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• How can I get a list of modified records from a SQL Server database?

  - by Pixelfish

  I am currently in the process of revamping my company's management system to run a little more lean in terms of network traffic. Right now I'm trying to figure out an effective way to query only the records that have been modified (by any user) since the last time I asked. When the application starts it loads the job information and caches it locally like the following: SELECT * FROM jobs. I am writing out the date/time a record was modified ala UPDATE jobs SET Widgets=@Widgets, LastModified=GetDate() WHERE JobID=@JobID. When any user requests the list of jobs I query all records that have been modified since the last time I requested the list like the following: SELECT * FROM jobs WHERE LastModified>=@LastRequested and store the date/time of the request to pass in as @LastRequest when the user asks again. In theory this will return only the records that have been modified since the last request. The issue I'm running into is when the user's date/time is not quite in sync with the server's date/time and also of server load when querying an un-indexed date/time column. Is there a more effective system then querying date/time information?

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• Button inside a repeater with dropdownlist

  - by TheAlbear

  I have a repeater with a literal, a dropdown list, and a button. <asp:Repeater ID="Repeater1" runat="server" OnItemDataBound="rep_ItemDataBound" onitemcommand="Repeater1_ItemCommand"> <ItemTemplate> <div class="buypanel"> <ul> <li>Choose finish <asp:DropDownList ID="ddlFinish" runat="server"></asp:DropDownList></li> <li>Qty <asp:Literal ID="ltQty" runat="server"></asp:Literal></li> <li><asp:Button ID="butBuy" runat="server" Text="Button" /></li> </ul> </div> </ItemTemplate> </asp:Repeater> I am binding all the information in the code behind like protected void rep_ItemDataBound(object sender, RepeaterItemEventArgs e) { if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem) { Products product = (Products) e.Item.DataItem; //Dropdownlist to be bound. //Set Buy Button var butBuy = (Button) e.Item.FindControl("butBuy"); butBuy.CommandName = "Buy"; butBuy.CommandArgument = product.Id.ToString(); } } and i have my itemcommand to pick up on the button click protected void Repeater1_ItemCommand(object source, RepeaterCommandEventArgs e) { if(e.CommandName == "Buy") { } } I am not sure how, with a given button click, to pickup the right information from the text box and dropdown list which is along side it?

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• own drawImage / drawLine in OpenGL

  - by Chrise

  I'm implementing some native 2D-draw functions in my graphics engine for android, but now there's another question coming up, when I observe the performance of my program. At the moment I'm implementing a drawLine/drawImage function. In summary, there are following different values for drawing each different line / image: the color the alpha value the width of the line rotation (only for images) size/scale (also for images) blending method (subrtract, add, normal-alpha) Now, when an imageLine is drawn, I put the CPU-calculated vertex-positions and uv-values for 6 vertices (2 triangles), into a Floatbuffer and draw it immediately with drawArrays, after passing information for drawing (color,alpha, etc.) via uniforms to the shader. When I draw an image, the pre-set VBO is directly drawn after passing information. The first fact I recognized, is: of course drawing Images is much faster, than imagelines (beacuse of VBOs), but also: I cannot pre-put vertex-data into a VBO for imageLines, because imageLines have no static shape like normal images (varying linelength, varying linewidth and the vertex positions of x1,y1 and x2,y2 change too often) That's why I use a normal Floatbuffer, instead of a VBO. So my question is: What's the best way for managing images, and other 2D-graphics functions. For me it's some kind of important, that the user of the engine is able to draw as many images/2D graphics as possible, without loosing to much performance. You can find the functions for drawing images, imagelines, rects, quads, etc. here: https://github.com/Chrise55/LLama3D/blob/master/Llama3DLibrary/src/com/llama3d/object/graphics/image/ImageBase.java Here an example how it looks with many images (testing artificial neural networks), it works fine, but already little bit slow with that many images... :(

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• New to JEE; architecture suggestions for a service/daemon?

  - by Kate

  I am brand new to the JEE world. As an exercise to try and familiarize myself with JEE, I'm trying to create a tiered web-app, but I'm getting a little stuck on what the best way is to spin up a service in the background that does work. Parameters of the service: It must open and hold a socket connection and receive information from the connected server. There is a 1-to-1 correlation between a user and a new socket connection. So the idea is the user presses a button on the web-page, and somewhere on the server a socket connection is opened. For the remainder of the users session (or until the user presses some sort of disconnect button) the socket remains open and pushes received information to some sort of centralized store that servlets can query and return to the user via AJAX. Is there a JEE type way to handle this situation? Naturally what I would think to do is to just write a Java application that listens on a port that the servlets can connect to and spawns new threads that open these sockets, but that seems very ad-hoc to me. (PS: I am also new to Stack Overflow, so forgive me if it takes me some time to figure the site out!)

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• Modeling Buyers & Sellers in a Rails Ecommerce App

  - by MikeH

  I'm building a Rails app that has Etsy.com style functionality. In other words, it's like a mall. There are many buyers and many sellers. I'm torn about how to model the sellers. Key facts: There won't be many sellers. Perhaps less than 20 sellers in total. There will be many buyers. Hopefully many thousands :) I already have a standard user model in place with account creation and roles. I've created a 'role' of 'seller', which the admin will manually apply to the proper users. Since we'll have very few sellers, this is not an issue. I'm considering two approaches: (1) Create a 'store' model, which will contain all the relevant store information. Products would :belong_to :store, rather than belonging to the seller. The relationship between the user and store models would be: user :has_one store. My main problem with this is that I've always found has_one associations to be a little funky, and I usually try to avoid them. The app is fairly complex, and I'm worried about running into a cascade of problems connected to the has_one association as I get further along into development. (2) Simply include the relevant 'store' information as part of the user model. But in this case, the store-related db columns would only apply to a very small percentage of users since very few users will also be sellers. I'm not sure if this is a valid concern or not. It's very possible that I'm thinking about this incorrectly. I appreciate any thoughts. Thanks.

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• What are the first steps in C#/.NET development?

  - by paxdiablo

  Okay, I'm biting the bullet and deciding to get into the whole Microsoft/C#/.NET culture and I'm going to do this by putting together a simple (hah!) application. It will basically be an application in which I want to store images and associate with them other optional things. It must be able to import images from the filesystem (and hopefully camera/scanner) then allow the user to add text, audio and other information. I plan to store the images and auxillary information into a database. What the application will do with said data isn't important (yet). Keep in mind I know absolutely nothing about C# or .NET although, as an old codger, I know a great deal about many other things and will regale you with stories and anecdotes until you quietly slip away :-) What are the first steps to take in developing such an application? I've already set out UI layouts and likely process flows although it may be that the development environment dictates changes. Development environment is currently XP SP3 + VS2008 (though I can upgrade if absolutely necessary). What should I be looking at as the first step? Are there any gotchas I should be looking out for?

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• Serializing an extended form object

  - by andyperfect

  I've been reading up on this whole subject, but I never came across this specific problem. I already understand that the whole idea of serializing an entire form is a horrible idea and just doesn't work. But, I am encountering a bit of a different problem. I have a class that inherits the "button" form object, that I call DataButton. Now for my problem. I want to be able to serialize this class, but I don't need any of the information from the actual button class. Is there any way to bypass the fact that I can't set the button form object to Serializable() and notify VB that when serialization is to occur, it should simply skip over that information? Theoretically, if such a procedure were possible, I'd be able to do the entire serialization without a hitch. I came up with the idea earlier of removing the "inherits" feature from the class, and having simply a button within the class, but that makes my program really difficult to work with as I am constantly changing the location, size, backgroundImage, text, and whatnot. Thus, immediate updates would be much tougher to work with. Any help would be greatly appreciated.

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• 2d Game Making > Where can someone get Free Tilesets?

  - by Iscariot

  I have been scouring the internet for free tilesets that are open to you. I have found http://lostgarden.com/ It does not seem very useful. There are a few things here and there, but overall not much to really make a game off of. http://www.flyingyogi.com/fun/spritelib.html Spritelib is a little better it has some useful information, but is still the graphics are more in the 8bit variety. http://reinerstileset.4players.de/ This is heavily stylized and its hard to have this match with any other free tile-sets available. All other sites I have found have just been rips from games and those are protected by a copyright and remain unusable. Right now I need simple objects to build the inside of buildings, but I have seem to have come up short in that area. I have plenty of things for outside of buildings, but nothing for in. I am hoping someone else has had this problem and has found a solution. If not, I hope the information I have provided can help someone else in their conquest.

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• formmail to email in database

  - by aarontb

  Here's what I need to setup...and I am not well versed in PHP/SQL...but this is what I'm trying to do. On the New User database, I will have a section where they can have information sent to their phone using the provider's default e-mail to text msg (i.e. [email protected].) New User: Input number: ______________(2225551212 format, no hyphens, etc.) Select Provider: (Drop-down menu with proper @provider.ext...) Then the formmail, when sent, if for specific user will get ($phone".@."$provider); or something like that and send a preset message like: $user."requested information on ".$product."on".$date." at ".$time."."; Is this possible? The $user, $product, $date, $time all are generated directly from the most recent input page for a database. Is this possible? Please help!

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• MSSQL Server using multiple ID Numbers

  - by vincer

  I have an web application that creates printable forms, these forms have a unique number on them, the problem is I have 2 forms that separate numbers need to be created for them. ie) Form1- Numbered 2000000-2999999 Form2- Numbered 3000000-3999999 dbo.test2 - is my form information table Tsel - is my autoinc table for the 3000000 series numbers Tadv - is my autoinc table for the 2000000 series numbers What I have done is create 2 tables with just autoinc row (one for 2000000 series numbers and one for 3000000 series numbers), I then created a trigger to add a record to the coresponding table, read back the autoinc number and add it to my table that stores the form information including the just created autoinc number for the right series of forms. Although it does work, I'm concerned that the numbers will get messed up under load. I'm not sure the @@IDENTITY will always return the right value when many people are using the system. (I cannot have duplicates and I need to use the numbering form show above. Thanks for any help See code below. ** TRIGGER ** CREATE TRIGGER MAKEANID2 ON dbo.test2 AFTER INSERT AS SET NOCOUNT ON declare @someid int declare @someid2 int declare @startfrom int declare @test1 varchar(10) select @someid=@@IDENTITY select @test1 = (Select name1 from test2 where sysid = @someid ) if @test1 = 'select' begin insert into Tsel Default values select @someid2 = @@IDENTITY end if @test1 = 'adv' begin insert into Tadv Default values select @someid2 = @@IDENTITY end update test2 set name2=(@someid2) where sysid = @someid SET NOCOUNT OFF

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• ASP.NET Custom Control - Template Allowing Literal Content

  - by Bob Fincheimer

  I want my User Control to be able to have Literal Content inside of it. For Example: <fc:Text runat="server">Please enter your login information:</fc:Text> Currently the code for my user control is: <ParseChildren(True, "Content")> _ Partial Public Class ctrFormText Inherits FormControl Private _content As ArrayList <PersistenceMode(PersistenceMode.InnerDefaultProperty), _ DesignerSerializationVisibility(DesignerSerializationVisibility.Content), _ TemplateInstance(TemplateInstance.Single)> _ Public Property Content() As ArrayList Get If _content Is Nothing Then Return New ArrayList End If Return _content End Get Set(ByVal value As ArrayList) _content = value End Set End Property Protected Overrides Sub CreateChildControls() If _content IsNot Nothing Then ctrChildren.Controls.Clear() For Each i As Control In _content ctrChildren.Controls.Add(i) Next End If MyBase.CreateChildControls() End Sub End Class And when I put text inside this control (like above) i get this error: Parser Error Message: Literal content ('Please enter your login information to access CKMS:') is not allowed within a 'System.Collections.ArrayList'. This control could have other content than just the text, so making the Content property an attribute will not solve my problem. I found in some places that I need to implement a ControlBuilder Class, along with another class that implements IParserAccessor. Anyway I just want my default "Content" property to have all types of controls allowed in it, both literal and actual controls.

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• XML Serialization : Has property of type Class1 : Class1 has another property : How to write the property of Class1 into XML?

  - by Wonderlander

  I want to serialize a class. In this class there's a property, type of Class1, while there are other properties in Class1. public abstract class ComponentBase { [ToSerialize]//An attribute defined my me, indicating whether or not to serialize this property. public ComponentArgs Parameters { get; set; } } public class ComponentArgs { public string WorkingPath { get; set; } public IList<Language> Languages { get; set; } public string ComponentOutputPath { get; set; } } The information serialized must be put into a Dictionary, such as ComponentSettings[str_Name]=str_Value. The method used in reading this value is Reflection. pinfo: Property Info got via Type.GetProperties(); componentSettings.Add(pinfo.Name, pinfo.GetValue((object)this, null).ToString()); The information after serialization is: <Parameters>MS.STBIntl.Pippin.Framework.ComponentArgs</Parameters> instead of the value of ComponentArgs.WorkingPath. The solution I thought of is to append to the following line an if judgement: componentSettings.Add(pinfo.Name, pinfo.GetValue((object)this, null).ToString()); if(pinfo is ComponentArgs) componentSettings.Add(pinfo.Name, pinfo.GetValue( (ComponentArgs)this, null).WorkingPath+"\n"+ LanguageList+"\n"+ //Language list is a concatinated string of all elements in the list. (ComponentArgs)this, null).ComponentOutputPath+"\n"+ ); When deserializing, add a judgement of whether the value contains more than 2 "\n", if so, extract each value from the string. But this way seems clumsy and much more like an workaround. I wonder if there's any more professional way of doing it? My reviewer is very particular and he won't accept such a solution. If you know a way, could you please share it with me? Thanks a lot.

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• Best way and problems when using ajax tabs with an MVC PHP project

  - by Jonathan

  Hi, I'm building an IMDB.com like website using PHP/jQuery and a MVC approach (no OOP). I have an index.php base controller to 'rule them all' :), a controllers folder with all the controllers, a models folder and a view folder. In some pages of the website I have tabbed navigation, when the visitor clicks on one of those tabs to get more information, jQuery gets that data using the $.post or $.get method and shows it on the tab container, obviously without refreshing the page. The problem is that those pages loaded by ajax are also generated using controllers, models, and views, and the things are getting a bit complicated for someone like me ( = 'no experience'). To dynamically get the data I some times need to include a model twice, include an include in an include in an include, send information multiple times, connect with the database again, and all sort of things like that and I'm sure there is a better and prettier way to do this. I'm searching for the best approach and common methods for this. I have no experience working with a big project like this. This is a personal project so I have full control and every answer is welcome. Thanks!!!

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• possible to make codeigniter work with another framework?

  - by ajsie

  the situation is this. my client (who also is a programmer) asks me to develop an address book (with mysql database) with a lot of functions. then he can interact with some class methods i provide for him. kinda like an API. the situation is that the address book application is getting bigger and bigger, and i feel like its way better to use CodeIgniter to code it with MVC. i wonder if i can use codeigniter, then in some way give him the access to controller methods. eg. in a controller there are some functions u can call with the web browser. public function create_contact($information) {..} public function delete_contact($id) {..} public function get_contact($id) {..} however, these are just callable from web browser. how can i let my client have access to these functions like an API? then in his own application he can use: $result = $address_book-create_contact($information); if($result) { echo "Success"; } $contact = $address_book-get_contact($id); is this possible? cause i just know how to access the controller methods with the webbrowser. and i guess its not an option for him to use header(location) to access them. all suggestions to make this possible are welcomed! thanks

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• .NET memory leak?

  - by SA

  I have an MDI which has a child form. The child form has a DataGridView in it. I load huge amount of data in the datagrid view. When I close the child form the disposing method is called in which I dispose the datagridview this.dataGrid.Dispose(); this.dataGrid = null; When I close the form the memory doesn't go down. I use the .NET memory profiler to track the memory usage. I see that the memory usage goes high when I initially load the data grid (as expected) and then becomes constant when the loading is complete. When I close the form it still remains constant. However when I take a snapshot of the memory using the memory profiler, it goes down to what it was before loading the file. Taking memory snapshot causes it to forcefully run garbage collector. What is going on? Is there a memory leak? Or do I need to run the garbage collector forcefully? More information: When I am closing the form I no longer need the information. That is why I am not holding a reference to the data.

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• How security of the systems might be improved using database procedures?

  - by Centurion

  The usage of Oracle PL/SQL procedures for controlling access to data often emphasized in PL/SQL books and other sources as being more secure approach. I'v seen several systems where all business logic related with data is performed through packages, procedures and functions, so application code becomes quite "dumb" and is only responsible for visualization part. I even heard some devs call such approaches and driving architects as database nazi :) because all logic code resides in database. I do know about DB procedure performance benefits, but now I'm interested in a "better security" when using thick client model. I assume such design mostly used when Oracle (and maybe MS SQL Server) databases are used. I do agree such approach improves security but only if there are not much users and every system user has a database account, so we might control and monitor data access through standard database user security. However, how such approach could increase the security for an average web system where thick clients are used: for example one database user with DML grants on all tables, and other users are handled using "users" and"user_rights" tables? We could use DB procedures, save usernames into context use that for filtering but vulnerability resides at the root - if the main database account is compromised than nothing will help. Of course in a real system we might consider at least several main users (for example frontend_db_user, backend_db_user).

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• Assistance with CC Processing script

  - by JM4

  I am currently implementing a credit card processing script, most as provided by the merchant gateway. The code calls functions within a class and returns a string based on the response. The end php code I am using (details removed of course) with example information is: <?php $gw = new gwapi; $gw->setLogin("username", "password"); $gw->setBilling("John","Smith","Acme, Inc.","888","Suite 200", "Beverly Hills", "CA","77777","US","555-555-5555","555-555-5556","[email protected]", "www.example.com"); // "CA","90210","US","[email protected]"); $gw->setOrder("1234","Big Order",1, 2, "PO1234","65.192.14.10"); $r = $gw->doSale("1.00","4111111111111111","1010"); print $gw->responses['responsetext']; ?> where setlogin allows me to login, setbilling takes the sample consumer information, set order takes the order id and description, dosale takes the amount charged, cc number and exp date. when all the variables are sent validated then sent off for processing, a string is returned in the following format: response=1&responsetext=SUCCESS&authcode=123456&transactionid=23456&avsresponse=M&orderid=&type=sale&response_code=100 where: response = transaction approved or declined response text = textual response authcode = transaction authorization code transactionid = payment gateway tran id avsresponse = avs response code orderid = original order id passed in tran request response_code = numeric mapping of processor response I am trying to solve for the following: How do I take the data which is passed back and display it appropriately on the page - If the transaction failed or AVS code doesnt match my liking or something is wrong, an error is displayed to the consumer; if the transaction processed, they are taken to a completion page and the transaction id is sent in SESSION as output to the consumer If the response_code value matches a table of values, certain actions are taken, i.e. if code =100, take to success page, if code = 300 print specific error on original page to customer, etc.

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• [java] tcp socket communication [send and recieve help]

  - by raven

  hello, I am creating a Chat in java. I have a method (onMouseRelease) inside an object that creates a tcp server and waits for a socket ServerSocket server = new ServerSocket(port); Socket channel = server.accept(); now I want to make a thread that will loop and read data from the socket, so that once the user on the other side sent me a string, I will extract the data from the socket [or is it called packet? sry I am new to this], and update a textbox to add the additional string from the socket [or packet?]. I have no idea how to READ (extract) the information from the scoket [/packet] and then update it into a JTextArea which is called userOutput. And how to Send a string to the other client, so that it will also could read the new data and update its JTextArea. (from what I know, for a 2 sided tcp communication you need one computer to host a server and the other to connect [as a client] and once the connection is set the client can also recieve new information from the socket. Is that true? and please tell me how ) Any help appreciated !! I know this is abit long but I have searched allot and didn't understand [I saw something like printwriter but failed to understand].

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• What are your best practices for ensuring the correctness of the reports from SQL?

  - by snezmqd4

  Part of my work involves creating reports and data from SQL Server to be used as information for decision. The majority of the data is aggregated, like inventory, sales and costs totals from departments, and other dimensions. When I am creating the reports, and more specifically, I am developing the SELECTs to extract the aggregated data from the OLTP database, I worry about mistaking a JOIN or a GROUP BY, for example, returning incorrect results. I try to use some "best practices" to prevent me for "generating" wrong numbers: When creating an aggregated data set, always explode this data set without the aggregation and look for any obvious error. Export the exploded data set to Excel and compare the SUM(), AVG(), etc, from SQL Server and Excel. Involve the people who would use the information and ask for some validation (ask people to help to identify mistakes on the numbers). Never deploy those things in the afternoon - when possible, try to take a look at the T-SQL on the next morning with a refreshed mind. I had many bugs corrected using this simple procedure. Even with those procedures, I always worry about the numbers. What are your best practices for ensuring the correctness of the reports?

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• New to J2EE; architecture suggestions for a service/daemon?

  - by Kate

  I am brand new to the J2EE world. As an exercise to try and familiarize myself with J2EE, I'm trying to create a tiered web-app, but I'm getting a little stuck on what the best way is to spin up a service in the background that does work. Paramters of the service: It must open and hold a socket connection and receive information from the connected server. There is a 1-to-1 correlation between a user and a new socket connection. So the idea is the user presses a button on the web-page, and somewhere on the server a socket connection is opened. For the remainder of the users session (or until the user presses some sort of disconnect button) the socket remains open and pushes received information to some sort of centralized store that servlets can query and return to the user via AJAX. Is there a J2EE type way to handle this situation? Naturally what I would think to do is to just write a Java application that listens on a port that the servlets can connect to and spawns new threads that open these sockets, but that seems very ad-hoc to me. (PS: I am also new to Stack Overflow, so forgive me if it takes me some time to figure the site out!)

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• Javascript - Wait for function to return

  - by LoadData

  So, I am working on a project which requires me to call upon a function to get data from an external source. The issue I am having, I call upon the function - However the code after the function call is continuing before the function has returned a value. Here is the function - function getData() { var myVar; var xmlLoc = $.get("http://ec.urbentom.co.uk/StudentAppData.xml", function(data) { $xml = $(data); myVar = $xml; console.log(myVar); console.log(String($xml)); localStorage.setItem("Data", $xml); console.log(String(localStorage.getItem("Data"))); return myVar; }); return myVar; console.log("Does this continue"); } And here is where it is called upon - $(document).on("pageshow","#Information",function() { $xml = $(getData()); //Here is the function call console.log($xml); //However, it will instantly go to this line before 'getData' has returned a value. $xml.find('AllData').each(function() { $(this).find('item').each(function() { if ($(this).find('Category').text()=="Facilities") { console.log($(this).find('Title').text()); //Do stuff here } else if ($(this).find('Category').text()=="Contacts" || $(this).find('Category').text()=="Information") { console.log($(this).find('Title').text()); //Do stuff here too } }); $('#informationList').html(output).listview().listview("refresh"); console.log("Finished"); }); }); Right now, I'm unsure of why it is not working. My guess is that it is because I am calling a function within a function. Does anyone have any ideas on how this issue can be fixed?

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• TCP socket communication

  - by raven

  hello, I am creating a Chat in java. I have a method (onMouseRelease) inside an object that creates a tcp server and waits for a socket like this: ServerSocket server = new ServerSocket(port); Socket channel = server.accept(); Now I want to make a thread that will loop and read data from the socket, so that once the user on the other side sends me a string, I will extract the data from the socket (or is it called packet? Sorry, I am new to this) and update a textbox to add the additional string from the socket (or packet?). I have no idea how to READ (extract) the information from the socket(/packet) and then update it into a JTextArea which is called userOutput. And how to send a string to the other client, so that it will also could read the new data and update its JTextArea. From what I know, for a 2 sided TCP communication you need one computer to host a server and the other to connect (as a client) and once the connection is set the client can also receive new information from the socket. Is that true? and please tell me how. Any help is appreciated! I know this is a bit long but I have searched a lot and didn't understand it (I saw something like PrintWriter but failed to understand).

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• Chat app vs REST app - use a thread in an Activity or a thread in a Service?

  - by synic

  In Virgil Dobjanschi's talk, "Developing Android REST client applications" (link here), he said a few things that took me by surprise. Including: Don't run http queries in threads spawned by your activities. Instead, communicate with a service to do them, and store the information in a ContentProvider. Use a ContentObserver to be notified of changes. Always perform long running tasks in a Service, never in your Activity. Stop your Service when you're done with it. I understand that he was talking about a REST API, but I'm trying to make it fit with some other ideas I've had for apps. One of APIs I've been using uses long-polling for their chat interface. There is a loop http queries, most of which will time out. This means that, as long as the app hasn't been killed by the OS, or the user hasn't specifically turned off the chat feature, I'll never be done with the Service, and it will stay open forever. This seems less than optimal. Long question short: For a chat application that uses long polling to simulate push and immediate response, is it still best practice to use a Service to perform the HTTP queries, and store the information in a ContentProvider?

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• Customer wants some data to appear after you later delete rows. System giant / not my creation. Fast

  - by John Sullivan

  This is a fairly common problem, it probably has a name, I just don't know what it is. A.) User sees obscure piece of information in Row B of L_OBSCURE_INFO displayed on some screen at a certain point. It is in table L_Obscure_info. B.) Under certain circumstances we want to correctly delete data in L_OBSCURE_INFO. Unfortunately, nobody accounted for the fact that the user might want to backtrack and see some random piece of information that was most recently in L_OBSCURE_INFO. C.) The system is enormous and L_OBSCURE_INFO is used all the time. You have no idea what the ramifications are of implementing some kind of hack and whatever you do, you don't want to introduce more bugs. I think the best approach would be to create an L_OBSCURE_INFO_HISTORY table and record a record in there every time you change data. But god help your ensuring it's accurate in this system where L_OBSCURE_INFO is being touched everywhere and you don't have time to implement L_OBSCURE_INFO_HISTORY. Is there a particularly easy, clever design solution for this kind of problem -- basically an elegant database hack? If not, is this kind of design problem under a particular class of problems or have a name?

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• On-Demand Python Thread Start/Join Freezing Up from wxPython GUI

  - by HokieTux

  I'm attempting to build a very simple wxPython GUI that monitors and displays external data. There is a button that turns the monitoring on/off. When monitoring is turned on, the GUI updates a couple of wx StaticLabels with real-time data. When monitoring is turned off, the GUI idles. The way I tried to build it was with a fairly simple Python Thread layout. When the 'Start Monitoring' button is clicked, the program spawns a thread that updates the labels with real-time information. When the 'Stop Monitoring' button is clicked, thread.join() is called, and it should stop. The start function works and the real-time data updating works great, but when I click 'Stop', the whole program freezes. I'm running this on Windows 7 64-bit, so I get the usual "This Program has Stopped Responding" Windows dialog. Here is the relevant code: class MonGUI(wx.Panel): def __init__(self, parent): wx.Panel.__init__(self, parent) ... ... other code for the GUI here ... ... # Create the thread that will update the VFO information self.monThread = Thread(None, target=self.monThreadWork) self.monThread.daemon = True self.runThread = False def monThreadWork(self): while self.runThread: ... ... Update the StaticLabels with info ... (This part working) ... # Turn monitoring on/off when the button is pressed. def OnClick(self, event): if self.isMonitoring: self.button.SetLabel("Start Monitoring") self.isMonitoring = False self.runThread = False self.monThread.join() else: self.button.SetLabel("Stop Monitoring") self.isMonitoring = True # Start the monitor thread! self.runThread = True self.monThread.start() I'm sure there is a better way to do this, but I'm fairly new to GUI programming and Python threads, and this was the first thing I came up with. So, why does clicking the button to stop the thread make the whole thing freeze up?

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