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  • Java File Handling, what did I do wrong?

    - by Urda
    Wrote up a basic file handler for a Java Homework assignment, and when I got the assignment back I had some notes about failing to catch a few instances: Buffer from file could have been null. File was not found File stream wasn't closed Here is the block of code that is used for opening a file: /** * Create a Filestream, Buffer, and a String to store the Buffer. */ FileInputStream fin = null; BufferedReader buffRead = null; String loadedString = null; /** Try to open the file from user input */ try { fin = new FileInputStream(programPath + fileToParse); buffRead = new BufferedReader(new InputStreamReader(fin)); loadedString = buffRead.readLine(); fin.close(); } /** Catch the error if we can't open the file */ catch(IOException e) { System.err.println("CRITICAL: Unable to open text file!"); System.err.println("Exiting!"); System.exit(-1); } The one comment I had from him was that fin.close(); needed to be in a finally block, which I did not have at all. But I thought that the way I have created the try/catch it would have prevented an issue with the file not opening. Let me be clear on a few things: This is not for a current assignment (not trying to get someone to do my own work), I have already created my project and have been graded on it. I did not fully understand my Professor's reasoning myself. Finally, I do not have a lot of Java experience, so I was a little confused why my catch wasn't good enough.

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  • Basic Python: Exception raising and local variable scope / binding

    - by SuperJdynamite
    I have a basic "best practices" Python question. I see that there are already StackOverflow answers tangentially related to this question but they're mired in complicated examples or involve multiple factors. Given this code: #!/usr/bin/python def test_function(): try: a = str(5) raise b = str(6) except: print b test_function() what is the best way to avoid the inevitable "UnboundLocalError: local variable 'b' referenced before assignment" that I'm going to get in the exception handler? Does python have an elegant way to handle this? If not, what about an inelegant way? In a complicated function I'd prefer to avoid testing the existence of every local variable before I, for example, printed debug information about them.

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  • unhandled errors in php

    - by lexus
    How can I know during runtime that my code threw a Warning? example try { echo (25/0); } catch (exception $exc) { echo "exception catched"; } throws a "Warning: Division by zero" error that i can not handle on my code.

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  • Browser not handling exception from AJAX panel, ASP.NET c#

    - by Grant
    Hi, i am having trouble catching errors in an AJAX panel. Even when i throw an exception in the c# code behind the front end completely ignores it. Here is the code i have setup, can anyone see why? I ideally want to show a js alert window on error. Code Behind: protected void btnX_Click(object sender, EventArgs e) { throw new ApplicationException("test"); } protected void ScriptManager_AsyncPostBackError(object sender, AsyncPostBackErrorEventArgs e) { ScriptManager.AsyncPostBackErrorMessage = e.Exception.Message; } Markup: <script type="text/javascript" language="javascript"> Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequestHandler); function EndRequestHandler(sender, e) { window.alert(e.get_error().name); } </script> <asp:ScriptManager ID="ScriptManager" runat="server" AllowCustomErrorsRedirect="true" OnAsyncPostBackError="ScriptManager_AsyncPostBackError" />

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  • Centralizing Messagebox handling for application

    - by DRapp
    I'm wondering how others deal with trying to centralize MessageBox function calling. Instead of having long text embedded all over the place in code, in the past (non .net language), I would put system and application base "messagebox" type of messages into a database file which would be "burned" into the executable, much like a resource file in .Net. When a prompting condition would arise, I would just do call something like MBAnswer = MyApplication.CallMsgBox( IDUserCantDoThat ) then check the MBAnswer upon return, such as a yes/no/cancel or whatever. In the database table, I would have things like what the messagebox title would be, the buttons that would be shown, the actual message, a special flag that automatically tacked on a subsequent standard comment like "Please contact help desk if this happens.". The function would call the messagebox with all applicable settings and just return back the answer. The big benefits of this was, one location to have all the "context" of messages, and via constants, easier to read what message was going to be presented to the user. Does anyone have a similar system in .Net to do a similar approach, or is this just a bad idea in the .Net environment.

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  • Proper exceptions to use for nulls

    - by user200295
    In the following example we have two different exceptions we want to communicate. //constructor public Main(string arg){ if(arg==null) throw new ArgumentNullException("arg"); Thing foo=GetFoo(arg); if(foo==null) throw new NullReferenceException("foo is null"); } Is this the proper approach for both exception types?

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  • Php string handling triks

    - by Dam
    Hi my question Need to get the 10 word before and 10 words after for the given text . i mean need to start the 10 words before the keyword and end with 10 word after the key word. Given text : "Twenty-three" The main trick : content having some html tags etc .. tags need to keep that tag with this content only . need to display the words from 10before - 10after content is bellow : <div id="hpFeatureBoxInt"><h3><a href="/go/homepage/i/int/news/world/1/-/news/1/hi/world/europe/8592190.stm">Suicide bombings hit Moscow Metro</a></h3><p>Past suicide bombings in Moscow have been blamed on Islamist rebels At least 35 people have been killed after two female suicide bombers blew themselves up on Moscow Metro trains in the morning rush hour,<h2><span class="dy">Top News Story</span></h2> officials say.<img height="150" width="201" alt="Emergency services carry a body from a Metro station in Moscow (29 March 2010)" src="http://wwwimg.bbc.co.uk/feedengine/homepage/images/_47550689_moscowap203_201x150.jpg">Twenty-three died in the first blast at 0756 (0356 GMT) as a<a href="#"> train stood </a>at the central Lubyanka station, beneath the offices of the FSB intelligence agency.About 40 minutes later, a second explosion ripped through a train at Park Kultury, leaving another 12 dead.No-one has said they carried out the worst attack in the capital since 2004. </p><p id="fbilisten"><a href="/go/homepage/i/int/news/heading/-/news/">More from BBC News</a></p></div> Thank you

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  • Handling very large lists of objects without paging?

    - by user246114
    Hi, I have a class which can contain many small elements in a list. Looks like: public class Farm { private ArrayList<Horse> mHorses; } just wondering what will happen if the mHorses array grew to something crazy like 15,000 elements. I'm assuming that trying to write and read this from the datastore would be crazy, because I'd get killed on the serialization process. It's important that I can get the entire array in one shot without paging, and each Horse element may only have two string properties in it, so they are pretty lightweight: public class Horse { private String mId; private String mName; } I don't need these horses indexed at all. Does it sound reasonable to just store the mHorse array as a raw Text field, and force my clients to do the deserialization? Something like: public class Farm { private Text mHorsesSerialized; } then whenever the client receives a Farm instance, it has to take the raw string of horses, and split it in order to reinstantiate the list, something like: // GWT client perhaps Farm farm = rpcCall.getMyFarm(); String horsesSerialized = farm.getHorses(); String[] horseBlocks = horsesSerialized.split(","); for (int i = 0; i < horseBlocks.length; i++) { // .. continue deserializing the individual objects ... } yeah... so hopefully it would be quick to read a Farm instance from the datastore, and the serialization penalty is paid by the client, Thanks

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  • How to know the file type of the file which you are forcing the user to download?

    - by Starx
    I am trying to force the user to download a file. For that my script is: $file = "file\this.zip"; header("Cache-Control: public"); header("Content-Description: File Transfer"); header("Content-Disposition: attachment; filename=$file"); header("Content-Type: application/zip"); //This is what I need header("Content-Transfer-Encoding: binary"); readfile($file); The files I am going to upload my not be .zip all the time so I want to know the content type of the image I am going to receive in $file. How to accomplish this

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  • Ruby xml rpc error handling

    - by stel
    I have a model class Car @@RPCServer = XMLRPC::Client.new("localhost", "/", 8080) def self.count @@RPCServer.call("cars.count") end end If server is not running on localhost:8080 I've got a Errno::ECONNREFUSED error. I want to display an error message to user, how can a handle this error?

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  • Dynamic control click event not firing properly

    - by Wil
    I'm creating a next/previous function for my repeater using pageddatasource. I added the link button control dynamically in my oninit using the following code. LinkButton lnkNext = new LinkButton(); lnkNext.Text = "Next"; lnkNext.Click += new EventHandler(NextPage); if (currentPage != objPagedDataSource.PageCount) { pnlMain.Controls.Add(lnkNext); } So in my initial page_load, the next link comes up fine. There are 5 pages in my objPagedDataSource. currentPage variable is 1. The "NextPage" event handler looks like this public void NextPage(object sender, EventArgs e) { if (HttpContext.Current.Request.Cookies["PageNum"] == null) { HttpCookie cookie = new HttpCookie("PageNum"); cookie.Value = "1"; } else { HttpCookie cookie = HttpContext.Current.Request.Cookies["PageNum"]; cookie.Value = (Convert.ToInt32(cookie.Value) + 1).ToString(); } this.BindRepeater(); } So I am incrementing the cookie I am using to track the page number and then rebinding the repeater. Here is the main issue. The first time I click Next, it works, it goes to Page 2 without any problems. When on Page 2, I click Next, it goes back to Page 1. Seems like the Next event is not wiring up properly. Not sure why, any ideas?

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  • How to handle touch events on UI Controls

    - by Sreelatha
    Hi, I have a query related to Touch events on the UI controls. I have 4 controls on the screen ( UITextField, UISlider, UISwitch, UIButton ). If the user touches any of the control on the screen, I want to fire touchesBegan and touchesEnded events on those controls in which I would implement some code. Please let me know how to fire these events. Thanks in advance, Sreelatha.

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  • Handling large (object) datasets with PHP

    - by Aron Rotteveel
    I am currently working on a project that extensively relies on the EAV model. Both entities as their attributes are individually represented by a model, sometimes extending other models (or at least, base models). This has worked quite well so far since most areas of the application only rely on filtered sets of entities, and not the entire dataset. Now, however, I need to parse the entire dataset (IE: all entities and all their attributes) in order to provide a sorting/filtering algorithm based on the attributes. The application currently consists of aproximately 2200 entities, each with aproximately 100 attributes. Every entity is represented by a single model (for example Client_Model_Entity) and has a protected property called $_attributes, which is an array of Attribute objects. Each entity object is about 500KB, which results in an incredible load on the server. With 2000 entities, this means a single task would take 1GB of RAM (and a lot of CPU time) in order to work, which is unacceptable. Are there any patterns or common approaches to iterating over such large datasets? Paging is not really an option, since everything has to be taken into account in order to provide the sorting algorithm.

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  • Handling a Long Running jsp request on the server using Ajax and threads

    - by John Blue
    I am trying to implement a solution for a long running process on the server where it is taking about 10 min to process a pdf generation request. The browser bored/timesout at the 5 mins. I was thinking to deal with this using a Ajax and threads. I am using regular javascript for ajax. But I am stuck with it. I have reached till the point where it sends the request to the servlet and the servlet starts the thread.Please see the below code public class HelloServlet extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("POST request!!"); LongProcess longProcess = new LongProcess(); longProcess.setDaemon(true); longProcess.start(); request.getSession().setAttribute("longProcess", longProcess); request.getRequestDispatcher("index.jsp").forward(request, response); } } class LongProcess extends Thread { public void run() { System.out.println("Thread Started!!"); while (progress < 10) { try { sleep(2000); } catch (InterruptedException ignore) {} progress++; } } } Here is my AJax call <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html><head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>My Title</title> <script language="JavaScript" > function getXMLObject() //XML OBJECT { var xmlHttp = false; xmlHttp = new XMLHttpRequest(); //For Mozilla, Opera Browsers return xmlHttp; // Mandatory Statement returning the ajax object created } var xmlhttp = new getXMLObject(); //xmlhttp holds the ajax object function ajaxFunction() { xmlhttp.open("GET","HelloServlet" ,true); xmlhttp.onreadystatechange = handleServerResponse; xmlhttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded'); xmlhttp.send(null); } function handleServerResponse() { if (xmlhttp.readyState == 4) { if(xmlhttp.status == 200) { document.forms[0].myDiv.value = xmlhttp.responseText; setTimeout(ajaxFunction(), 2000); } else { alert("Error during AJAX call. Please try again"); } } } function openPDF() { document.forms[0].method = "POST"; document.forms[0].action = "HelloServlet"; document.forms[0].submit(); } function stopAjax(){ clearInterval(intervalID); } </script> </head> <body><form name="myForm"> <table><tr><td> <INPUT TYPE="BUTTON" NAME="Download" VALUE="Download Queue ( PDF )" onclick="openPDF();"> </td></tr> <tr><td> Current status: <div id="myDiv"></div>% </td></tr></table> </form></body></html> But I dont know how to proceed further like how will the thread communicate the browser that the process has complete and how should the ajax call me made and check the status of the request. Please let me know if I am missing some pieces. Any suggestion if helpful.

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  • .net exception pool

    - by javier
    I want to create a mecanism in a large .net application to handle all the exceptions in the application, and to save the error messages (in db or log file) so these errors can be fixed, and so we are aware of the problems in the application. Does anyone know a good way of creating a library to handle and process all the exceptions?. Are there any tools around that can simplify my task. What aproach would you suggest me to take.... If you previously implemented something similar to what I want to do, I do want to heard from you Thanks all

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  • Why does "return ERROR" only work with exceptions?

    - by ThreaT
    In the struts.xml I use: <result name="error">error</result> Then in my action I use: addActionError("ERROR RETURNED"); return ERROR; When I submit the form then it just goes to a blank page and does nothing. However, if I FORCE an exception to be thrown in the action then it goes to the error page and shows the ActionError message. So am I doing this wrong? If so, how should I tell struts to show an error page using "if statements" instead of relying solely on expensive try catches? EDIT 1: I'm using struts 2 version: 2.1.8.1 EDIT 2: For example, here is my action code that I'm using to test: String test = ""; int number = 0; try { if (number == 1) { System.out.println("number 1: " + number); test = SUCCESS; } else if (number == 2) { System.out.println("number 2: " + number); addActionError("ERROR RETURNED?"); addActionMessage("TESTTEST"); test = ERROR; } else if (number == 3) { System.out.println("number 3: " + number); addActionError("ERROR RETURNED?"); addActionMessage("TESTTEST"); test = INPUT; } else { System.out.println("number 4: " + number); test = LOGIN; } } catch (Exception e) { addActionError("ERROR RETURNED? " + e); } return test; And here is my JSP code: <s:form action="number_save" method="post"> <s:textfield name="number" label="Enter number" /> </s:form> <s:actionerror /> <s:fielderror /> <s:actionmessage /> EDIT 3: Here is a longer version of my struts.xml: <action name="number" method="numberCreate" class="NumberActionBean"> <result>number.jsp</result> </action> <action name="error"> <result>error.jsp</result> </action> <action name="number_save" method="numberSave" class="NumberActionBean"> <interceptor-ref name="defaultStack"></interceptor-ref> <result name="success" type="redirect">index</result> <result name="input" type="redirect">number</result> <result name="error">error</result> <result name="login" type="redirect">login</result> <result name="none">number</result> </action> EDIT 4: My error.jsp is simply a <s:actionerror /> tag with the general taglibs and html tags...

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  • Excel VBA: Error Handling with Case Statement

    - by AME
    I am trying to validate a file that is uploaded by the user using the code below. The error handler checks the top row of the uploaded file for three specific column names. If one or more of the column names is not present, the program should return a prompt to the user notifying them which column(s) are missing from the file that they uploaded and then close the file. There are a couple issues with my current VBA code that I am seeking help with: The prompt doesn't specify which column(s) are missing to the user. The error handler is triggered even when all required columns are present in the uploaded file. Code: Sub getworkbook() ' Get workbook... Dim ws As Worksheet Dim filter As String Dim targetWorkbook As Workbook, wb As Workbook Dim Ret As Variant Set targetWorkbook = Application.ActiveWorkbook ' get the customer workbook filter = ".xlsx,.xls" caption = "Please select an input file " Ret = Application.GetOpenFilename(filter, , caption) If Ret = False Then Exit Sub Set wb = Workbooks.Open(Ret) On Error GoTo ErrorLine: 'Check for columns var1 = ActiveSheet.Range("1:1").Find("variable1", LookIn:=xlValues, LookAt:=xlWhole, MatchCase:=True).Column var2 = ActiveSheet.Range("1:1").Find("variable2", LookIn:=xlValues, LookAt:=xlWhole, MatchCase:=True).Column var3 = ActiveSheet.Range("1:1").Find("variable3", LookIn:=xlValues, LookAt:=xlWhole, MatchCase:=True).Column ErrorLine: MsgBox ("The selected file is missing a key data column, please upload a correctly formated file.") If Error = True Then ActiveWorkSheet.Close wb.Sheets(1).Move Before:=targetWorkbook.Sheets("Worksheet2") ActiveSheet.Name = "DATA" End Sub

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  • Handling large datasets with PHP/Drupal

    - by jo
    Hi all, I have a report page that deals with ~700k records from a database table. I can display this on a webpage using paging to break up the results. However, my export to PDF/CSV functions rely on processing the entire data set at once and I'm hitting my 256MB memory limit at around 250k rows. I don't feel comfortable increasing the memory limit and I haven't got the ability to use MySQL's save into outfile to just serve a pre-generated CSV. However, I can't really see a way of serving up large data sets with Drupal using something like: $form = array(); $table_headers = array(); $table_rows = array(); $data = db_query("a query to get the whole dataset"); while ($row = db_fetch_object($data)) { $table_rows[] = $row->some attribute; } $form['report'] = array('#value' => theme('table', $table_headers, $table_rows); return $form; Is there a way of getting around what is essentially appending to a giant array of arrays? At the moment I don't see how I can offer any meaningful report pages with Drupal due to this. Thanks

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  • Java - Handling Non-Blocking Calls

    - by sarav
    In my application I am using a third-party API. It is a non-blocking method which returns immediately. I have a collection of elements over which I have to invoke this method. Now, my problem is that I have to find a way till all the method execution gets completed and do my next operation. How can I handle this? I cannot modify the third-party API. In short it looks like this for(Object object: objects){ methodA(object); //this is a non-blocking call and returns immediately } // here I want to do my next task only after all the methodA calls completed execution

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  • Flexible string handling in Visual Studio 2008 C++

    - by David
    I'm slowly starting to get the hang of the _T stuff in Visual Studio 2008 c++, but a few things still elude me. I can see the benefit of the flexibility, but if I can't get the basics soon, I think I'll go back to the standard way of doing this - much less confusing. The idea with the code below is that it scans the parameters for -d and then stores the text that follows that in the string variable fileDir. It also ignores any other parameters. Any help is appreciated. //Console application Parameters::Parameters(int argc, _TCHAR* argv[]) { _Tstring fileDir; // Is there some kind of _t variable to use here for a string? for (int i = 0; i < argc; i = i + 1) { if (_tccmp(argv[i], _T("-d")) == 0) // this appeared to accept anything starting with - { i = i + 1; fileDir = argv[i] } } _tprintf("Parameter value found: %s\n", fileDir); }

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  • Ruby Methods: return an usage string when insufficient arguments are given

    - by Shyam
    Hi, After creating a serious bunch of classes, with initialize methods, loading them in IRb requires to look back at the code. However, I think it should be easy enough to return a usage message, instead of: ArgumentError: wrong number of arguments (0 for 9) So I prefer to return a string with the human readable arguments, by example using "puts" or just a return of a string. Now I have seen the rescue keyword inside begin-end code, but I wonder how I could catch the ArgumentError when the initialize method is called. Thank you for your answers, feedback and comments!

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  • How can a client gracefully detect when a server disconnects?

    - by Ummar
    I am working on a client-server application. The client continuously reads data from server, so when a server is closed or disconnects then the client crashes. I tried a try/catch block, but it didn't work. My client application is written in C++. I want the client to display some proper message like "Server disconnected," then exit.

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  • Swing and handling threads

    - by James P.
    There's a couple questions here on StackOverflow on the subject of threading with the Swing api but things still aren't clear. What is the issue with the EDT, what is the proper way to initiate a Thread with Swing and in what cases should it be used? P.S: Any sources in terms of good practises would be appreciated.

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