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• one two-directed tcp socket OR two one-directed? (linux, high volume, low latency)

  - by osgx

  Hello I need to send (interchange) a high volume of data periodically with the lowest possible latency between 2 machines. The network is rather fast (e.g. 1Gbit or even 2G+). Os is linux. Is it be faster with using 1 tcp socket (for send and recv) or with using 2 uni-directed tcp sockets? The test for this task is very like NetPIPE network benchmark - measure latency and bandwidth for sizes from 2^1 up to 2^13 bytes, each size sent and received 3 times at least (in teal task the number of sends is greater. both processes will be sending and receiving, like ping-pong maybe). The benefit of 2 uni-directed connections come from linux: http://lxr.linux.no/linux+v2.6.18/net/ipv4/tcp_input.c#L3847 3847/* 3848 * TCP receive function for the ESTABLISHED state. 3849 * 3850 * It is split into a fast path and a slow path. The fast path is 3851 * disabled when: ... 3859 * - Data is sent in both directions. Fast path only supports pure senders 3860 * or pure receivers (this means either the sequence number or the ack 3861 * value must stay constant) ... 3863 * 3864 * When these conditions are not satisfied it drops into a standard 3865 * receive procedure patterned after RFC793 to handle all cases. 3866 * The first three cases are guaranteed by proper pred_flags setting, 3867 * the rest is checked inline. Fast processing is turned on in 3868 * tcp_data_queue when everything is OK. All other conditions for disabling fast path is false. And only not-unidirected socket stops kernel from fastpath in receive

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• How to implement a network protocol?

  - by gotch4

  Here is a generic question. I'm not in search of the best answer, I'd just like you to express your favourite practices. I want to implement a network protocol in Java (but this is a rather general question, I faced the same issues in C++), this is not the first time, as I have done this before. But I think I am missing a good way to implement it. In fact usually it's all about exchanging text messages and some byte buffers between hosts, storing the status and wait until the next message comes. The problem is that I usually end up with a bunch of switch and more or less complex if statements that react to different statuses / messages. The whole thing usually gets complicated and hard to mantain. Not to mention that sometimes what comes out has some "blind spot", I mean statuses of the protocol that have not been covered and that behave in a unpredictable way. I tried to write down some state machine classes, that take care of checking start and end statuses for each action in more or less smart ways. This makes programming the protocol very complicated as I have to write lines and lines of code to cover every possible situation. What I'd like is something like a good pattern, or a best practice that is used in programming complex protocols, easy to mantain and to extend and very readable. What are your suggestions?

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• MySQL "OR MATCH" hangs (very slow) on multiple tables

  - by Kerry

  After learning how to do MySQL Full-Text search, the recommended solution for multiple tables was OR MATCH and then do the other database call. You can see that in my query below. When I do this, it just gets stuck in a "busy" state, and I can't access the MySQL database. SELECT a.`product_id`, a.`name`, a.`slug`, a.`description`, b.`list_price`, b.`price`, c.`image`, c.`swatch`, e.`name` AS industry, MATCH( a.`name`, a.`sku`, a.`description` ) AGAINST ( '%s' IN BOOLEAN MODE ) AS relevance FROM `products` AS a LEFT JOIN `website_products` AS b ON (a.`product_id` = b.`product_id`) LEFT JOIN ( SELECT `product_id`, `image`, `swatch` FROM `product_images` WHERE `sequence` = 0) AS c ON (a.`product_id` = c.`product_id`) LEFT JOIN `brands` AS d ON (a.`brand_id` = d.`brand_id`) INNER JOIN `industries` AS e ON (a.`industry_id` = e.`industry_id`) WHERE b.`website_id` = %d AND b.`status` = %d AND b.`active` = %d AND MATCH( a.`name`, a.`sku`, a.`description` ) AGAINST ( '%s' IN BOOLEAN MODE ) OR MATCH ( d.`name` ) AGAINST ( '%s' IN BOOLEAN MODE ) GROUP BY a.`product_id` ORDER BY relevance DESC LIMIT 0, 9 Any help would be greatly appreciated. EDIT All the tables involved are MyISAM, utf8_general_ci. Here's the EXPLAIN SELECT statement: id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY a ALL NULL NULL NULL NULL 16076 Using temporary; Using filesort 1 PRIMARY b ref product_id product_id 4 database.a.product_id 2 1 PRIMARY e eq_ref PRIMARY PRIMARY 4 database.a.industry_id 1 1 PRIMARY <derived2> ALL NULL NULL NULL NULL 23261 1 PRIMARY d eq_ref PRIMARY PRIMARY 4 database.a.brand_id 1 Using where 2 DERIVED product_images ALL NULL NULL NULL NULL 25933 Using where I don't know how to make that look neater -- sorry about that UPDATE it returns the query after 196 seconds (I think correctly). The query without multiple tables takes about .56 seconds (which I know is really slow, we plan on changing to solr or sphinx soon), but 196 seconds?? If we could add a number to the relevance if it was in the brand name ( d.name ), that would also work

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• WPF - Extend ListView with checkable AND selectable ListViewItems

  - by Marks

  Hi there. I already read many examples on extending ListViews with checkboxes bound with IsSelected. But I want something more. I want a seperation between the checked and selected state, so i get a ListBox that has a single selected item, but can have multiple checked items. Unfortunately ListViewItem does not have a property for checked and I dont see a possibility to get the ListView to work with a custom CheckableListViewItem. Of course i could use a List of objects with a checked property as ItemSource, but I dont think thats a good way to go. Checked or not is a matter of the list or item-container, not of the object listed in it. Beside that I dont want all my classes like user, role, group to have counterparts like checkableUser, checkableRole and checkableGroup. The behaviour i want can be easyly accomblished for the UI with a <DataTemplate x:Key="CheckBoxCell"> <StackPanel Orientation="Horizontal"> <CheckBox /> </StackPanel> </DataTemplate> and a <GridViewColumn CellTemplate="{StaticResource CheckBoxCell}" Width="30"/> But without a binding on the checkbox i cant check if it is checked or not. Is there any way to accomplish something like that? The perfect solution for me would be to have listView1.SelectedItem, listView1.CheckedItems and maybe a listView1.UncheckedItems and of course listView1.CheckItem and listView1.UncheckItem. Thanks for any help.

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• Get part of array string

  - by user1560295

  Hello my output PHP code is : Array ( [country] => BG - Bulgaria ) ... and he comes from here : <?php $ip = $_SERVER['REMOTE_ADDR']; print_r(geoCheckIP($ip)); //Array ( [domain] => dslb-094-219-040-096.pools.arcor-ip.net [country] => DE - Germany [state] => Hessen [town] => Erzhausen ) //Get an array with geoip-infodata function geoCheckIP($ip) { //check, if the provided ip is valid if(!filter_var($ip, FILTER_VALIDATE_IP)) { throw new InvalidArgumentException("IP is not valid"); } //contact ip-server $response=@file_get_contents('http://www.netip.de/search?query='.$ip); if (empty($response)) { throw new InvalidArgumentException("Error contacting Geo-IP-Server"); } //Array containing all regex-patterns necessary to extract ip-geoinfo from page $patterns=array(); $patterns["country"] = '#Country: (.*?)&nbsp;#i'; //Array where results will be stored $ipInfo=array(); //check response from ipserver for above patterns foreach ($patterns as $key => $pattern) { //store the result in array $ipInfo[$key] = preg_match($pattern,$response,$value) && !empty($value[1]) ? $value[1] : ''; } return $ipInfo; } ?> How can I get ONLY the name of the Country like in my case "Bulgaria"? I think it will happen with preg_replace or substr but i dont know what is the better solution now.

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• Can someone confirm how Microsoft Excel 2007 internally represents numbers?

  - by Jon

  I know the IEEE 754 floating point standard by heart as I had to learn it for an exam. I know exactly how floating point numbers are used and the problems that they can have. I can manually do any operation on the binary representation of floating point numbers. However, I have not found a single source which unambiguously states that excel uses 64 bit floating point numbers to internally represent every single cell "type" in excel except for text. I have no idea whether some of the types use signed or unsigned integers and some use 64 bit floating point. I have found literally trillions of articles which 1) describe floating point numbers and then 2) talk about being careful with excel because of floating point numbers. I have not found a single statement saying "all types are 64 bit floating point numbers except text". I have not found a single statement which says "changing the type of a cell only changes its visual representation and not its internal representation, unless you change the type from text to some other type which is not text or you change some other type which is not text to text". This is literally all I want to know, and it's so simple and axiomatic that I am amazed that I can find trillions of articles and pages which talk around these statements but do not state them directly.

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• Why are my connections not closed even if I explicitly dispose of the DataContext?

  - by Chris Simpson

  I encapsulate my linq to sql calls in a repository class which is instantiated in the constructor of my overloaded controller. The constructor of my repository class creates the data context so that for the life of the page load, only one data context is used. In my destructor of the repository class I explicitly call the dispose of the DataContext though I do not believe this is necessary. Using performance monitor, if I watch my User Connections count and repeatedly load a page, the number increases once per page load. Connections do not get closed or reused (for about 20 minutes). I tried putting Pooling=false in my config to see if this had any effect but it did not. In any case with pooling I wouldn't expect a new connection for every load, I would expect it to reuse connections. I've tried putting a break point in the destructor to make sure the dispose is being hit and sure enough it is. So what's happening? Some code to illustrate what I said above: The controller: public class MyController : Controller { protected MyRepository rep; public MyController () { rep = new MyRepository(); } } The repository: public class MyRepository { protected MyDataContext dc; public MyRepository() { dc = getDC(); } ~MyRepository() { if (dc != null) { //if (dc.Connection.State != System.Data.ConnectionState.Closed) //{ // dc.Connection.Close(); //} dc.Dispose(); } } // etc } Note: I add a number of hints and context information to the DC for auditing purposes. This is essentially why I want one connection per page load

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• Retaining parameters in ASP.NET MVC

  - by MapDot

  Many MVC frameworks (e.g. PHP's Zend Framework) have a way of providing basic state management through URLs. The basic principle is this: Any parameters that were not explicitly modified or un-set get copied into every URL For instance, consider a listing with pagination. You'll have the order, direction and page number passed as URL parameters. You may also have a couple of filters. Changing the value of a filter should not alter the sort order. ASP.net MVC seems to remember your controller and action by default: <%: Html.RouteLink("Next", "MyRoute", new {id = next.ItemId}) %> This will not re-set your action or controller. However, it does seem to forget all other parameters. The same is true of ActionLink. Parameters that get set earlier on in your URL seem to get retained as well. Is there a way to make it retain more than that? For instance, this does not seem to affect any of the links being generated: RouteValues.RouteData.Values["showDeleted"] = true;

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• TicTacToe strategic reduction

  - by NickLarsen

  I decided to write a small program that solves TicTacToe in order to try out the effect of some pruning techniques on a trivial game. The full game tree using minimax to solve it only ends up with 549,946 possible games. With alpha-beta pruning, the number of states required to evaluate was reduced to 18,297. Then I applied a transposition table that brings the number down to 2,592. Now I want to see how low that number can go. The next enhancement I want to apply is a strategic reduction. The basic idea is to combine states that have equivalent strategic value. For instance, on the first move, if X plays first, there is nothing strategically different (assuming your opponent plays optimally) about choosing one corner instead of another. In the same situation, the same is true of the center of the walls of the board, and the center is also significant. By reducing to significant states only, you end up with only 3 states for evaluation on the first move instead of 9. This technique should be very useful since it prunes states near the top of the game tree. This idea came from the GameShrink method created by a group at CMU, only I am trying to avoid writing the general form, and just doing what is needed to apply the technique to TicTacToe. In order to achieve this, I modified my hash function (for the transposition table) to enumerate all strategically equivalent positions (using rotation and flipping functions), and to only return the lowest of the values for each board. Unfortunately now my program thinks X can force a win in 5 moves from an empty board when going first. After a long debugging session, it became apparent to me the program was always returning the move for the lowest strategically significant move (I store the last move in the transposition table as part of my state). Is there a better way I can go about adding this feature, or a simple method for determining the correct move applicable to the current situation with what I have already done?

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• What can i use to journal writes to file system

  - by Dmitry

  Hello, all I need to track all writes to files in order to have synchronized version of files on different place (server or just other directory, not considerable). Let it: all files located in same directory feel free to create some system files (e.g. SomeFileName.Ext~temp-data) no one have concurrent access to synced directory; nobody spoil ours meta-files or change real-files before we do postponed writes (like a commits) do not to care recovering "local" changes in case of crash; system can just rolled back to state of "server" by simple copy from it significant to have it transparent to use (so programmer must just call ordinary fopen(), read(), write()) It must be guaranteed that copy of files which "server" have is consistent. That is whole files scope existed in some moment of time. They may be sufficiently outdated but it must be fair snapshot of all files at some time. As i understand i should overload writing logic to collect data in order sent changes to "server". For example writing to temporary File~tmp. And so i have to overload reads in order program could read actual data of file. It would be great if you suggest some existing library (java or c++, it is unimportant) or solution (VCS customizing?). Or give hints how should i write it by myself. edit: After some reading i have more precision requirements: I need COW (Copy-on-write) wrapper for fopen(),fwrite(),.. or interceptor (hook) WriteFile() and other FS api system calls. Log-structured file system in userspace would be a alternative too.

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• Unmanaged Process in Mono

  - by Residuum

  I want to start a quite expensive process (jackd) from a Mono application, and do not need full access to the process from the application itself. As the process is so expensive in terms of CPU usage, a Glib.IdleHandler for polling the process will not work, as it is never executed, and the GUI becomes unresponsive. Is there any way to have the cake and eating it at the same time in Mono? EDIT: I only need to be able to start and stop the process from Mono, I do not need information about the state of the process or if it has exited, as my application will register itself as a client to jackd, basically I need a "replacement" for bash's jackd &>/dev/null 2>&1 & for the System.Diagnostics.Process ;). Here is what I have so far for starting and stopping the process: public void StartJackd() { _jackd = new Process (); _jackd.StartInfo = _jackdStartup; if (_jackd.Start ()) { _jackd.EnableRaisingEvents = true; _jackd.Exited += JackdExited; } } public void StopJackd() { if (_jackd != null && !_jackd.HasExited) { _jackd.CloseMainWindow (); } } And somewhere else I have this code for registering the IdleHandler: GLib.Idle.Add(new GLib.IdleHandler(UpdateJackdConnections)); This handler will fire all the time, while the process is not running, but never, when jackd is running.

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• one two-directed tcp socket of two one-directed? (linux, high volume, low latency)

  - by osgx

  Hello I need to send (interchange) a high volume of data periodically with the lowest possible latency between 2 machines. The network is rather fast (e.g. 1Gbit or even 2G+). Os is linux. Is it be faster with using 1 tcp socket (for send and recv) or with using 2 uni-directed tcp sockets? The test for this task is very like NetPIPE network benchmark - measure latency and bandwidth for sizes from 2^1 up to 2^13 bytes, each size sent and received 3 times at least (in teal task the number of sends is greater. both processes will be sending and receiving, like ping-pong maybe). The benefit of 2 uni-directed connections come from linux: http://lxr.linux.no/linux+v2.6.18/net/ipv4/tcp_input.c#L3847 3847/* 3848 * TCP receive function for the ESTABLISHED state. 3849 * 3850 * It is split into a fast path and a slow path. The fast path is 3851 * disabled when: ... 3859 * - Data is sent in both directions. Fast path only supports pure senders 3860 * or pure receivers (this means either the sequence number or the ack 3861 * value must stay constant) ... 3863 * 3864 * When these conditions are not satisfied it drops into a standard 3865 * receive procedure patterned after RFC793 to handle all cases. 3866 * The first three cases are guaranteed by proper pred_flags setting, 3867 * the rest is checked inline. Fast processing is turned on in 3868 * tcp_data_queue when everything is OK. All other conditions for disabling fast path is false. And only not-unidirected socket stops kernel from fastpath in receive

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• Low-level Keyboard Hooks/SendInput with Winkey+L possible? (workstation lockout is intercepted in Vi

  - by Brian Jorgensen

  I work on a project called UAWKS (Unofficial Apple Wireless Keyboard Support) that helps Windows users use Apple's bluetooth keyboard. One of the main goals of UAWKS is to swap the Cmd key (which behaves as Winkey in Windows) with Ctrl, allowing users to do Cmd+C for copy, Cmd+T for new tab, etc. It is currently developed using AutoHotkey, which worked pretty well under Windows XP. However, on Vista and Windows 7, Cmd+L causes problems: Regardless of low-level keyboard hooks, Winkey+L is always intercepted by Windows and normally locks the workstation... You can disable workstation locking with this registry hack, but pressing Winkey+L still can't be rebound in AHK Pressing Winkey+L leaves Winkey in the Keydown state until the next (additional) Winkey Up. Simulating a Keyup event doesn't seem to work either! It seems that Winkey+L is a special chord that messes everything else up. I've looked through the AHK source code, and they try to address this problem in SendKey() in keyboard_mouse.cpp (near line 883 in v1.0.48.05), but it doesn't work. I wrote up my own low-level keyboard hook application in C#, and I see the same problem. Has anyone else run into this? Is there a workaround?

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• Database schema for a library

  - by ABach

  Hi all - I'm designing a library management system for a department at my university and I wanted to enlist your eyes on my proposed schema. This post is primarily concerned with how we store multiple copies of each book; something about what I've designed rubs me the wrong way, and I'm hoping you all can point out better ways to tackle things. For dealing with users checking out books, I've devised three tables: book, customer, and book_copy. The relationships between these tables are as follows: Every book has many book_copies (to avoid duplicating the book's information while storing the fact that we have multiple copies of that book). Every user has many book_copies (the other end of the relationship) The tables themselves are designed like this: ------------------------------------------------ book ------------------------------------------------ + id + title + author + isbn + etc. ------------------------------------------------ ------------------------------------------------ customer ------------------------------------------------ + id + first_name + first_name + email + address + city + state + zip + etc. ------------------------------------------------ ------------------------------------------------ book_copy ------------------------------------------------ + id + book_id (FK to book) + customer_id (FK to customer) + checked_out + due_date + etc. ------------------------------------------------ Something about this seems incorrect (or at least inefficient to me) - the perfectionist in me feels like I'm not normalizing this data correctly. What say ye? Is there a better, more effective way to design this schema? Thanks!

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• How to Treat Race Condition of Session in Web Application?

  - by Morgan Cheng

  I was in a ASP.NET application has heavy traffic of AJAX requests. Once a user login our web application, a session is created to store information of this user's state. Currently, our solution to keep session data consistent is quite simple and brutal: each request needs to acquire a exclusive lock before being processed. This works fine for tradition web application. But, when the web application turns to support AJAX, it turns to not efficient. It is quite possible that multiple AJAX requests are sent to server at the same time without reloading the web page. If all AJAX requests are serialized by the exclusive lock, the response is not so quick. Anyway, many AJAX requests that doesn't access same session variables are blocked as well. If we don't have a exclusive lock for each requests, then we need to treat all race condition carefully to avoid dead lock. I'm afraid that would make the code complex and buggy. So, is there any best practice to keep session data consistent and keep code simple and clean?

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• Reorganizing development environment for single developer/small shop

  - by Matthew

  I have been developing for my company for approximately three years. We serve up a web portal using Microsoft .NET and MS SQL Server on DotNetNuke. I am going to leave my job full time at the end of April. I am leaving on good terms, and I really care about this company and the state of the web project. Because I haven't worked in a team environment in a long time, I have probably lost touch with what 'real' setups look like. When I leave, I predict the company will either find another developer to take over, or at least have developers work on a contractual basis. Because I have not worked with other developers, I am very concerned with leaving the company (and the developer they hire) with a jumbled mess. I'd like to believe I am a good developer and everything makes sense, but I have no way to tell. My question, is how do I set up the development environment, so the company and the next developer will have little trouble getting started? What would you as a developer like in place before working on a project you've never worked on? Here's some relevant information: There is a development server onsite and a production server offsite in a data center . There is a server where backups and source code (Sourcegear Vault) are stored. There is no formal documentation but there are comments in the code. The company budget is tight so free suggestions will help the best. I will be around after the end of April on a consulting basis so I can ask simple questions but I will not be available full time to train someone

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• _beginthreadx and socket

  - by user638197

  hi, i have a question about the _beginthreadx function In the third and fourth parameter: if i have this line to create the thread hThread=(HANDLE)_beginthreadex(0,0, &RunThread, &m_socket,CREATE_SUSPENDED,&threadID ); m_socket is the socket that i want inside the thread (fourth parameter) and i have the RunThread function (third parameter) in this way static unsigned __stdcall RunThread (void* ptr) { return 0; } It is sufficient to create the thread independently if m_socket has something or not? Thanks in advance Thank you for the response Ciaran Keating helped me understand better the thread I'll explain a little more the situation I´m creating the tread in this function inside a class public: void getClientsConnection() { numberOfClients = 1; SOCKET temporalSocket = NULL; firstClient = NULL; secondClient = NULL; while (numberOfClients < 2) { temporalSocket = SOCKET_ERROR; while (temporalSocket == SOCKET_ERROR) { temporalSocket = accept(m_socket, NULL, NULL); //----------------------------------------------- HANDLE hThread; unsigned threadID; hThread=(HANDLE)_beginthreadex(0,0, &RunThread, &m_socket,CREATE_SUSPENDED,&threadID ); WaitForSingleObject( hThread, INFINITE ); if(!hThread) printf("ERROR AL CREAR EL HILO: %ld\n", WSAGetLastError()); //----------------------------------------------- } if(firstClient == NULL) { firstClient = temporalSocket; muebleC1 = temporalSocket; actionC1 = temporalSocket; ++numberOfClients; printf("CLIENTE 1 CONECTADO\n"); } else { secondClient = temporalSocket; muebleC2 = temporalSocket; actionC2 = temporalSocket; ++numberOfClients; printf("CLIENTE 2 CONECTADO\n"); } } } What i'm trying to do is to have the socket inside the thread while wait for a client connection Is this feasible as i have the code of the thread? I can change the state of the thread that is not a problem Thanks again

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• Partial slideDown with jQuery

  - by Jon

  I have some buttons that have drawer menus and what I'd like to do is add a state so that when the user hovers over the button, the drawer bumps out slightly (maybe with a little wiggle/rubber-banding) so that they know that there's a drawer with more information. I have the sliding working and a hover function set up, but I don't know how to implement a partial slideDown. Any ideas? FIDDLE. Code: <div class="clause"> <div class="icon"><img src="http://i.imgur.com/rTu40.png"/></div> <div class="label">Location</div> <div class="info">Midwest > Indiana, Kentucky; Southwest > Texas, Nevada, Utah; Pacific > California, Hawaii</div> </div> <div class="drawer">Info 1<br/><br/></div> <div class="drawerBottom"></div> $(".clause").click(function() { var tmp = $(this).next("div.drawer"); if(tmp.is(":hidden")) tmp.slideDown('3s'); else tmp.slideUp('3s'); }); $(".clause").hover(function() { });

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• Communication between lexer and parser

  - by FredOverflow

  Every time I write a simple lexer and parser, I stumble upon the same question: how should the lexer and the parser communicate? I see four different approaches: The lexer eagerly converts the entire input string into a vector of tokens. Once this is done, the vector is fed to the parser which converts it into a tree. This is by far the simplest solution to implement, but since all tokens are stored in memory, it wastes a lot of space. Each time the lexer finds a token, it invokes a function on the parser, passing the current token. In my experience, this only works if the parser can naturally be implemented as a state machine like LALR parsers. By contrast, I don't think it would work at all for recursive descent parsers. Each time the parser needs a token, it asks the lexer for the next one. This is very easy to implement in C# due to the yield keyword, but quite hard in C++ which doesn't have it. The lexer and parser communicate through an asynchronous queue. This is commonly known under the title "producer/consumer", and it should simplify the communication between the lexer and the parser a lot. Does it also outperform the other solutions on multicores? Or is lexing too trivial? Is my analysis sound? Are there other approaches I haven't thought of? What is used in real-world compilers? It would be really cool if compiler writers like Eric Lippert could shed some light on this issue.

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• Best implementation of Java Queue?

  - by Georges Oates Larsen

  I am working (In java) on a recursive image processing algorithm that recursively traverses the pixels of the image, outward from a center point. Unfortunately... That causes stack overflows, so I have decided to switch to a Queue-based algorithm. Now, this is all fine and dandy -- But considering the fact that its queue will be analyzing THOUSANDS of pixels in a very short amount of time, while constantly popping and pushing, WITHOUT maintaining a predictable state (It could be anywhere between length 100, and 20000); The queue implementation needs to have significantly fast popping and pushing abilities. A linked list seems attractive due to its ability to push elements unto its self without rearranging anything else in the list, but in order for it to be fast enough, it would need easy access to both its head, AND its tail (or second-to-last node if it were not doubly-linked). Sadly, though I cannot find any information related to the underlying implementation of linked lists in Java, so it's hard to say if a linked list is really the way to go... This brings me to my question... What would be the best implementation of the Queue interface in Java for what I intend to do? (I do not wish to edit or even access anything other than the head and tail of the queue -- I do not wish to do any sort of rearranging, or anything. On the flip side, I DO intend to do a lot of pushing and popping, and the queue will be changing size quite a bit, so preallocating would be inefficient)

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• VB.NET 2008, Windows 7 and saving files

  - by James Brauman

  Hello, We have to learn VB.NET for the semester, my experience lies mainly with C# - not that this should make a difference to this particular problem. I've used just about the most simple way to save a file using the .NET framework, but Windows 7 won't let me save the file anywhere (or anywhere that I have found yet). Here is the code I am using to save a text file. Dim dialog As FolderBrowserDialog = New FolderBrowserDialog() Dim saveLocation As String = dialog.SelectedPath ... Build up output string ... Try ' Try to write the file. My.Computer.FileSystem.WriteAllText(saveLocation, output, False) Catch PermissionEx As UnauthorizedAccessException ' We do not have permissions to save in this folder. MessageBox.Show("Do not have permissions to save file to the folder specified. Please try saving somewhere different.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error) Catch Ex As Exception ' Catch any exceptions that occured when trying to write the file. MessageBox.Show("Writing the file was not successful.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error) End Try The problem is that this using this code throws an UnauthorizedAccessException no matter where I try to save the file. I've tried running the .exe file as administrator, and the IDE as administrator. Is this just Windows 7 being overprotective? And if so, what can I do to solve this problem? The requirements state that I be able to save a file! Thanks.

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• What's the best way to store Logon User information for Web Application?

  - by Morgan Cheng

  I was once in a project of web application developed on ASP.NET. For each logon user, there is an object (let's call it UserSessionObject here) created and stored in RAM. For each HTTP request of given user, matching UserSessoinObject instance is used to visit user state information and connection to database. So, this UserSessionObject is pretty important. This design brings several problems found later: 1) Since this UserSessionObject is cached in ASP.NET memory space, we have to config load balancer to be sticky connection. That is, HTTP request in single session would always be sent to one web server behind. This limit scalability and maintainability. 2) This UserSessionObject is accessed in every HTTP request. To keep the consistency, there is a exclusive lock for the UserSessionObject. Only one HTTP request can be processed at any given time because it must to obtain the lock first. The performance and response time is affected. Now, I'm wondering whether there is better design to handle such logon user case. It seems Sharing-Nothing-Architecture helps. That means long user info is retrieved from database each time. I'm afraid that would hurt performance. Is there any design pattern for long user web app? Thanks.

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• JSF 2 - clearing component attributes on page load?

  - by jamiebarrow

  Hi, The real question: Is there a way to clear certain attributes for all components on an initial page load? Background info: In my application, I have a JSF 2.0 frontend layer that speaks to a service layer (the service layer is made up of Spring beans that get injected to the managed beans). The service layer does its own validation, and I do the same validation in the frontend layer using my own validator classes to try and avoid code duplication somehow. These validator classes aren't JSF validators, they're just POJOs. I'm only doing validation on an action, so in the action method, I perform validation, and only if it's valid do I call through to the service layer. When I do my validation, I set the styleClass and title on the UIComponents using reflection (so if the UIComponent has the setStyleClass(:String) or setTitle(:String) methods, then I use them). This works nicely, and on a validation error I see a nicely styled text box with a popup containing the error message if I hover over it. However, since the component is bound to a Session Scoped Managed Bean, it seems that these attributes stick. So if I navigate away and come back to the same page, the styleClass and title are still in the error state. Is there a way to clear the styleClass and title attributes on each initial page load? Thanks, James P.S. I'm using the action method to validate because of some issues I had before with JSF 1.2 and it's validation methods, but can't remember why... so that's why I'm using the action method to validate.

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• Windows Phone - failing to get a string from a website with login information

  - by jumantyn

  I am new to accessing web services with Windows Phone 7/8. I'm using a WebClient to get a string from a php-website. The site returns a JSON string but at the moment I'm just trying to put it into a TextBox as a normal string just to test if the connection works. The php-page requires an authentication and I think that's where my code is failing. Here's my code: WebClient client = new WebClient(); client.Credentials = new NetworkCredential("myUsername", "myPassword"); client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(client_DownloadStringCompleted); client.DownloadStringAsync(new Uri("https://www.mywebsite.com/ba/php/jsonstuff.php")); void client_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e) { try { string data = e.Result; this.jsonText.Text = data; } catch (Exception ex) { System.Diagnostics.Debug.WriteLine(ex.Message); } } This returns first a WebException and then a TargetInvocationException. If I replace the Uri with for example "http://www.google.com/index.html" the jsonText TextBox gets filled with html text from Google (oddly enough, this also works even when the WebClient credentials are still set). So is the problem in the setting of the credentials? I couldn't find any good results when searching for guides on how to access php-pages with credentials, only without them. Then I found a short mention somewhere to use the WebClient.Credentials property. But should it work some other way? Update: here's what I can get out of the WebException (sorry for the bad formatting): System.Net.WebException: The remote server returned an error: NotFound. ---System.Net.WebException: The remote server returned an error: NotFound. at System.Net.Browser.ClientHttpWebRequest.InternalEndGetResponse(IAsyncResult asyncResult) at System.Net.Browser.ClientHttpWebRequest.<c_DisplayClasse.b_d(Object sendState) at System.Net.Browser.AsyncHelper.<c_DisplayClass1.b_0(Object sendState) --- End of inner exception stack trace --- at System.Net.Browser.AsyncHelper.BeginOnUI(SendOrPostCallback beginMethod, Object state) at System.Net.Browser.ClientHttpWebRequest.EndGetResponse(IAsyncResult asyncResult) at System.Net.WebClient.GetWebResponse(WebRequest request, IAsyncResult result) at System.Net.WebClient.DownloadBitsResponseCallback(IAsyncResult result)

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• jsf annotations

  - by Andrew Bucknell

  I've created an address bean and I want to use it twice - once for street address and once for mailing address. I can achieve this using faces config as per the below, but I'm wondering if I can do this via annotations. e.g. put @ManagedBean(name="StreetAddress") and @ManagedBean(name="MailingAddress") on the same class? I feel like I am missing something obvious here but I'm not sure what. <managed-bean> <managed-bean-name>MailingAddress</managed-bean-name> <managed-bean-class>com.leetb.jsf_ex1.model.AddressBean</managed-bean-class> <managed-bean-scope>session</managed-bean-scope> <map-entries/> </managed-bean> <managed-bean> <managed-bean-name>StreetAddress</managed-bean-name> <managed-bean-class>com.leetb.jsf_ex1.model.AddressBean</managed-bean-class> <managed-bean-scope>session</managed-bean-scope> <map-entries/> </managed-bean> public class AddressBean { private String line_one; private String line_two; private String suburb; private String state; private String postcode; /* getters and setters snipped */ }

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