - by Steve Johnson

  Hi all, Is it possible to delete-protect a file/folder using Registry or using a custom written Windows Service in C#? Using Folder Permissions it is possible, but i am looking for a solution that even restricts the admin from deleting specific folders. The requirement is that the administrator must not be easily track the nature of protection and/or may not be able to avert it easily. Obviously all administrators will be able to revert the procedure if the technique is clearly understood. Like folder Permissions/OwnerShip Settings can easily be reset by an administrator. SO that is not an option. Folder protection software can easily be uninstalled and show clear indication that a particular folder is protected by some special kind of software. SO that too is not an option. Most antivirus programs protect folders and files in Program Dir. Windows itself doesnt allow certain files such as registry files in c:\windows\system32\config to not even copied. Such a protection is desired for folders which allowse to read and write to files but not allow deletion. Similar functionality is desired. The protection has to seemless and invisible. I do not want to use any protection features like FolderLock and Invisible secrets/PC Security and Desktop password etc. Moreover, the solution has to be something other than folder encryption. The solution has to be OS-native so ** that it may implemented ** pro grammatically using C#/VB.Net. Please help. Thanks

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• Creating serializeable unique compile-time identifiers for arbitrary UDT's.

  - by Endiannes

  I would like a generic way to create unique compile-time identifiers for any C++ user defined types. for example: unique_id<my_type>::value == 0 // true unique_id<other_type>::value == 1 // true I've managed to implement something like this using preprocessor meta programming, the problem is, serialization is not consistent. For instance if the class template unique_id is instantiated with other_type first, then any serialization in previous revisions of my program will be invalidated. I've searched for solutions to this problem, and found several ways to implement this with non-consistent serialization if the unique values are compile-time constants. If RTTI or similar methods, like boost::sp_typeinfo are used, then the unique values are obviously not compile-time constants and extra overhead is present. An ad-hoc solution to this problem would be, instantiating all of the unique_id's in a separate header in the correct order, but this causes additional maintenance and boilerplate code, which is not different than using an enum unique_id{my_type, other_type};. A good solution to this problem would be using user-defined literals, unfortunately, as far as I know, no compiler supports them at this moment. The syntax would be 'my_type'_id; 'other_type'_id; with udl's. I'm hoping somebody knows a trick that allows implementing serialize-able unique identifiers in C++ with the current standard (C++03/C++0x), I would be happy if it works with the latest stable MSVC and GNU-G++ compilers, although I expect if there is a solution, it's not portable.

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• memory usage in iOS

  - by varun

  My app has a simple UI interface having simple buttons, date picker, picker view, table view, action sheet, toolbar, alert boxes etc. No images, no network access. Just plain simple UI. It accesses SQLite database a lot. ARC option is enabled. I have many questions to ask: In .h files, I am defining IBOutlets like @property(nonatomic, retain) IBOutlet UIButton *bt; Where do i need to do bt=nil? in didReceiveMemoryWarning or viewDidLoad Live Bytes in Instruments tool is 4-5MB. Is it enough or I need to reduce memory usage? If so, how can I do so? Please mention few important points. Also, what all need to be added to the following methods? applicationDidReceiveMemoryWarning UIApplicationDidReceiveMemoryWarningNotification

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• Replace every word with tag

  - by Sherif elKhatib

  JAVASCRIPT or JAVA solution needed The solution I am looking for could use java or javascript. I have the html code in a string so I could manipulate it before using it with java or afterwards with javascript. problem Anyway, I have to wrap each word with a tag. For example: <html> ... > Hello every one, cheers < ... </html> should be changed to <html> ... > <word>Hello</word> <word>every</word> <word>one</word>, <word>cheers</word> < ... </html> JAVASCRIPT hint I am using the following code to highlight a word; however, this will highlight the whole text belonging to a certain tag. When each word is a tag, this will work to some extent. If there is a substitute that will allow me to highlight a word at a certain position, it would also be a solution. function highlightElementAtPoint(xOrdinate, yOrdinate) { var theElement = document.elementFromPoint(xOrdinate, yOrdinate); selectedElement = theElement; theElement.style.backgroundColor = "yellow"; var theName = theElement.nodeName; var theArray = document.getElementsByTagName(theName); var theIndex = -1; for (i = 0; i < theArray.length; i++) { if (theArray[i] == theElement) { theIndex = i; } } window.androidselection.selected(theElement.innerHTML); return theName + " " + theIndex; }

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• Alternate colors on click with jQuery

  - by Jace Cotton

  I'm sure there is a simple solution to this, and I'm sure this is a duplicate question, though I have been unable to solve my solution particularly because I don't really know how to phrase it in order to search for other questions/solutions, so I'm coming here hoping for some help. Basically, I have spans with classes that assigns a background-color property, and inside those spans are words. I have three of these spans, and each time a user clicks on a span I want the class to change (thus changing the background color and inner text). HTML: <span class="alternate"> <span class="blue showing">Lorem</span> <span class="green">Ipsum</span> <span class="red">Dolor</span> </span> CSS: .alternate span { display : none } .alternate .showing { display : inline } .blue { background : blue } .green { background : green } .red { background : red } jQuery: $(".alternate span").each(function() { $(this).on("click", function() { $(this).removeClass("showing"); $(this).next().addClass("showing"); }); }); This solution works great using $.next until I get to the third click, whereafter .showing is removed, and is not added since there are no more $.next options. How do I, after getting to the last-child, add .showing to the first-child and then start over? I have tried various options including if($(".alternate span:last-child").hasClass("showing")) { etc. etc. }, and I attempted to use an array and for loop though I failed to make it work. Newb question, I know, but I can't seem to solve this so as a last resort I'm coming here.

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• Optimization of a c++ matrix/bitmap class

  - by Andrew

  I am searching a 2D matrix (or bitmap) class which is flexible but also fast element access. The contents A flexible class should allow you to choose dimensions during runtime, and would look something like this (simplified): class Matrix { public: Matrix(int w, int h) : data(new int[x*y]), width(w) {} void SetElement(int x, int y, int val) { data[x+y*width] = val; } // ... private: // symbols int width; int* data; }; A faster often proposed solution using templates is (simplified): template <int W, int H> class TMatrix { TMatrix() data(new int[W*H]) {} void SetElement(int x, int y, int val) { data[x+y*W] = val; } private: int* data; }; This is faster as the width can be "inlined" in the code. The first solution does not do this. However this is not very flexible anymore, as you can't change the size anymore at runtime. So my question is: Is there a possibility to tell the compiler to generate faster code (like when using the template solution), when the size in the code is fixed and generate flexible code when its runtime dependend? I tried to achieve this by writing "const" where ever possible. I tried it with gcc and VS2005, but no success. This kind of optimization would be useful for many other similar cases.

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• How To: Call a web service from ajax

  - by Kolten

  I have a simple Web Service that send email and is called via: public bool SendMail(string format, string from, string to, string cc, string bcc, string subject, string body, string replyTo) I have never used ajax before, and find I need to call this service and pass form contents to it from a simple html page (I cannot use asp or asp.net unfortunately). Can I get a quick rundown of what is required? I have searched for simple examples, but find I am having difficulty understanding how to call it and pass the parameters required of the Web Service. Thanks all!

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• What could the negative effects be of attaching to a process as a debugger?

  - by I_like_traffic_lights

  Background A client of mine has a major problem. They have a CRM system, which was created by a single person over a period of 9 years. Unfortunatelly, a few weeks ago, this person died. I believe the company has learned their lesson, and they have started a project of rewriting the CRM system to a modern platform. I have been hired to create a solution in the meantime to make adaptations to the CRM system. I have given up understanding the code, as this would take too long. My solution, is therefore, to make a window and show this on top of the CRM system, whenever this CRM system is showing. This part works fine, but my major problem is extracting the data from the CRM system. Proposed solution After excluding 6 approaches, including runtime code injection, memory searching, database integration, I have arrived at attaching to the process as a debugger, so I get notified about event, and use this in combination with reading from process memory. This approach seems to work, but I am worried about possible side-effects of this approach. Question What are the dangers of using this in a production environment, where there are 250 employees utilizing the system. Needless to say, I cannot risk reducing the already shaky stability of the system.

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• .NET security mechanism to restrict access between two Types in the same project?

  - by jdk

  Question: Is there a mechanism in the .NET Framework to hide one custom Type from another without using separate projects/assemblies? I'm using C# with ASP.NET in a Website project. Note: I'm not talking about access modifiers to hide members of a Type from another type - I mean to hide the Type itself. Background: I'm working in an ASP.NET Website project and the team has decided not to use separate project assemblies for different software layers. Therefore I'm looking for a way to have, for example, a DataAccess/ folder of which I disallow its classes to access other Types in the same ASP.NET Website project. In other words I want to fake the layers and have some kind of security mechanism around each layer to prevent it from accessing another. Obviously there's not a way to enforce this restriction using language-specific OO keywords so I am looking for something else, for example: maybe a permission framework or code access mechanism, maybe something that uses meta data like Attributes. Even something that restricts one namespace from accessing another. I'm unsure the final form it might take. If this were C++ I'd likely be using friend to make as solution, which doesn't translate to C# internal in this case although they're often compared. I don't really care whether the solution actually hides Types from each other or just makes them inaccessible; however I don't want to lock down one Type from all others, another reason access modifiers are not a solution. A runtime or design time answer will suffice. Looking for something easy to implement otherwise it's not worth the effort ...

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• How do I determine darker or lighter color variant of a given color?

  - by Nidonocu

  Given a source color of any hue by the system or user, I'd like a simple algorithm I can use to work out a lighter or darker variants of the selected color. Similar to effects used on Windows Live Messenger for styling the user interface. Language is C# with .net 3.5. Responding to comment: Color format is (Alpha)RGB. With values as bytes or floats. Marking answer: For the context of my use (a few simple UI effects), the answer I'm marking as accepted is actually the most simple for this context. However, I've given up votes to the more complex and accurate answers too. Anyone doing more advanced color operations and finding this thread in future should definitely check those out. Thanks SO. :)

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• Wordpress jQuery Post Attachment Image Gallery?

  - by LearnWebCode

  Hi everyone, Curious if any of you have a good solution for the following situation... because I've never thought of anything myself and usually have to resort to custom fields like "post-image-1" through "post-image-10" and manually paste the file name of a jpg in. Which is a horrible solution and only works for tech savvy posters. Basically I want non-tech savvy users to be able to upload / attach (but not insert into the actual post content) multiple images to a post, which will be turned into a makeshift gallery. Then I want to output these attachments in a list down the page after the post, using basic jQuery lightbox gallery functionality. It doesn't have to be through attachments, it could be a stand alone plugin, as long as it offers customizable markup. Basically any solution that would achieve the same thing would be incredible. Has anyone done this before? Am I missing something terribly obvious? I don't even know what exactly to call this, so I haven't had much luck with my Google research so far :( Thanks!

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• Regex to GENERATE thumbnails!?!?! (but that's crazy!)

  - by CryptoMonkey

  Hello everyone! So here is my situation, and the solution that I've come up with to solve the problem. I have created an application that includes TinyMCE to allow users to create HTML content for publishing. The user can include images in their markup, and drag/resize those images effecting the final Width/Height attributes in the IMG tag. This is all great, the users can include images and resize/relocate them to their desired appearance. But one big problem is that I am now sending a (possibly) much larger image to the client, only to have the browser resize the image into the requested Width/Height attributes. All that bandwidth and lost load time.... So my solution is to pre-process my users markup content, scanning all of the IMG tags and parsing out the Height/Width/Src attributes. Then set each img's SRC tag to a phpThumb request with the parsed Height/Width passed into the thumbnails URL. This will create my reduced size image (optimising bandwidth at the expense of CPU and caching). What do you think about this solution? I've seen other posts where people were using mod_rewrite to do something similar, but I want to effect the content on the page service and not manipulate the image requests as they're being received. .... Any thoughts about this design? I need some help with the fine details as my regex skills need some work, but I'm very short on time and promise to pay my technical knowledge debt soon. To make the regex's easier, I can be sure of some things. Only img tags that need this processing will have an existing width="" height="" attributes (with the double quotes, and lower cased text, but I suppose matching the text case insensitive would be better if TinyMCE changes) So a regex to match only the necessary Img tags, and maybe another three regex's to extract the src, the width, and the height? Thanks everyone.

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• Read header data from files on remote server

  - by rejeep

  Hi! I'm working on a project right now where I need to read header data from files on remote servers. I'm talking about many and large files so I cant read whole files, but just the header data I need. The only solution I have is to mount the remote server with fuse and then read the header from the files as if they where on my local computer. I've tried it and it works. But it has some drawbacks. Specially with FTP: Really slow (FTP is compared to SSH with curlftpfs). From same server, with SSH 90 files was read in 18 seconds. And with FTP 10 files in 39 seconds. Not dependable. Sometimes the mountpoint will not be unmounted. If the server is active and a passive mounting is done. That mountpoint and the parent folder gets locked in about 3 minutes. Does timeout, even when there's data transfer going (guess this is the FTP-protocol and not curlftpfs). Fuse is a solution, but I don't like it very much because I don't feel that I can trust it. So my question is basically if there's any other solutions to the problem. Language is preferably Ruby, but any other will work if Ruby does not support the solution. Thanks!

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• Given a linked list of numbers. Swap every 2 adjacent links.

  - by Learner

  Given a linked list of numbers. Swap every 2 adjacent links. For eg if a linked list given to you is- a-b-c-d-e-f O/p expected- b-a-d-c-f-e Every 2 alternate links have to be swapped. I have written a solution here. Can you suggest me some other solution. Can you comment on my solution and help me better write it? void SwapAdjacentNodes (Node head) { if (head == null) return; if (head.next == null) return; Node curr = head; Node next = curr.Next; Node temp = next.Next; while (true) { temp = next.Next; next.Next = curr; curr.Next = temp; if (curr.Next != null) curr = curr.Next; else break; if (curr.Next.Next!=null) next = curr.Next.Next; else break; } }

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• Retrieve E-mail from server (pop3) by date for filtering on subject or body in C#

  - by Josh

  I have a piece of monitoring software I am writing which needs to retrieve e-mails sent to an address for a certain day so that I can filter them by a regex in the subject or body. I don't need to retrieve the entire message, only the subject and body for all messages on a given day so that I can evaluate them with a regular expression for a token. I looked at EAGetMail as a solution, but their implementation doesn't do what I need to to do. I can only get all information on mail, which only has the size and index. I would need it by subject, but even then I don't want to get everything in inbox. If I went with this solution I have to get all mail, and then retrieve each mail message individually to evaluate the subject and body. This is not ideal. I also looked at OpenPop.Net, but it too does not have a targeted retrieval for today's messages only. Can I even do what I want without looping through every single email on the server until I find a match? What is the best way to accomplish what I am trying to do? Am I going to have to build a custom web request to get the data I want? Also, I looked at Chilkat, but I am looking for a free solution, even if it means building the http request myself.

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• How to properly manage a complex DB structure?

  - by errr

  Let's say you have several systems using the same DB - each uses several schemes (sometimes same as the other). This structure of these schemes is somewhat very big and complicated. Now, how could you possibly manage such scheme structure? Obviously using some sort of "configuration" - the simplest would be SQL scripts, but a more reasonable solution would be XMLs which can be easily converted into SQL, or some other readable solution (for example, JPA's XMLs or Annotations). This solution though, causes a problem where you can't really tell if your configuration matches the structure of the DB schemes exactly. You can't say if those two are synchronized. Why wouldn't they? Well, in such big structure there are going to be many changes, and you won't always remember to save/commit your configuration after you've altered the schemes, or maybe you did save/commit it, but eventually didn't altered anything in the schemes and forgot to undo the changes to the configuration. More than that, another problem (not caused by the configuration, but isn't addressed by it either) is versioning. I don't see any good way of managing the DB schemes versions (say our last alteration makes 3 systems crash - not good, how to "rollback"?). And thoughts? thx.

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• Applying iterative algorithm to a set of rows from database

  - by Corvin

  Hello, this question may seem too basic to some, but please bear with be, it's been a while since I dealt with decent database programming. I have an algorithm that I need to program in PHP/MySQL to work on a website. It performs some computations iteratively on an array of objects (it ranks the objects based on their properties). In each iteration the algorithm runs through all collection a couple of times, accessing various data from different places of the whole collection. The algorithm needs several hundred iterations to complete. The array comes from a database. The straightforward solution that I see is to take the results of a database query and create an object for each row of the query, put the objects to an array and pass the array to my algorithm. However, I'm concerned with efficacy of such solution when I have to work with an array of several thousand of items because what I do is essentially mirror the results of a query to memory. On the other hand, making database query a couple of times on each iteration of the algorithm also seems wrong. So, my question is - what is the correct architectural solution for a problem like this? Is it OK to mirror the query results to memory? If not, which is the best way to work with query results in such an algorithm? Thanks!

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• rails separate login for an api

  - by Squadrons

  I have a very simple api that is part of a rails app that requires logging in. I just need a way to make the api part accessible with a simple form that allows the user to enter parameters like a key (just a simple one stored in the DB, no OAuth or anything), a userId to find and return a user via json, and maybe some other parameters like asking for their schedule. How can I keep this seperate from the rest of the app, making it a public facing form that will grant access only to the api? Thanks.

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• Java - Post to Twitter

  - by Ibolit

  Hi. I've written a simple web application, which i want to post tweets. I have seen some java libraries for working with twitter, and they all seem like too much of work for something that seemingly simple. But it is possible that i am missing something. And I am yet to make any of them work... Is there any simple way to post a tweet in twitter from a web-app in java with only a few lines of code? Thank you very much.

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• Change Default Winform Icon Across Entire App

  - by Kyle Gagnet

  Can I change the default icon used on a Winform? Most of my forms have their icon property set to a custom icon. For the few forms that slip through the cracks, I don't want the generic "hey look, he made this in visual studio" icon. One solution is to tediously check every one of my forms to make sure they either have a custom icon set or have ShowIcon set to False. Another solution is to have every one of my forms inherit from a base class that sets a custom icon in the constructor. Aside from those solutions, what other options do I have? EDIT: I was hoping there would be a way to replace the source of the stock icon with my own. Is it in a resource file somewhere? Or is it embedded in a .NET dll that I can't (or really, really shouldn't) modify? BOUNTY EDIT: Is there a way to accomplish this without editing or writing a single line of code? I don't care how impractical, complicated, waste-of-time the solution is... I just want to know if it's possible. I need to satisfy my curiosity.

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• Automated browser testing: How to test JavaScript in web pages?

  - by Dave

  I am trying to write an application that will test a series of web-pages programmatically. The web pages being tested have JavaScript embedded within them which alter the structure of the HTML when they complete execution. It is then the goal to take the final HTML (post-execution of the embedded JavaScript) and compare it against a known output. Essentially, the Input --- Output for the test application is: URL ---[retrieve HTML]--- HTML ---[execute JS, then compare]--- PASS/FAIL Here is the challenge: I have been unable to find a solution that is able to take the HTML I retrieve from the URL and process the JavaScript, as a browser would, and generate the final HTML a user might see from "View Source" on the same page within the browser. It would be very surprising if this sort of approach has not been made before, so I'm hoping someone out there knows of a fitting solution for this application/problem? If at all possible, I'm hoping for a solution that integrates with .NET (I've tried using the WebBrowser, with no luck). However, if there is an existing 3rd party application that can do exactly this, that would be quite acceptable. Thanks in advance for the suggestions! Dave

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• What open source C/C++ audio compression options are there besides LAME MP3?

  - by Ole Jak

  Are there any C/C++ open source audio encoder besides LAME MP3? It doesn't need to be exactly mp3 format, I need a "compressed digital audio file". I do not want to use Lame because it is too big while no programmer can answer a simple question on it (share simple but easily downloadable and readable project containing only needed 2 simple functions... So I'm tired of searching for help with it.. I need something fresh powerful but more readable than this lib I found (mp3stego) ) "I don't want LAME because I am a fighter with its monopoly" Haha..

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