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• Static linking in Qt --> link errors in VS 2008

  - by ChruS

  Today I dediced to make static linking in Qt. I used Qt4 with Visual Studio and static C runtime article. The 3rd step took quite a long time. When it was finished I opened my project in VS 2008, made Build->Clean Solution and try to Release. Unfortunately I got link errors: warning LNK4098: defaultlib 'libcmt.lib' conflicts with use of other libs; use /NODEFAULTLIB:library error LNK2019: unresolved external symbol "private: static struct QString::Data QString::shared_null" (?shared_null@QString@@0UData@1@A) referenced in function "public: __thiscall QString::QString(void)" (??0QString@@QAE@XZ) error LNK2019: unresolved external symbol "private: static struct QByteArray::Data QByteArray::shared_null" (?shared_null@QByteArray@@0UData@1@A) referenced in function "public: __thiscall QByteArray::QByteArray(void)" (??0QByteArray@@QAE@XZ) error LNK2001: unresolved external symbol "private: static struct QByteArray::Data QByteArray::shared_null" (?shared_null@QByteArray@@0UData@1@A) error LNK2001: unresolved external symbol "public: static struct QMetaObject const QDialog::staticMetaObject" (?staticMetaObject@QDialog@@2UQMetaObject@@B) error LNK2001: unresolved external symbol "public: static struct QMetaObject const QDialog::staticMetaObject" (?staticMetaObject@QDialog@@2UQMetaObject@@B) error LNK2001: unresolved external symbol "public: static struct QMetaObject const QDialog::staticMetaObject" (?staticMetaObject@QDialog@@2UQMetaObject@@B) error LNK2019: unresolved external symbol "public: static enum QSysInfo::WinVersion const QSysInfo::WindowsVersion" (?WindowsVersion@QSysInfo@@2W4WinVersion@1@B) referenced in function _WinMain@16 What i did wrong? Help to fix this pls.

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• Serial Communication between Java RXTX and Arduino

  - by SharpBarb

  I'm trying to communicate between my PC (Windows 7 using Netbeans and RXTX) with an Arduino Pro, using the serial port. The Arduino is actually connected to the PC using an FTDI cable. The code is based on the Java SimpleRead.Java found here. Currently the Arduino simply prints out a string when it starts up. My Java program should print the number of bytes that have been read and then print out the contents. The Java program works, sort of... If the string is long (10 bytes or so) the output will get broken up. So if on the Arduino I print Serial.println("123456789123456789"); //20 bytes including '\r' and '\n' The output of my Java program may look something like: Number of Bytes: 15 1234567891234 Number of Bytes: 5 56789 or Number of Bytes: 12 1234567891 Number of Bytes: 8 23456789 I'm thinking it's a timing problem, because when I manually go through the code using the debugger, the result string is always what it should be: one 20 byte string. I've been messing with various things but I haven't been able to fix the problem. Here is the part of the code that is giving me problems: static int baudrate = 9600, dataBits = SerialPort.DATABITS_8, stopBits = SerialPort.STOPBITS_1, parity = SerialPort.PARITY_NONE; byte[] readBuffer = new byte[128]; ... ... public void serialEvent(SerialPortEvent event) { if (event.getEventType() == SerialPortEvent.DATA_AVAILABLE) { try { if (input.available() > 0) { //Read the InputStream and return the number of bytes read numBytes = input.read(readBuffer); String result = new String(readBuffer,0,numBytes); System.out.println("Number of Bytes: " + numBytes); System.out.println(result); } } catch (IOException e) { System.out.println("Data Available Exception"); } }

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• WPF Storyboard delay in playing wma files

  - by Rita

  I'm a complete beginner in WPF and have an app that uses StoryBoard to play a sound. public void PlaySound() { MediaElement m = (MediaElement)audio.FindName("MySound.wma"); m.IsMuted = false; FrameworkElement audioKey = (FrameworkElement)keys.FindName("MySound"); Storyboard s = (Storyboard)audioKey.FindResource("MySound.wma"); s.Begin(audioKey); } <Storyboard x:Key="MySound.wma"> <MediaTimeline d:DesignTimeNaturalDuration="1.615" BeginTime="00:00:00" Storyboard.TargetName="MySound.wma" Source="Audio\MySound.wma"/> </Storyboard> I have a horrible lag and sometimes it takes good 10 seconds for the sound to be played. I suspect this has something to do with the fact that no matter how long I wait - The sound doesn't get played until after I leave the function. I don't understand it. I call Begin, and nothing happens. Is there a way to replace this method, or StoryBoard object with something that plays instantly and without a lag?

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• Problem setText UITextView

  - by Mat

  Hi i have a problem. I have 2 viewcontroller, in the first there is a mapView that implements the function "calloutAccessoryControlTapped" to tap a button on an annotation on the mapView; in the second there is just a UITextView. I want to change the text of the UITextView (and show the SecondViewController) in the second controller once the button on annotation is clicked; here is my code (FirstViewController) Header @interface FirstViewController<MKMapViewDelegate>{ IBOutlet MKMapView *mapView; SecondViewController *secondV;} @end Implementation @implementation FirstViewController - (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view calloutAccessoryControlTapped:(UIControl *)control{ secondV = [[SecondViewController alloc] initWithNibName:@"SecondViewController" bundle:nil]; NSString *myS = @"some text here"; [secondV.myTextView setText:myS]; //Switch from this to the secondview [self presentModalViewController:secondV animated:YES]; @end (SecondViewController) Header @interface SecondViewController{ IBOutlet UITextView *myTextView; } @property(nonatomic, retain)UITextView *postitTextView; - (IBAction)backToMAp; - (void)setText:(NSString *)string; @end Implementation @implementation SecondViewController - (IBAction)backToMAp{ //Back To First View; [self dismissModalViewControllerAnimated:YES];} - (void)setText:(NSString *)string{ myTextView.text = string;} In this code when i tap on the button ([self presentModalViewController:secondV animated:YES];) on annotation the first time the second view show up but the text of UITextView don't change, when i back on the FirstView ([self dismissModalViewControllerAnimated:YES];) and then again tap the button to switch again to secondView the text of UITextView change..... Sorry for long thread and for my bad english!! Thank you stack!

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• Showing/hiding a JPopupMenu from a JButton; FocusListener not working?

  - by M. Joanis

  Hi everyone, I needed a JButton with an attached dropdown style menu. So I took a JPopupMenu and attached it to the JButton in the way you can see in the code below. What it needs to do is this: show the popup when clicked hide it if clicked a second time hide it if an item is selected in the popup hide it if the user clicks somewhere else in the screen These 4 things work, but because of the boolean flag I'm using, if the user clicks somewhere else or selects an item, I have to click twice on the button before it shows up again. That's why I tried to add a FocusListener (which is absolutely not responding) to fix that and set the flag false in these cases. Here are the listeners: (It's in a class extending JButton, so the second listener is on the JButton.) // Show popup on left click. menu.addFocusListener(new FocusListener() { @Override public void focusLost(FocusEvent e) { System.out.println("LOST FOCUS"); isShowingPopup = false; } @Override public void focusGained(FocusEvent e) { System.out.println("GAINED FOCUS"); } }); addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { System.out.println("isShowingPopup: " + isShowingPopup); if (isShowingPopup) { isShowingPopup = false; } else { Component c = (Component) e.getSource(); menu.show(c, -1, c.getHeight()); isShowingPopup = true; } } }); I've been fighting with this for way too long now. If someone can give me a clue about what's wrong with this, it would be great! Thanks!

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• JSF:Resourcebundle Problem with Internationalization

  - by Sven

  I implemented internationalization like in that tutorial! When I change the language in my app. It works. But only until the next request happens. Then language settings are reset to my standard language -.- What am I missing here: LanguageBean.java @ManagedBean(name="language") @SessionScoped public class LanguageBean implements Serializable{ private static final long serialVersionUID = 1L; private String localeCode; private static Map<String,Object> countries; static{ countries = new LinkedHashMap<String,Object>(); countries.put("Deutsch", Locale.GERMAN); //label, value countries.put("English", Locale.ENGLISH); } public Map<String, Object> getCountriesInMap() { return countries; } public String getLocaleCode() { return localeCode; } public void setLocaleCode(String localeCode) { this.localeCode = localeCode; } //value change event listener public void countryLocaleCodeChanged(ValueChangeEvent e){ String newLocaleValue = e.getNewValue().toString(); //loop country map to compare the locale code for (Map.Entry<String, Object> entry : countries.entrySet()) { if(entry.getValue().toString().equals(newLocaleValue)){ FacesContext.getCurrentInstance() .getViewRoot().setLocale((Locale)entry.getValue()); } } } } my facelets template: <h:selectOneMenu value="#{language.localeCode}" onchange="submit()" valueChangeListener="#{language.countryLocaleCodeChanged}"> <f:selectItems value="#{language.countriesInMap}" /> </h:selectOneMenu> faces-config: <application> <locale-config> <default-locale>de</default-locale> </locale-config> <resource-bundle> <base-name>org.dhbw.stg.wwi2008c.mopro.ui.text</base-name> <var>msg</var> </resource-bundle> </application>

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• CS Master's Degree Project vs. Thesis options

  - by Nwosh

  I'm doing a master's degree in computer science, and I'm currently at the point where I have to decide between the thesis and non-thesis options offered by my university. The thesis option was my first choice, it entails taking less courses but tends to take more time doing your thesis. The non-thesis option involves taking more coursework, taking a comprehensive exam, and doing a project in one semester with a faculty member. I'd like to pursue a PhD degree eventually (although not right away, I want to get some years of professional experience first), and I heard that having demonstrated the ability to work on a thesis helps a lot with admission (like: not doing thesis raises questions and suggests not being interested in research) and that the experience itself is very good. At the same time, almost everyone I know who did a thesis at my university took a long time (2-3 years), in theory it could be done in 1.5 years. I'm a part time student and I don't really want to spend so much time just getting a master's degree, I could still publish a few papers while working on the project option and I'd be done in a year or so, additionally, I heard having a master's degree with a project and more coursework is more desirable for the industry. So, when applying for a PhD degree in CS at some of the better universities, would the time spent working on the master's thesis help in getting me accepted? Or should I opt for the non-thesis option and hope that the extra coursework and publishing some papers would make up for not working on a thesis?

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• How do I load an image from sd card into coverview

  - by Jolene

  I am doing an application which consists of a cover flow. Currently I am trying to make the cover flow images be obtained from the sd card. But I am not exactly sure how should I display the image. this is the image adapter: public class ImageAdapter extends BaseAdapter { int mGalleryItemBackground; private Context mContext; private FileInputStream fis; private Integer[] mImageIds = { //Instead of using r.drawable, i need to load the images from my sd card instead R.drawable.futsing, R.drawable.futsing2 }; private ImageView[] mImages; public ImageAdapter(Context c) { mContext = c; mImages = new ImageView[mImageIds.length]; } public int getCount() { return mImageIds.length; } public Object getItem(int position) { return position; } public long getItemId(int position) { return position; } @TargetApi(8) public View getView(int position, View convertView, ViewGroup parent) { int screenSize = getResources().getConfiguration().screenLayout & Configuration.SCREENLAYOUT_SIZE_MASK; ImageView i = new ImageView(mContext); i.setImageResource(mImageIds[position]); switch(screenSize) { case Configuration.SCREENLAYOUT_SIZE_XLARGE: //Toast.makeText(this, "Small screen",Toast.LENGTH_LONG).show(); Display display4 = ((WindowManager) context.getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay(); int rotation4 = display4.getRotation(); Log.d("XLarge:",String.valueOf(rotation4)); /** LANDSCAPE **/ if(rotation4 == 0 || rotation4 == 2) { i.setLayoutParams(new CoverFlow.LayoutParams(300, 300)); i.setScaleType(ImageView.ScaleType.CENTER_INSIDE); BitmapDrawable drawable = (BitmapDrawable) i.getDrawable(); drawable.setAntiAlias(true); return i; } /** PORTRAIT **/ else if (rotation4 == 1 || rotation4 == 3) { i.setLayoutParams(new CoverFlow.LayoutParams(650, 650)); i.setScaleType(ImageView.ScaleType.CENTER_INSIDE); BitmapDrawable drawable = (BitmapDrawable) i.getDrawable(); drawable.setAntiAlias(true); return i; } break; default: } return null; } /** Returns the size (0.0f to 1.0f) of the views * depending on the 'offset' to the center. */ public float getScale(boolean focused, int offset) { /* Formula: 1 / (2 ^ offset) */ return Math.max(0, 1.0f / (float)Math.pow(2, Math.abs(offset))); } } and this is how i download and save the file. I need to use the image saved and upload it into my coverflow // IF METHOD TO DOWNLOAD IMAGE void downloadFile() { new Thread(new Runnable(){ // RUN IN BACKGROUND THREAD TO AVOID FREEZING OF UI public void run(){ Bitmap bmImg; URL myFileUrl = null; try { //for (int i = 0; i < urlList.size(); i ++) //{ //url = urlList.get(i); myFileUrl = new URL("http://static.adzerk.net/Advertisers/d18eea9d28f3490b8dcbfa9e38f8336e.jpg"); // RETRIEVE IMAGE URL //} } catch (MalformedURLException e) { e.printStackTrace(); } try { HttpURLConnection conn = (HttpURLConnection) myFileUrl.openConnection(); conn.setDoInput(true); conn.connect(); InputStream in = conn.getInputStream(); Log.i("im connected", "Download"); bmImg = BitmapFactory.decodeStream(in); saveFile(bmImg); } catch (IOException e) { e.printStackTrace(); }} }).start(); // START THREAD } // SAVE THE IMAGE AS JPG FILE private void saveFile(Bitmap bmImg) { File filename; try { // GET EXTERNAL STORAGE, SAVE FILE THERE File storagePath = new File(Environment.getExternalStorageDirectory(),"Covers"); storagePath.mkdirs(); filename = new File(storagePath + "/image.jpg"); FileOutputStream out = new FileOutputStream(filename); bmImg.compress(Bitmap.CompressFormat.JPEG, 90, out); out.flush(); out.close(); MediaStore.Images.Media.insertImage(getContentResolver(),filename.getAbsolutePath(), filename.getName(), filename.getName()); // ONCE THE DOWNLOAD FINISHES, CLOSE DIALOG Toast.makeText(getApplicationContext(), "Image Saved!", Toast.LENGTH_SHORT).show(); } catch (Exception e) { e.printStackTrace(); } }

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• Two strange efficiency problems in Mathematica

  - by Jess Riedel

  FIRST PROBLEM I have timed how long it takes to compute the following statements (where V[x] is a time-intensive function call): Alice = Table[V[i],{i,1,300},{1000}]; Bob = Table[Table[V[i],{i,1,300}],{1000}]^tr; Chris_pre = Table[V[i],{i,1,300}]; Chris = Table[Chris_pre,{1000}]^tr; Alice, Bob, and Chris are identical matricies computed 3 slightly different ways. I find that Chris is computed 1000 times faster than Alice and Bob. It is not surprising that Alice is computed 1000 times slower because, naively, the function V must be called 1000 more times than when Chris is computed. But it is very surprising that Bob is so slow, since he is computed identically to Chris except that Chris stores the intermediate step Chris_pre. Why does Bob evaluate so slowly? SECOND PROBLEM Suppose I want to compile a function in Mathematica of the form f(x)=x+y where "y" is a constant fixed at compile time (but which I prefer not to directly replace in the code with its numerical because I want to be able to easily change it). If y's actual value is y=7.3, and I define f1=Compile[{x},x+y] f2=Compile[{x},x+7.3] then f1 runs 50% slower than f2. How do I make Mathematica replace "y" with "7.3" when f1 is compiled, so that f1 runs as fast as f2? Many thanks!

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• C file read leaves garbage characters

  - by KJ

  Hi. I'm trying to read the contents of a file into my program but I keep occasionally getting garbage characters at the end of the buffers. I haven't been using C a lot (rather I've been using C++) but I assume it has something to do with streams. I don't really know what to do though. I'm using MinGW. Here is the code (this gives me garbage at the end of the second read): include include char* filetobuf(char *file) { FILE *fptr; long length; char *buf; fptr = fopen(file, "r"); /* Open file for reading */ if (!fptr) /* Return NULL on failure */ return NULL; fseek(fptr, 0, SEEK_END); /* Seek to the end of the file */ length = ftell(fptr); /* Find out how many bytes into the file we are */ buf = (char*)malloc(length+1); /* Allocate a buffer for the entire length of the file and a null terminator */ fseek(fptr, 0, SEEK_SET); /* Go back to the beginning of the file */ fread(buf, length, 1, fptr); /* Read the contents of the file in to the buffer */ fclose(fptr); /* Close the file */ buf[length] = 0; /* Null terminator */ return buf; /* Return the buffer */ } int main() { char* vs; char* fs; vs = filetobuf("testshader.vs"); fs = filetobuf("testshader.fs"); printf("%s\n\n\n%s", vs, fs); free(vs); free(fs); return 0; } The filetobuf function is from this example http://www.opengl.org/wiki/Tutorial2:_VAOs,_VBOs,_Vertex_and_Fragment_Shaders_%28C_/_SDL%29. It seems right to me though. So anyway, what's up with that?

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• accelerating Wheel - psychtoolbox in matlab

  - by ariel

  Hi I am trying to write a code that will show an acceleration wheel. as long as the user press 'a' the wheel should accelerate counterclock wize. the thing is that it turn in the right direction but it doesn't accelerate. This is the code I am using . PTB-3 windows XP. img=imread('c:\images.jpg'); [yimg,ximg,z]=size(img); rot_spd = 1; larrow = KbName('a'); % modify this for Windows rarrow = KbName('b'); [w,rect]=Screen('OpenWindow',0,[0 0 0]); sx = 400; % desired x-size of image (pixels) sy = yimg*sx/ximg; % desired y-size--keep proportional t = Screen('MakeTexture',w,img); bdown=0; th = 0; % initial rotation angle (degrees) HideCursor while(~any(bdown)) % exit loop if mouse button is pressed [x,y,bdown]=GetMouse; [keyisdown,secs,keycode] = KbCheck; if(keycode(larrow)) th = th - rot_spd-1; % accelerate counterclockwise th end if(keycode(rarrow)) th = th + rot_spd+1; % accelerate clockwise th end destrect=[x-sx/2,y-sy/2,x+sx/2,y+sy/2]; Screen('DrawTexture',w,t,[],destrect,th); Screen('Flip',w); end Screen('Close',w) ShowCursor If anyone has an odea why it doesn't accelerate I'd appriciate it very much. Ariel

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• Which CEP product to start with?

  - by Andreas

  Hi, I want to learn more on how to build CEP based applications. So I looked around and found several products (overview found here: http://rulecore.com/CEPblog/?page_id=47). But as there are quite a few at the moment, I don't know which is the best to start with. And overall I just would consider the one available for free. The rest is a bit to expensive for just private use ;) Esper is for free, but without Esper studio it seems quite tedious to develop a cep app. Streambase offers a free trial, but I couldn't find out how long you can use this (if only for a month, no that helpful for longer research). Oracle CEP suite seems quite complete, but in the cep scene - as far as I can see - it is the least recognized compared to Esper or Streambase. So do you have any hints on what is the best way to start with cep development? Is it worth to spent time on working through the oracle documenation or is it better to start with Esper or Streambase? Cheers, Andreas

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• Separation of multipage tiff with compression "CCITT T.6" very slow

  - by Alex

  I need to separate multiframe tiff files, and use the following method: public static Image[] GetFrames(Image sourceImage) { Guid objGuid = sourceImage.FrameDimensionsList[0]; FrameDimension objDimension = new FrameDimension(objGuid); int frameCount = sourceImage.GetFrameCount(objDimension); Image[] images = new Image[frameCount]; for (int i = 0; i < frameCount; i++) { MemoryStream ms = new MemoryStream(); sourceImage.SelectActiveFrame(objDimension, i); sourceImage.Save(ms, ImageFormat.Tiff); images[i] = Image.FromStream(ms); } return images; } It works fine, but if the source image was encoded using the CCITT T.6 compression, separating a 20-frame-file takes up to 15 seconds on my 2,5ghz CPU.(edit: One core is at 100% during the process) When saving the images afterward to a single file using standard compression (LZW), the separation time of the LZW-file is under 1 second. Saving with CCITT compression also takes very long. Is there a way to speed up the process?

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• Workaround for GNU Make 3.80 eval bug

  - by bengineerd

  I'm trying to create a generic build template for my Makefiles, kind of like they discuss in the eval documentation. I've run into a known bug with GNU Make 3.80. When $(eval) evaluates a line that is over 193 characters, Make crashes with a "Virtual Memory Exhausted" error. The code I have that causes the issue looks like this. SRC_DIR = ./src/ PROG_NAME = test define PROGRAM_template $(1)_SRC_DIR = $$(SRC_DIR)$(1)/ $(1)_SRC_FILES = $$(wildcard $$($(1)_SRC_DIR)*.c) $(1)_OBJ_FILES = $$($(1)_SRC_FILES):.c=.o) $$($(1)_OBJ_FILES) : $$($(1)_SRC_FILES) # This is the problem line endef $(eval $(call PROGRAM_template,$(PROG_NAME))) When I run this Makefile, I get gmake: *** virtual memory exhausted. Stop. The expected output is that all .c files in ./src/test/ get compiled into .o files (via an implicit rule). The problem is that $$($(1)_SRC_FILES) and $$($(1)_OBJ_FILES) are together over 193 characters long (if there are enough source files). I have tried running the make file on a directory where there is only 2 .c files, and it works fine. It's only when there are many .c files in the SRC directory that I get the error. I know that GNU Make 3.81 fixes this bug. Unfortunately I do not have the authority or ability to install the newer version on the system I'm working on. I'm stuck with 3.80. So, is there some workaround? Maybe split $$($(1)_SRC_FILES) up and declare each dependency individually within the eval?

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• Source Control Checkin Comments at Top Of Source Files

  - by James Wiseman

  I've noticed a discrepancy with some source files in our system whereby some contain source-control checkin comments, and some do not. These comments are added automatically to the top of the file when it is checked in: * $Log: //vm1/Projects/Morpheus/Sleep.bdy-arc $ -- -- Rev 1.14 Apr 14 2009 15:32:52 John Smith --Fixed bugs 2292 and 2230. This seems to have been quite prevelant in all the compainies with which I have worked, but I must confess that I struggle to see the point. Generally the comments aren't that good, are ofen left by people who have long since departed, and even when they are of a high standard it is difficult to tie them to physical code changes. It also strikes me, that you are physically changing the file that you are checking in. Now, this may not be such a problem with files that will be compiled, but could be a disaster with others, e.g. JavaScript files. So really, my query is what was the motivation in concept behind providing this functionality in the first instance? Does anyone actually find these comments useful? Also, I would be curious to know if this was feature that is commonly supported within Source Control systems. I am aware of it with PVCS, VSS and Subversion (Subversion Keyword Substitution), however I wonder if it is also available in some of the more popular DVCSs. Your help, as always is much appreciated.

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• Servlet/JSP Flow Control: Enums, Exceptions, or Something Else?

  - by Christopher Parker

  I recently inherited an application developed with bare servlets and JSPs (i.e.: no frameworks). I've been tasked with cleaning up the error-handling workflow. Currently, each <form> in the workflow submits to a servlet, and based on the result of the form submission, the servlet does one of two things: If everything is OK, the servlet either forwards or redirects to the next page in the workflow. If there's a problem, such as an invalid username or password, the servlet forwards to a page specific to the problem condition. For example, there are pages such as AccountDisabled.jsp, AccountExpired.jsp, AuthenticationFailed.jsp, SecurityQuestionIncorrect.jsp, etc. I need to redesign this system to centralize how problem conditions are handled. So far, I've considered two possible solutions: Exceptions Create an exception class specific to my needs, such as AuthException. Inherit from this class to be more specific when necessary (e.g.: InvalidUsernameException, InvalidPasswordException, AccountDisabledException, etc.). Whenever there's a problem condition, throw an exception specific to the condition. Catch all exceptions via web.xml and route them to the appropriate page(s) with the <error-page> tag. enums Adopt an error code approach, with an enum keeping track of the error code and description. The descriptions can be read from a resource bundle in the finished product. I'm leaning more toward the enum approach, as an authentication failure isn't really an "exceptional condition" and I don't see any benefit in adding clutter to the server logs. Plus, I'd just be replacing one maintenance headache with another. Instead of separate JSPs to maintain, I'd have separate Exception classes. I'm planning on implementing "error" handling in a servlet that I'm writing specifically for this purpose. I'm also going to eliminate all of the separate error pages, instead setting an error request attribute with the error message to display to the user and forwarding back to the referrer. Each target servlet (Logon, ChangePassword, AnswerProfileQuestions, etc.) would add an error code to the request and redirect to my new servlet in the event of a problem. My new servlet would look something like this: public enum Error { INVALID_PASSWORD(5000, "You have entered an invalid password."), ACCOUNT_DISABLED(5002, "Your account has been disabled."), SESSION_EXPIRED(5003, "Your session has expired. Please log in again."), INVALID_SECURITY_QUESTION(5004, "You have answered a security question incorrectly."); private final int code; private final String description; Error(int code, String description) { this.code = code; this.description = description; } public int getCode() { return code; } public String getDescription() { return description; } }; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String sendTo = "UnknownError.jsp"; String message = "An unknown error has occurred."; int errorCode = Integer.parseInt((String)request.getAttribute("errorCode"), 10); Error errors[] = Error.values(); Error error = null; for (int i = 0; error == null && i < errors.length; i++) { if (errors[i].getCode() == errorCode) { error = errors[i]; } } if (error != null) { sendTo = request.getHeader("referer"); message = error.getDescription(); } request.setAttribute("error", message); request.getRequestDispatcher(sendTo).forward(request, response); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } Being fairly inexperienced with Java EE (this is my first real exposure to JSPs and servlets), I'm sure there's something I'm missing, or my approach is suboptimal. Am I on the right track, or do I need to rethink my strategy?

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• Experience migrating legacy Cobol/PL1 to Java

  - by MadMurf

  ORIGINAL Q: I'm wondering if anyone has had experience of migrating a large Cobol/PL1 codebase to Java? How automated was the process and how maintainable was the output? How did the move from transactional to OO work out? Any lessons learned along the way or resources/white papers that may be of benefit would be appreciated. EDIT 7/7: Certainly the NACA approach is interesting, the ability to continue making your BAU changes to the COBOL code right up to the point of releasing the JAVA version has merit for any organization. The argument for procedural Java in the same layout as the COBOL to give the coders a sense of comfort while familiarizing with the Java language is a valid argument for a large organisation with a large code base. As @Didier points out the $3mil annual saving gives scope for generous padding on any BAU changes going forward to refactor the code on an ongoing basis. As he puts it if you care about your people you find a way to keep them happy while gradually challenging them. The problem as I see it with the suggestion from @duffymo to Best to try and really understand the problem at its roots and re-express it as an object-oriented system is that if you have any BAU changes ongoing then during the LONG project lifetime of coding your new OO system you end up coding & testing changes on the double. That is a major benefit of the NACA approach. I've had some experience of migrating Client-Server applications to a web implementation and this was one of the major issues we encountered, constantly shifting requirements due to BAU changes. It made PM & scheduling a real challenge. Thanks to @hhafez who's experience is nicely put as "similar but slightly different" and has had a reasonably satisfactory experience of an automatic code migration from Ada to Java. Thanks @Didier for contributing, I'm still studying your approach and if I have any Q's I'll drop you a line.

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• OpenNETCF.Stopwatch -> only ticks changing, not Elapsed

  - by pithyless

  I've been trying to track down a bug I thought was thread-related, but I think instead there is an issue with the way I am using OpenNETCF's Stopwatch. I am using OpenNETCF.IoC in my application, but for the sake of simplicity I moved the following code directly into a view: public partial class WorkoutView : SmartPart { ... private Stopwatch stopwatch; public WorkoutView() { ... stopwatch = new Stopwatch(); stopwatch.Reset(); stopwatch.Start(); WorkoutDisplayTimer = new Timer(); WorkoutDisplayTimer.Interval = 500; WorkoutDisplayTimer.Tick += new EventHandler(WorkoutDisplayTimer_Tick); WorkoutDisplayTimer.Enabled = true; } void WorkoutDisplayTimer_Tick(object sender, EventArgs e) { ... stopwatch.Stop(); lbl.Text = stopwatch.ElapsedTicks.ToString() + "NOT WORKING: " + stopwatch.Elapsed.ToString(); stopwatch.Start(); } ... } Long story short, looking at stopwatch in the debugger, the only values that ever get updated are ElapsedTicks, mElapsed, mStartPerfCount. Everything else is always zero. Is this expected behavior? Do I need to call an additional method to have the stopwatch calculate the Elapsed struct? (Note: stopwatch.ElapsedMilliseconds is also zero)

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• SQL Server 2008 Running trigger after Insert, Update locks original table

  - by Polity

  Hi Folks, I have a serious performance problem. I have a database with (related to this problem), 2 tables. 1 Table contains strings with some global information. The second table contains the string stripped down to each individual word. So the string is like indexed in the second table, word by word. The validity of the data in the second table is of less important then the validity of the data in the first table. Since the first table can grow like towards 1*10^6 records and the second table having an average of like 10 words for 1 string can grow like 1*10^7 records, i use a nolock in order to read the second this leaves me free for inserting new records without locking it (Expect many reads on both tables). I have a script which keeps on adding and updating rows to the first table in a MERGE statement. On average, the data beeing merged are like 20 strings a time and the scripts runs like ones every 5 seconds. On the first table, i have a trigger which is beeing invoked on a Insert or Update, which takes the newly inserted or updated data and calls a stored procedure on it which makes sure the data is indexed in the second table. (This takes some significant time). The problem is that when having the trigger disbaled, Reading the first table happens in a few ms. However, when enabling the trigger and your in bad luck of trying to read the first table while this is beeing updated, Our webserver gives you a timeout after 10 seconds (which is way to long anyways). I can quess from this part that when running the trigger, the first table is kept (partially) in a lock untill the trigger is completed. What do you think, if i'm right, is there a easy way around this? Thanks in advance! Cheers, Koen

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• How to avoid an HttpException due to timeout

  - by Dan

  I'm working on a website powered by .NET asp/C# code. The clients require that sessions have a 25 minute timeout. However, sometimes the site is used, and a user stays connected for long periods of time (longer than 25 mins). Session_End is triggered: protected void Session_End(Object sender, EventArgs e) { Hashtable trackingInformaiton = (Hashtable)Application["trackingInformation"]; trackingInformaiton.Remove(Session["trackingID"]); } The user returns some time later, but when they interact with the website, they get an error, and we get this email notification: User: Unauthenticated User Error: System.Web.HttpException Description: Failed to load viewstate. The control tree into which viewstate is being loaded must match the control tree that was used to save viewstate during the previous request... The telling part of the stack trace is System.Web.UI.Control.AddedControl. Apparently, the server has thrown away the session data, and is sending new data, but the client is trying to deal with old data. Hence the error that "the control tree into which viewstate is being loaded [doesn't] match the control tree that was used to save the viewstate during the prevoius request." So here's the question. How can I force instruct the user's browser to redirect to a "you're logged out" screen when the connection times out? (Is it something I should add to the Session_End method?)

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• SmtpClient.SendAsync - How to ensure my application doesn't finish before callback?

  - by James

  Hi, I need to send emails asychronously through a console application. I need to do some DB updates on the callback but my application is exiting before the callback code gets run! How can I stop this from happening in a nice manner rather than simply guessing how long to wait before exiting. I would imagine the Async calls get placed in some form of thread? Is it possible to check if any are waiting to be called? Sample Code private static void SendCompletedCallback(object sender, AsyncCompletedEventArgs e) { // Get the unique identifier for this asynchronous operation. String token = (string) e.UserState; if (e.Cancelled) { Console.WriteLine("[{0}] Send canceled.", token); } if (e.Error != null) { Console.WriteLine("[{0}] {1}", token, e.Error.ToString()); } else { // update DB Console.WriteLine("Message sent."); } } public static void Main(string[] args) { var users = Repository.GetUsers(); SmtpClient client = new SmtpClient("Host"); client.SendCompleted += new SendCompletedEventHandler(SendCompletedCallback); MailAddress from = new MailAddress("[email protected]", "System", Encoding.UTF8); foreach (var user in users) { MailAddress to = new MailAddress(user.Email); MailMessage message = new MailMessage(from, to); message.Body = "This is a test"; message.BodyEncoding = System.Text.Encoding.UTF8; message.Subject = "test message 1" + someArrows; message.SubjectEncoding = System.Text.Encoding.UTF8; string userState = String.Format("Message for user id {0}", user.ID); client.SendAsync(message, userState); message.Dispose(); } // need to wait here until I have received a callback for each message // otherwise the application will exit }

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• Pros and cons of making database IDs consistent and "readable"

  - by gmale

  Question Is it a good rule of thumb for database IDs to be "meaningless?" Conversely, are there significant benefits from having IDs structured in a way where they can be recognized at a glance? What are the pros and cons? Background I just had a debate with my coworkers about the consistency of the IDs in our database. We have a data-driven application that leverages spring so that we rarely ever have to change code. That means, if there's a problem, a data change is usually the solution. My argument was that by making IDs consistent and readable, we save ourselves significant time and headaches, long term. Once the IDs are set, they don't have to change often and if done right, future changes won't be difficult. My coworkers position was that IDs should never matter. Encoding information into the ID violates DB design policies and keeping them orderly requires extra work that, "we don't have time for." I can't find anything online to support either position. So I'm turning to all the gurus here at SA! Example Imagine this simplified list of database records representing food in a grocery store, the first set represents data that has meaning encoded in the IDs, while the second does not: ID's with meaning: Type 1 Fruit 2 Veggie Product 101 Apple 102 Banana 103 Orange 201 Lettuce 202 Onion 203 Carrot Location 41 Aisle four top shelf 42 Aisle four bottom shelf 51 Aisle five top shelf 52 Aisle five bottom shelf ProductLocation 10141 Apple on aisle four top shelf 10241 Banana on aisle four top shelf //just by reading the ids, it's easy to recongnize that these are both Fruit on Aisle 4 ID's without meaning: Type 1 Fruit 2 Veggie Product 1 Apple 2 Banana 3 Orange 4 Lettuce 5 Onion 6 Carrot Location 1 Aisle four top shelf 2 Aisle four bottom shelf 3 Aisle five top shelf 4 Aisle five bottom shelf ProductLocation 1 Apple on aisle four top shelf 2 Banana on aisle four top shelf //given the IDs, it's harder to see that these are both fruit on aisle 4 Summary What are the pros and cons of keeping IDs readable and consistent? Which approach do you generally prefer and why? Is there an accepted industry best-practice?

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• JTable Delete All Rows Exception

  - by Dimitri

  Hi, I'm trying to delete all entrys from my abstractTableModel. As long as I don't delete the last remaining row, everything works fine, but as soon as I delete this one, I get an ArrayOutOfBoundsException. I'm using a DefaultRowSorter and this seems to be the Exception. Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 0 at java.util.Vector.get(Vector.java:694) at graphics.tableModel.MyTableModel.getValueAt(MyTableModel.java:78) at graphics.tableModel.MyTableModel.getColumnClass(MyTableModel.java:90) at javax.swing.table.TableRowSorter.useToString(TableRowSorter.java:224) at javax.swing.DefaultRowSorter.updateUseToString(DefaultRowSorter.java:607) at javax.swing.DefaultRowSorter.sort(DefaultRowSorter.java:556) at javax.swing.DefaultRowSorter.shouldOptimizeChange(DefaultRowSorter.java:1008) at javax.swing.DefaultRowSorter.rowsDeleted(DefaultRowSorter.java:866) at javax.swing.JTable.notifySorter(JTable.java:4262) at javax.swing.JTable.sortedTableChanged(JTable.java:4106) at javax.swing.JTable.tableChanged(JTable.java:4383) at javax.swing.table.AbstractTableModel.fireTableChanged(AbstractTableModel.java:280) my Code to delete all Rows: public void deleteAll() { int size = data.size()-1; data.clear(); this.fireTableRowsDeleted(0, size); } Same thing happens with simply deleting the last existing row. public void deleteRow(int row) { data.remove(row); } the way i'm calling deleteRow: for (int i = rows.length - 1; i >=0; i--) { tm.deleteRow(rows[i]); } tm.fireTableDataChanged(); thanks for your help

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• Java 1.4 singleton containing a mutable field

  - by Philippe

  Hi, I'm working on a legacy Java 1.4 project, and I have a factory that instantiates a csv file parser as a singleton. In my csv file parser, however, I have a HashSet that will store objects created from each line of my CSV file. All that will be used by a web application, and users will be uploading CSV files, possibly concurrently. Now my question is : what is the best way to prevent my list of objects to be modified by 2 users ? So far, I'm doing the following : final class MyParser { private File csvFile = null; private static Set myObjects = Collections.synchronizedSet(new HashSet); public synchronized void setFile(File file) { this.csvFile = file; } public void parse() FileReader fr = null; try { fr = new FileReader(csvFile); synchronized(myObjects) { myObjects.clear(); while(...) { // foreach line of my CSV, create a "MyObject" myObjects.add(new MyObject(...)); } } } catch (Exception e) { //... } } } Should I leave the lock only on the myObjects Set, or should I declare the whole parse() method as synchronized ? Also, how should I synchronize - both - the setting of the csvFile and the parsing ? I feel like my actual design is broken because threads could modify the csv file several times while a possibly long parse process is running. I hope I'm being clear enough, because myself am a bit confused on those multi-synchronization issues. Thanks ;-)

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• javascript class calling XMLHttpRequest internally, then handling onreadystatechange

  - by Radu M

  this thing almost works: function myClass(url) { this.source = url; this.rq = null; this.someOtherProperty = "hello"; // open connection to the ajax server this.start = function() { if (window.XMLHttpRequest) { this.rq = new XMLHttpRequest(); if (this.rq.overrideMimeType) this.rq.overrideMimeType("text/xml"); } else this.rq = new ActiveXObject("Microsoft.XMLHTTP"); try { this.rq.onreadystatechange = connectionEvent; this.rq.open("GET", this.source, true); this.rq.send(null); this.state = 1; } catch (err) { // some error handler here } } function connectionEvent() { alert("i'm here"); alert("this doesnt work: " + this.someOtherProperty); } } // myClass so it's nothing more than having the XMLHttpRequest object as a member of my class, instead of globally defined, and invoking it in the traditional way. however, inside my connectionEvent callback function, the meaning of "this" is lost, even though the function itself is scoped inside myClass. i also made sure that the object that i instantiate from myClass is kept alive long enough (declared global in the script). in all the examples of using javascript classes that i saw, "this" was still available inside the inner functions. for me, it is not, even if i take my function outside and make it a myClass.prototype.connectionEvent. what am i doing wrong? thank you.

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