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• TabHost / TabWidget - Scale Background Image ?

  - by user359519

  I need to scale my TabWidget background images so they maintain aspect ratio. I am using a TabHost with a TabWidget. I am then using setBackgroundDrawable to set the images. I found a close answer here - Background in tab widget ignore scaling. However, I'm not sure just where to add the new Drawable code. (Working with the HelloTabWidget example, none of my modules use RelativeLayout, and I don't see any layout for "tabcontent".) I also found this thread - Android: Scale a Drawable or background image?. According to it, it sounds like I would have to pre-scale my images, which defeats the whole purpose of making them scaleable. I also found another thread where someone subclassed the Drawable class so it would either not scale, or it would scale properly. I can't find it now, but that seems like a LOT to go through when you should just be able to do something simple like mTab.setScaleType(centerInside). Here's my code: main.xml: <?xml version="1.0" encoding="utf-8"?> <TabHost xmlns:android="http://schemas.android.com/apk/res/android" android:id="@android:id/tabhost" android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="@drawable/main_background"> <LinearLayout android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> <FrameLayout android:id="@android:id/tabcontent" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_weight="1"/> <TabWidget android:id="@android:id/tabs" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_weight="0"/> </LinearLayout> </TabHost> main activity: tabHost.setOnTabChangedListener(new OnTabChangeListener() { TabHost changedTabHost = getTabHost(); TabWidget changedTabWidget = getTabWidget(); View changedView = changedTabHost.getTabWidget().getChildAt(0); public void onTabChanged(String tabId) { int selectedTab = changedTabHost.getCurrentTab(); TabWidget tw = getTabWidget(); if(selectedTab == 0) { //setTitle("Missions Timeline"); View tempView = tabHost.getTabWidget().getChildAt(0); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_timeline_on)); tempView = tabHost.getTabWidget().getChildAt(1); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_map_off)); tempView = tabHost.getTabWidget().getChildAt(2); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_search_off)); tempView = tabHost.getTabWidget().getChildAt(3); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_news_off)); tempView = tabHost.getTabWidget().getChildAt(4); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_license_off)); //ImageView iv = (ImageView)tabHost.getTabWidget().getChildAt(0).findViewById(android.R.id.icon); //iv.setImageDrawable(getResources().getDrawable(R.drawable.tab_timeline_on)); //iv = (ImageView)tabHost.getTabWidget().getChildAt(1).findViewById(android.R.id.icon); //iv.setImageDrawable(getResources().getDrawable(R.drawable.tab_map_off)); } else if (selectedTab == 1) { //setTitle("Spinoffs Around You"); View tempView = tabHost.getTabWidget().getChildAt(0); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_timeline_off)); tempView = tabHost.getTabWidget().getChildAt(1); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_map_on)); tempView = tabHost.getTabWidget().getChildAt(2); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_search_off)); tempView = tabHost.getTabWidget().getChildAt(3); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_news_off)); tempView = tabHost.getTabWidget().getChildAt(4); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_license_off)); } I also tried 9patch images, but they wind up being too small. So, what's the best way to go about this?

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• How should I clean up hung grandchild processes when an alarm trips in Perl?

  - by brian d foy

  I have a parallelized automation script which needs to call many other scripts, some of which hang because they (incorrectly) wait for standard input. That's not a big deal because I catch those with alarm. The trick is to shut down those hung grandchild processes when the child shuts down. I thought various incantations of SIGCHLD, waiting, and process groups could do the trick, but they all block and the grandchildren aren't reaped. My solution, which works, just doesn't seem like it is the right solution. I'm not especially interested in the Windows solution just yet, but I'll eventually need that too. Mine only works for Unix, which is fine for now. I wrote a small script that takes the number of simultaneous parallel children to run and the total number of forks: $ fork_bomb <parallel jobs> <number of forks> $ fork_bomb 8 500 This will probably hit the per-user process limit within a couple of minutes. Many solutions I've found just tell you to increase the per-user process limit, but I need this to run about 300,000 times, so that isn't going to work. Similarly, suggestions to re-exec and so on to clear the process table aren't what I need. I'd like to actually fix the problem instead of slapping duct tape over it. I crawl the process table looking for the child processes and shut down the hung processes individually in the SIGALRM handler, which needs to die because the rest of real code has no hope of success after that. The kludgey crawl through the process table doesn't bother me from a performance perspective, but I wouldn't mind not doing it: use Parallel::ForkManager; use Proc::ProcessTable; my $pm = Parallel::ForkManager->new( $ARGV[0] ); my $alarm_sub = sub { kill 9, map { $_->{pid} } grep { $_->{ppid} == $$ } @{ Proc::ProcessTable->new->table }; die "Alarm rang for $$!\n"; }; foreach ( 0 .. $ARGV[1] ) { print "."; print "\n" unless $count++ % 50; my $pid = $pm->start and next; local $SIG{ALRM} = $alarm_sub; eval { alarm( 2 ); system "$^X -le '<STDIN>'"; # this will hang alarm( 0 ); }; $pm->finish; } If you want to run out of processes, take out the kill. I thought that setting a process group would work so I could kill everything together, but that blocks: my $alarm_sub = sub { kill 9, -$$; # blocks here die "Alarm rang for $$!\n"; }; foreach ( 0 .. $ARGV[1] ) { print "."; print "\n" unless $count++ % 50; my $pid = $pm->start and next; setpgrp(0, 0); local $SIG{ALRM} = $alarm_sub; eval { alarm( 2 ); system "$^X -le '<STDIN>'"; # this will hang alarm( 0 ); }; $pm->finish; } The same thing with POSIX's setsid didn't work either, and I think that actually broke things in a different way since I'm not really daemonizing this. Curiously, Parallel::ForkManager's run_on_finish happens too late for the same clean-up code: the grandchildren are apparently already disassociated from the child processes at that point.

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• Does anyone know how to appropriately deal with user timezones in rails 2.3?

  - by Amazing Jay

  We're building a rails app that needs to display dates (and more importantly, calculate them) in multiple timezones. Can anyone point me towards how to work with user timezones in rails 2.3(.5 or .8) The most inclusive article I've seen detailing how user time zones are supposed to work is here: http://wiki.rubyonrails.org/howtos/time-zones... although it is unclear when this was written or for what version of rails. Specifically it states that: "Time.zone - The time zone that is actually used for display purposes. This may be set manually to override config.time_zone on a per-request basis." Keys terms being "display purposes" and "per-request basis". Locally on my machine, this is true. However on production, neither are true. Setting Time.zone persists past the end of the request (to all subsequent requests) and also affects the way AR saves to the DB (basically treating any date as if it were already in UTC even when its not), thus saving completely inappropriate values. We run Ruby Enterprise Edition on production with passenger. If this is my problem, do we need to switch to JRuby or something else? To illustrate the problem I put the following actions in my ApplicationController right now: def test p_time = Time.now.utc s_time = Time.utc(p_time.year, p_time.month, p_time.day, p_time.hour) logger.error "TIME.ZONE" + Time.zone.inspect logger.error ENV['TZ'].inspect logger.error p_time.inspect logger.error s_time.inspect jl = JunkLead.create! jl.date_at = s_time logger.error s_time.inspect logger.error jl.date_at.inspect jl.save! logger.error s_time.inspect logger.error jl.date_at.inspect render :nothing => true, :status => 200 end def test2 Time.zone = 'Mountain Time (US & Canada)' logger.error "TIME.ZONE" + Time.zone.inspect logger.error ENV['TZ'].inspect render :nothing => true, :status => 200 end def test3 Time.zone = 'UTC' logger.error "TIME.ZONE" + Time.zone.inspect logger.error ENV['TZ'].inspect render :nothing => true, :status => 200 end and they yield the following: Processing ApplicationController#test (for 98.202.196.203 at 2010-12-24 22:15:50) [GET] TIME.ZONE#<ActiveSupport::TimeZone:0x2c57a68 @tzinfo=#<TZInfo::DataTimezone: Etc/UTC>, @name="UTC", @utc_offset=0> nil Fri Dec 24 22:15:50 UTC 2010 Fri Dec 24 22:00:00 UTC 2010 Fri Dec 24 22:00:00 UTC 2010 Fri, 24 Dec 2010 22:00:00 UTC +00:00 Fri Dec 24 22:00:00 UTC 2010 Fri, 24 Dec 2010 22:00:00 UTC +00:00 Completed in 21ms (View: 0, DB: 4) | 200 OK [http://www.dealsthatmatter.com/test] Processing ApplicationController#test2 (for 98.202.196.203 at 2010-12-24 22:15:53) [GET] TIME.ZONE#<ActiveSupport::TimeZone:0x2c580a8 @tzinfo=#<TZInfo::DataTimezone: America/Denver>, @name="Mountain Time (US & Canada)", @utc_offset=-25200> nil Completed in 143ms (View: 1, DB: 3) | 200 OK [http://www.dealsthatmatter.com/test2] Processing ApplicationController#test (for 98.202.196.203 at 2010-12-24 22:15:59) [GET] TIME.ZONE#<ActiveSupport::TimeZone:0x2c580a8 @tzinfo=#<TZInfo::DataTimezone: America/Denver>, @name="Mountain Time (US & Canada)", @utc_offset=-25200> nil Fri Dec 24 22:15:59 UTC 2010 Fri Dec 24 22:00:00 UTC 2010 Fri Dec 24 22:00:00 UTC 2010 Fri, 24 Dec 2010 15:00:00 MST -07:00 Fri Dec 24 22:00:00 UTC 2010 Fri, 24 Dec 2010 15:00:00 MST -07:00 Completed in 20ms (View: 0, DB: 4) | 200 OK [http://www.dealsthatmatter.com/test] Processing ApplicationController#test3 (for 98.202.196.203 at 2010-12-24 22:16:03) [GET] TIME.ZONE#<ActiveSupport::TimeZone:0x2c57a68 @tzinfo=#<TZInfo::DataTimezone: Etc/UTC>, @name="UTC", @utc_offset=0> nil Completed in 17ms (View: 0, DB: 2) | 200 OK [http://www.dealsthatmatter.com/test3] Processing ApplicationController#test (for 98.202.196.203 at 2010-12-24 22:16:04) [GET] TIME.ZONE#<ActiveSupport::TimeZone:0x2c57a68 @tzinfo=#<TZInfo::DataTimezone: Etc/UTC>, @name="UTC", @utc_offset=0> nil Fri Dec 24 22:16:05 UTC 2010 Fri Dec 24 22:00:00 UTC 2010 Fri Dec 24 22:00:00 UTC 2010 Fri, 24 Dec 2010 22:00:00 UTC +00:00 Fri Dec 24 22:00:00 UTC 2010 Fri, 24 Dec 2010 22:00:00 UTC +00:00 Completed in 151ms (View: 0, DB: 4) | 200 OK [http://www.dealsthatmatter.com/test] It should be clear above that the 2nd call to /test shows Time.zone set to Mountain, even though it shouldn't. Additionally, checking the database reveals that the test action when run after test2 saved a JunkLead record with a date of 2010-12-22 15:00:00, which is clearly wrong.

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• Find optimal/good-enough strategy and AI for the game 'Proximity'?

  - by smci

  'Proximity' is a strategy game of territorial domination similar to Othello, Go and Risk. Two players, uses a 10x12 hex grid. Game invented by Brian Cable in 2007. Seems to be a worthy game for discussing a) optimal algorithm then b) how to build an AI. Strategies are going to be probabilistic or heuristic-based, due to the randomness factor, and the insane branching factor (20^120). So it will be kind of hard to compare objectively. A compute time limit of 5s per turn seems reasonable. Game: Flash version here and many copies elsewhere on the web Rules: here Object: to have control of the most armies after all tiles have been placed. Each turn you received a randomly numbered tile (value between 1 and 20 armies) to place on any vacant board space. If this tile is adjacent to any ally tiles, it will strengthen each tile's defenses +1 (up to a max value of 20). If it is adjacent to any enemy tiles, it will take control over them if its number is higher than the number on the enemy tile. Thoughts on strategy: Here are some initial thoughts; setting the computer AI to Expert will probably teach a lot: minimizing your perimeter seems to be a good strategy, to prevent flips and minimize worst-case damage like in Go, leaving holes inside your formation is lethal, only more so with the hex grid because you can lose armies on up to 6 squares in one move low-numbered tiles are a liability, so place them away from your main territory, near the board edges and scattered. You can also use low-numbered tiles to plug holes in your formation, or make small gains along the perimeter which the opponent will not tend to bother attacking. a triangle formation of three pieces is strong since they mutually reinforce, and also reduce the perimeter Each tile can be flipped at most 6 times, i.e. when its neighbor tiles are occupied. Control of a formation can flow back and forth. Sometimes you lose part of a formation and plug any holes to render that part of the board 'dead' and lock in your territory/ prevent further losses. Low-numbered tiles are obvious-but-low-valued liabilities, but high-numbered tiles can be bigger liabilities if they get flipped (which is harder). One lucky play with a 20-army tile can cause a swing of 200 (from +100 to -100 armies). So tile placement will have both offensive and defensive considerations. Comment 1,2,4 seem to resemble a minimax strategy where we minimize the maximum expected possible loss (modified by some probabilistic consideration of the value ß the opponent can get from 1..20 i.e. a structure which can only be flipped by a ß=20 tile is 'nearly impregnable'.) I'm not clear what the implications of comments 3,5,6 are for optimal strategy. Interested in comments from Go, Chess or Othello players. (The sequel ProximityHD for XBox Live, allows 4-player -cooperative or -competitive local multiplayer increases the branching factor since you now have 5 tiles in your hand at any given time, of which you can only play one. Reinforcement of ally tiles is increased to +2 per ally.)

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• Win32: IProgressDialog will not disappear until you mouse over it.

  - by Ian Boyd

  i'm using the Win32 progress dialog. The damnest thing is that when i call: progressDialog.StopProgressDialog(); it doesn't disappear. It stays on screen until the user moves her mouse over it - then it suddenly disappers. The call to StopProgressDialog returns right away (i.e. it's not a synchronous call). i can prove this by doing things after the call has returned: private void button1_Click(object sender, EventArgs e) { //Force red background to prove we've started this.BackColor = Color.Red; this.Refresh(); //Start a progress dialog IProgressDialog pd = (IProgressDialog)new ProgressDialog(); pd.StartProgressDialog(this.Handle, null, PROGDLG.Normal, IntPtr.Zero); //The long running operation System.Threading.Thread.Sleep(10000); //Stop the progress dialog pd.SetLine(1, "Stopping Progress Dialog", false, IntPtr.Zero); pd.StopProgressDialog(); pd = null; //Return form to normal color to prove we've stopped. this.BackColor = SystemColors.Control; this.Refresh(); } The form: starts gray turns red to show we've stared turns back to gray color to show we've called stop So the call to StopProgressDialog has returned, except the progress dialog is still sitting there, mocking me, showing the message: Stopping Progress Dialog Doesn't Appear for 10 seconds Additionally, the progress dialog does not appear on screen until the System.Threading.Thread.Sleep(10000); ten second sleep is over. Not limited to .NET WinForms The same code also fails in Delphi, which is also an object wrapper around Window's windows: procedure TForm1.Button1Click(Sender: TObject); var pd: IProgressDialog; begin Self.Color := clRed; Self.Repaint; pd := CoProgressDialog.Create; pd.StartProgressDialog(Self.Handle, nil, PROGDLG_NORMAL, nil); Sleep(10000); pd.SetLine(1, StringToOleStr('Stopping Progress Dialog'), False, nil); pd.StopProgressDialog; pd := nil; Self.Color := clBtnFace; Self.Repaint; end; PreserveSig An exception would be thrown if StopProgressDialog was failing. Most of the methods in IProgressDialog, when translated into C# (or into Delphi), use the compiler's automatic mechanism of converting failed COM HRESULTS into a native language exception. In other words the following two signatures will throw an exception if the COM call returned an error HRESULT (i.e. a value less than zero): //C# void StopProgressDialog(); //Delphi procedure StopProgressDialog; safecall; Whereas the following lets you see the HRESULT's and react yourself: //C# [PreserveSig] int StopProgressDialog(); //Delphi function StopProgressDialog: HRESULT; stdcall; HRESULT is a 32-bit value. If the high-bit is set (or the value is negative) it is an error. i am using the former syntax. So if StopProgressDialog is returning an error it will be automatically converted to a language exception. Note: Just for SaG i used the [PreserveSig] syntax, the returned HRESULT is zero; MsgWait? The symptom is similar to what Raymond Chen described once, which has to do with the incorrect use of PeekMessage followed by MsgWaitForMultipleObjects: "Sometimes my program gets stuck and reports one fewer record than it should. I have to jiggle the mouse to get the value to update. After a while longer, it falls two behind, then three..." But that would mean that the failure is in IProgressDialog, since it fails equally well on CLR .NET WinForms and native Win32 code.

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• Incremental PCA

  - by smichak

  Hi, Lately, I've been looking into an implementation of an incremental PCA algorithm in python - I couldn't find something that would meet my needs so I did some reading and implemented an algorithm I found in some paper. Here is the module's code - the relevant paper on which it is based is mentioned in the module's documentation. I would appreciate any feedback from people who are interested in this. Micha #!/usr/bin/env python """ Incremental PCA calculation module. Based on P.Hall, D. Marshall and R. Martin "Incremental Eigenalysis for Classification" which appeared in British Machine Vision Conference, volume 1, pages 286-295, September 1998. Principal components are updated sequentially as new observations are introduced. Each new observation (x) is projected on the eigenspace spanned by the current principal components (U) and the residual vector (r = x - U(U.T*x)) is used as a new principal component (U' = [U r]). The new principal components are then rotated by a rotation matrix (R) whose columns are the eigenvectors of the transformed covariance matrix (D=U'.T*C*U) to yield p + 1 principal components. From those, only the first p are selected. """ __author__ = "Micha Kalfon" import numpy as np _ZERO_THRESHOLD = 1e-9 # Everything below this is zero class IPCA(object): """Incremental PCA calculation object. General Parameters: m - Number of variables per observation n - Number of observations p - Dimension to which the data should be reduced """ def __init__(self, m, p): """Creates an incremental PCA object for m-dimensional observations in order to reduce them to a p-dimensional subspace. @param m: Number of variables per observation. @param p: Number of principle components. @return: An IPCA object. """ self._m = float(m) self._n = 0.0 self._p = float(p) self._mean = np.matrix(np.zeros((m , 1), dtype=np.float64)) self._covariance = np.matrix(np.zeros((m, m), dtype=np.float64)) self._eigenvectors = np.matrix(np.zeros((m, p), dtype=np.float64)) self._eigenvalues = np.matrix(np.zeros((1, p), dtype=np.float64)) def update(self, x): """Updates with a new observation vector x. @param x: Next observation as a column vector (m x 1). """ m = self._m n = self._n p = self._p mean = self._mean C = self._covariance U = self._eigenvectors E = self._eigenvalues if type(x) is not np.matrix or x.shape != (m, 1): raise TypeError('Input is not a matrix (%d, 1)' % int(m)) # Update covariance matrix and mean vector and centralize input around # new mean oldmean = mean mean = (n*mean + x) / (n + 1.0) C = (n*C + x*x.T + n*oldmean*oldmean.T - (n+1)*mean*mean.T) / (n + 1.0) x -= mean # Project new input on current p-dimensional subspace and calculate # the normalized residual vector g = U.T*x r = x - (U*g) r = (r / np.linalg.norm(r)) if not _is_zero(r) else np.zeros_like(r) # Extend the transformation matrix with the residual vector and find # the rotation matrix by solving the eigenproblem DR=RE U = np.concatenate((U, r), 1) D = U.T*C*U (E, R) = np.linalg.eigh(D) # Sort eigenvalues and eigenvectors from largest to smallest to get the # rotation matrix R sorter = list(reversed(E.argsort(0))) E = E[sorter] R = R[:,sorter] # Apply the rotation matrix U = U*R # Select only p largest eigenvectors and values and update state self._n += 1.0 self._mean = mean self._covariance = C self._eigenvectors = U[:, 0:p] self._eigenvalues = E[0:p] @property def components(self): """Returns a matrix with the current principal components as columns. """ return self._eigenvectors @property def variances(self): """Returns a list with the appropriate variance along each principal component. """ return self._eigenvalues def _is_zero(x): """Return a boolean indicating whether the given vector is a zero vector up to a threshold. """ return np.fabs(x).min() < _ZERO_THRESHOLD if __name__ == '__main__': import sys def pca_svd(X): X = X - X.mean(0).repeat(X.shape[0], 0) [_, _, V] = np.linalg.svd(X) return V N = 1000 obs = np.matrix([np.random.normal(size=10) for _ in xrange(N)]) V = pca_svd(obs) print V[0:2] pca = IPCA(obs.shape[1], 2) for i in xrange(obs.shape[0]): x = obs[i,:].transpose() pca.update(x) U = pca.components print U

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• How to directly rotate CVImageBuffer image in IOS 4 without converting to UIImage?

  - by Ian Charnas

  I am using OpenCV 2.2 on the iPhone to detect faces. I'm using the IOS 4's AVCaptureSession to get access to the camera stream, as seen in the code that follows. My challenge is that the video frames come in as CVBufferRef (pointers to CVImageBuffer) objects, and they come in oriented as a landscape, 480px wide by 300px high. This is fine if you are holding the phone sideways, but when the phone is held in the upright position I want to rotate these frames 90 degrees clockwise so that OpenCV can find the faces correctly. I could convert the CVBufferRef to a CGImage, then to a UIImage, and then rotate, as this person is doing: Rotate CGImage taken from video frame However that wastes a lot of CPU. I'm looking for a faster way to rotate the images coming in, ideally using the GPU to do this processing if possible. Any ideas? Ian Code Sample: -(void) startCameraCapture { // Start up the face detector faceDetector = [[FaceDetector alloc] initWithCascade:@"haarcascade_frontalface_alt2" withFileExtension:@"xml"]; // Create the AVCapture Session session = [[AVCaptureSession alloc] init]; // create a preview layer to show the output from the camera AVCaptureVideoPreviewLayer *previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:session]; previewLayer.frame = previewView.frame; previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill; [previewView.layer addSublayer:previewLayer]; // Get the default camera device AVCaptureDevice* camera = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo]; // Create a AVCaptureInput with the camera device NSError *error=nil; AVCaptureInput* cameraInput = [[AVCaptureDeviceInput alloc] initWithDevice:camera error:&error]; if (cameraInput == nil) { NSLog(@"Error to create camera capture:%@",error); } // Set the output AVCaptureVideoDataOutput* videoOutput = [[AVCaptureVideoDataOutput alloc] init]; videoOutput.alwaysDiscardsLateVideoFrames = YES; // create a queue besides the main thread queue to run the capture on dispatch_queue_t captureQueue = dispatch_queue_create("catpureQueue", NULL); // setup our delegate [videoOutput setSampleBufferDelegate:self queue:captureQueue]; // release the queue. I still don't entirely understand why we're releasing it here, // but the code examples I've found indicate this is the right thing. Hmm... dispatch_release(captureQueue); // configure the pixel format videoOutput.videoSettings = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA], (id)kCVPixelBufferPixelFormatTypeKey, nil]; // and the size of the frames we want // try AVCaptureSessionPresetLow if this is too slow... [session setSessionPreset:AVCaptureSessionPresetMedium]; // If you wish to cap the frame rate to a known value, such as 10 fps, set // minFrameDuration. videoOutput.minFrameDuration = CMTimeMake(1, 10); // Add the input and output [session addInput:cameraInput]; [session addOutput:videoOutput]; // Start the session [session startRunning]; } - (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection { // only run if we're not already processing an image if (!faceDetector.imageNeedsProcessing) { // Get CVImage from sample buffer CVImageBufferRef cvImage = CMSampleBufferGetImageBuffer(sampleBuffer); // Send the CVImage to the FaceDetector for later processing [faceDetector setImageFromCVPixelBufferRef:cvImage]; // Trigger the image processing on the main thread [self performSelectorOnMainThread:@selector(processImage) withObject:nil waitUntilDone:NO]; } }

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• Java & Tomcat: SQL JDBC/JNDI Exceptions

  - by user267581

  I am deploying a webapp from eclipse to tomcat. I am having an issue with my application and JNDI lookups. When the app tries to load the JNDI resource I am this stacktrace: javax.naming.ServiceUnavailableException [Root exception is java.rmi.ConnectException: Connection refused to host: localhost; nested exception is: java.net.ConnectException: Connection refused: connect] at com.sun.jndi.rmi.registry.RegistryContext.lookup(RegistryContext.java:101) at javax.naming.InitialContext.lookup(InitialContext.java:396) at org.objectweb.carol.jndi.spi.AbsContext.lookup(AbsContext.java:134) at org.objectweb.carol.jndi.spi.AbsContext.lookup(AbsContext.java:144) at javax.naming.InitialContext.lookup(InitialContext.java:392) at org.objectweb.carol.jndi.spi.MultiContext.lookup(MultiContext.java:118) at javax.naming.InitialContext.lookup(InitialContext.java:392) at com.theriabook.daoflex.JDBCConnection.getDataSource(JDBCConnection.java:61) at com.theriabook.daoflex.JDBCConnection.getConnection(JDBCConnection.java:73) at com.aramark.data.UsersDAO.doLogin(UsersDAO.java:751) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at flex.messaging.services.remoting.adapters.JavaAdapter.invoke(JavaAdapter.java:406) at flex.messaging.services.RemotingService.serviceMessage(RemotingService.java:183) at flex.messaging.MessageBroker.routeMessageToService(MessageBroker.java:1417) at flex.messaging.endpoints.AbstractEndpoint.serviceMessage(AbstractEndpoint.java:878) at com.farata.remoting.CustomAMFEndpoint.serviceMessage(CustomAMFEndpoint.java:23) at flex.messaging.endpoints.amf.MessageBrokerFilter.invoke(MessageBrokerFilter.java:121) at flex.messaging.endpoints.amf.LegacyFilter.invoke(LegacyFilter.java:158) at flex.messaging.endpoints.amf.SessionFilter.invoke(SessionFilter.java:49) at flex.messaging.endpoints.amf.BatchProcessFilter.invoke(BatchProcessFilter.java:67) at flex.messaging.endpoints.amf.SerializationFilter.invoke(SerializationFilter.java:146) at flex.messaging.endpoints.BaseHTTPEndpoint.service(BaseHTTPEndpoint.java:274) at flex.messaging.MessageBrokerServlet.service(MessageBrokerServlet.java:377) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at com.cti.compiler.env.web.CompilerInvocationInterceptor.doFilter(CompilerInvocationInterceptor.java:25) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447) at java.lang.Thread.run(Thread.java:619) Caused by: java.rmi.ConnectException: Connection refused to host: localhost; nested exception is: java.net.ConnectException: Connection refused: connect at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:601) at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:198) at sun.rmi.transport.tcp.TCPChannel.newConnection(TCPChannel.java:184) at sun.rmi.server.UnicastRef.newCall(UnicastRef.java:322) at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source) at com.sun.jndi.rmi.registry.RegistryContext.lookup(RegistryContext.java:97) ... 41 more Caused by: java.net.ConnectException: Connection refused: connect at java.net.PlainSocketImpl.socketConnect(Native Method) at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333) at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195) at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366) at java.net.Socket.connect(Socket.java:525) at java.net.Socket.connect(Socket.java:475) at java.net.Socket.<init>(Socket.java:372) at java.net.Socket.<init>(Socket.java:186) at sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(RMIDirectSocketFactory.java:22) at sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(RMIMasterSocketFactory.java:128) at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:595) I am really stumped at this error. I am using a WinXP running on a Virtual Machine (VMWare) from a MAC. Any ideas? I have uninstalled/reinstalled tomcat multiple times.

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• DoubleBuffering in Java

  - by DDP

  Hello there, I'm having some trouble implementing DoubleBuffer into my program. Before you faint from the wall of text, you should know that a lot of it is there just in case you need to know. The actual place where I think I'm having problems is in one method. I've recently looked up a tutorial on the gpwiki about double buffering, and decided to try and implement the code they had into the code I have that I'm trying to implement doublebuffer in. I get the following error: "java.lang.IllegalStateException: Component must have a valid peer". I don't know if it makes any difference if you know it or not, but the following is the code with the main method. This is just a Frame that displays the ChronosDisplay class inside it. I omitted irrelevant code with "..." public class CDM extends JFrame { public CDM(String str) { super("CD:M - "+str); try { ... ChronosDisplay theGame = new ChronosDisplay(str); ((Component)theGame).setFocusable(true); add(theGame); } catch(Exception e) { System.out.println("CDM ERROR: " +e); } } public static void main( String args[] ) { CDM run = new CDM("DP_Mini"); } } Here is the code where I think the problem resides (I think the problem is in the paint() method). This class is displayed in the CDM class public class ChronosDisplay extends Canvas implements Runnable { String mapName; public ChronosDisplay (String str) { mapName = str; new Thread(this).start(); setVisible(true); createBufferStrategy(2); } public void paint( Graphics window ) { BufferStrategy b = getBufferStrategy(); Graphics g = null; window.setColor(Color.white); try { g = b.getDrawGraphics(); paintMap(g); paintUnits(g); paintBullets(g); } finally { g.dispose(); } b.show(); Toolkit.getDefaultToolkit().sync(); } public void paintMap( Graphics window ) { TowerMap m = new TowerMap(); try { m = new TowerMap(mapName); for(int x=0; x<m.getRows()*50; x+=50) { for(int y = 0; y<m.getCols()*50; y+=50) { int tileType = m.getLocation(x/50,y/50); Image img; if(tileType == 0) { Tile0 t = new Tile0(x,y); t.draw(window); } ...// More similar if statements for other integers } catch(Exception e) ... } ...// Additional methods not shown here public void run() { try { while(true) { Thread.currentThread().sleep(20); repaint(); } } catch(Exception e) ... } } If you're curious (I doubt it matters), the draw() method in the Tile0 class is: public void draw( Graphics window ) { window.drawImage(img,getX(),getY(),50,50,null); } Any pointers, tips, or solutions are greatly appreciated. Thanks for your time! :D

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• Grails validation problems with sets of data: only getting one error message for all errors in a set

  - by Matt

  Hi, I'm trying to validate a domain class that has a number of subsets. class IebeUser { ... static hasMany = [openUserAnswers:OpenUserAnswer, closedUserAnswers:ClosedUserAnswer] } class OpenUserAnswer { OpenQuestion openQuestion String text static belongsTo = [user:IebeUser] static constraints = { openQuestion(nullable:false) text(blank:false) } } class ClosedUserAnswer { ClosedQuestion closedQuestion ClosedAnswer answer static belongsTo = [user:IebeUser] static constraints = { closedQuestion(nullable:false) answer(nullable:false) } } A closed question has a set of predefined answers and an open question lets the user enter a freeform answer. All is well until I come to validate the object after entry in a form: params: [closedUserAnswers[0].answer.id:, closedUserAnswers[0]:[answer:[id:], answer.id:], password:dfgdfgdf, openUserAnswers[0].text:gdfgdfgdfg, openUserAnswers[0]:[text:gdfgdfgdfg], _isOptedOut:, create:Continue, username:gdfgdfggdf, email:[email protected], closedUserAnswers[1].answer.id:, closedUserAnswers[1]:[answer:[id:], answer.id:], openUserAnswers[1].text:, openUserAnswers[1]:[text:], firstName:dfgdf, lastName:gdfgdfgd, action:save, controller:main] The key bits being: closedUserAnswers[0].answer.id:, closedUserAnswers[0]:[answer:[id:] closedUserAnswers[1].answer.id:, closedUserAnswers[1]:[answer:[id:] openUserAnswers[1].text:, openUserAnswers[1]:[text:] In my tests I have two objects of type closedUserAnswers and two of openUserAnswers. But when I call validation on IebeUser I only get validation errors for the closedUserAnswers or the openUserAnswers as a whole. I don't get validation errors for each object with a problem which is what I need. I really need an error per instance. Does anyone know what I'm doing wrong? Even when I call the validate method against each closedUserAnswer/openUserAnswer I still only get one per type. Here are my errors. Sorry for all the code, but thought I'd include as much of the code as possible so that it makes sense. Field error in object 'uk.co.cascaid.iebe.IebeUser' on field 'openUserAnswers.text': rejected value []; codes [uk.co.cascaid.iebe.OpenUserAnswer.text.blank.error.uk.co.cascaid.iebe.IebeUser.openUserAnswers.text,uk.co.cascaid.iebe.OpenUserAnswer.text.blank.error.openUserAnswers.text,uk.co.cascaid.iebe.OpenUserAnswer.text.blank.error.text,uk.co.cascaid.iebe.OpenUserAnswer.text.blank.error,openUserAnswer.text.blank.error.uk.co.cascaid.iebe.IebeUser.openUserAnswers.text,openUserAnswer.text.blank.error.openUserAnswers.text,openUserAnswer.text.blank.error.text,openUserAnswer.text.blank.error,uk.co.cascaid.iebe.OpenUserAnswer.text.blank.uk.co.cascaid.iebe.IebeUser.openUserAnswers.text,uk.co.cascaid.iebe.OpenUserAnswer.text.blank.openUserAnswers.text,uk.co.cascaid.iebe.OpenUserAnswer.text.blank.text,uk.co.cascaid.iebe.OpenUserAnswer.text.blank,openUserAnswer.text.blank.uk.co.cascaid.iebe.IebeUser.openUserAnswers.text,openUserAnswer.text.blank.openUserAnswers.text,openUserAnswer.text.blank.text,openUserAnswer.text.blank,blank.uk.co.cascaid.iebe.IebeUser.openUserAnswers.text,blank.openUserAnswers.text,blank.text,blank]; arguments [text,class uk.co.cascaid.iebe.OpenUserAnswer]; default message [Property [{0}] of class [{1}] cannot be blank] Field error in object 'uk.co.cascaid.iebe.IebeUser' on field 'closedUserAnswers.answer': rejected value [null]; codes [uk.co.cascaid.iebe.ClosedUserAnswer.answer.nullable.error.uk.co.cascaid.iebe.IebeUser.closedUserAnswers.answer,uk.co.cascaid.iebe.ClosedUserAnswer.answer.nullable.error.closedUserAnswers.answer,uk.co.cascaid.iebe.ClosedUserAnswer.answer.nullable.error.answer,uk.co.cascaid.iebe.ClosedUserAnswer.answer.nullable.error,closedUserAnswer.answer.nullable.error.uk.co.cascaid.iebe.IebeUser.closedUserAnswers.answer,closedUserAnswer.answer.nullable.error.closedUserAnswers.answer,closedUserAnswer.answer.nullable.error.answer,closedUserAnswer.answer.nullable.error,uk.co.cascaid.iebe.ClosedUserAnswer.answer.nullable.uk.co.cascaid.iebe.IebeUser.closedUserAnswers.answer,uk.co.cascaid.iebe.ClosedUserAnswer.answer.nullable.closedUserAnswers.answer,uk.co.cascaid.iebe.ClosedUserAnswer.answer.nullable.answer,uk.co.cascaid.iebe.ClosedUserAnswer.answer.nullable,closedUserAnswer.answer.nullable.uk.co.cascaid.iebe.IebeUser.closedUserAnswers.answer,closedUserAnswer.answer.nullable.closedUserAnswers.answer,closedUserAnswer.answer.nullable.answer,closedUserAnswer.answer.nullable,nullable.uk.co.cascaid.iebe.IebeUser.closedUserAnswers.answer,nullable.closedUserAnswers.answer,nullable.answer,nullable]; arguments [answer,class uk.co.cascaid.iebe.ClosedUserAnswer]; default message [Property [{0}] of class [{1}] cannot be null]

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• Google Analytics V2 SDK for Android EasyTracker giving errors

  - by Prince

  I have followed the tutorial for the new Google Analytics V2 SDK for Android located here: https://developers.google.com/analytics/devguides/collection/android/v2/ Unfortunately whenever I go to run the application the reporting is not working and this is the messages that logcat gives me: 07-09 09:13:16.978: W/Ads(13933): No Google Analytics: Library Incompatible. 07-09 09:13:16.994: I/Ads(13933): To get test ads on this device, call adRequest.addTestDevice("2BB916E1BD6BE6407582A429D763EC71"); 07-09 09:13:17.018: I/Ads(13933): adRequestUrlHtml: <html><head><script src="http://media.admob.com/sdk-core-v40.js"></script><script>AFMA_getSdkConstants();AFMA_buildAdURL({"kw":[],"preqs":0,"session_id":"7925570029955749351","u_sd":2,"seq_num":"1","slotname":"a14fd91432961bd","u_w":360,"msid":"com.mysampleapp.sampleapp","js":"afma-sdk-a-v6.0.1","mv":"8013013.com.android.vending","isu":"2BB916E1BD6BE6407582A429D763EC71","cipa":1,"format":"320x50_mb","net":"wi","app_name":"1.android.com.mysampleapp.sampleapp","hl":"en","u_h":592,"carrier":"311480","ptime":0,"u_audio":3});</script></head><body></body></html> 07-09 09:13:17.041: W/ActivityManager(220): Unable to start service Intent { act=com.google.android.gms.analytics.service.START (has extras) }: not found 07-09 09:13:17.049: W/GAV2(13933): Thread[main,5,main]: Connection to service failed 1 07-09 09:13:17.057: W/GAV2(13933): Thread[main,5,main]: Need to call initializea() and be in fallback mode to start dispatch. 07-09 09:13:17.088: D/libEGL(13933): loaded /system/lib/egl/libGLES_android.so 07-09 09:13:17.096: D/libEGL(13933): loaded /vendor/lib/egl/libEGL_POWERVR_SGX540_120.so 07-09 09:13:17.096: D/libEGL(13933): loaded /vendor/lib/egl/libGLESv1_CM_POWERVR_SGX540_120.so 07-09 09:13:17.096: D/libEGL(13933): loaded /vendor/lib/egl/libGLESv2_POWERVR_SGX540_120.so Here is my code (I have redacted some of the code that had to do with httppost, etc.): package com.mysampleapp.sampleapp; import java.io.BufferedReader; import java.io.InputStream; import java.io.InputStreamReader; import java.util.ArrayList; import java.util.List; import org.apache.http.HttpEntity; import org.apache.http.HttpResponse; import org.apache.http.NameValuePair; import org.apache.http.client.HttpClient; import org.apache.http.client.entity.UrlEncodedFormEntity; import org.apache.http.client.methods.HttpPost; import org.apache.http.impl.client.DefaultHttpClient; import org.apache.http.message.BasicNameValuePair; import org.json.JSONArray; import org.json.JSONObject; import com.google.analytics.tracking.android.EasyTracker; import android.app.Activity; import android.app.ProgressDialog; import android.content.DialogInterface; import android.content.DialogInterface.OnCancelListener; import android.content.Intent; import android.content.SharedPreferences; import android.os.AsyncTask; import android.os.Bundle; import android.preference.PreferenceManager; import android.util.Log; import android.view.View; import android.view.View.OnClickListener; import android.widget.ImageView; import android.widget.TextView; public class viewRandom extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.viewrandom); uservote.setVisibility(View.GONE); new randomViewClass().execute(); } public void onStart() { super.onStart(); EasyTracker.getInstance().activityStart(this); } public void onStop() { super.onStop(); EasyTracker.getInstance().activityStop(this); } }

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• Java Hibernate/C3P0 error: "Could not obtain connection metadata. An attempt by a client to checkout

  - by Allan

  I'm trying to get some code I was passed up and running. It appears to use the Hibernate framework. I've gotten past most of the errors tweaking the configuration, but this one has me dead stumped. It's trying to connect to two databases: gameapp and gamelog. Both exist. It seems to have issues connecting to gamelog, but none connecting to gameapp (later in the init, it connects to and loads other DBs just fine). Below, I've pasted the error and exception stack dump. I imaging there's something else in the configs, so I've also included the configuration file for that db. I know this is very vague, but I'm hoping some pro can see the stupid mistake I'm missing. <?xml version="1.0" encoding="GBK"?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <property name="dialect">org.hibernate.dialect.MySQLDialect</property> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.url">jdbc:mysql://127.0.0.1:3306/gamelog</property> <property name="connection.username">root</property> <property name="connection.password"></property> <property name="connection.useUnicode">true</property> <property name="connection.characterEncoding">UTF-8</property> <property name="hibernate.jdbc.batch_size">100</property> <property name="jdbc.fetch_size">1</property> <property name="hbm2ddl.auto">none</property><!-- update --> <property name="connection.useUnicode">true</property> <property name="show_sql">true</property> <!-- c3p0-configuration --> <property name="hibernate.connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</property> <property name="hibernate.c3p0.min_size">5</property> <property name="hibernate.c3p0.max_size">10</property> <property name="hibernate.c3p0.timeout">30</property> <property name="hibernate.c3p0.idle_test_period">30</property> <property name="hibernate.c3p0.max_statements">0</property> <property name="hibernate.c3p0.acquire_increment">5</property> </session-factory> </hibernate-configuration> Exception and stack trace: 2010-04-30 17:50:00,411 WARN [org.hibernate.cfg.SettingsFactory] - Could not obtain connection metadata java.sql.SQLException: An attempt by a client to checkout a Connection has timed out. at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:106) at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:65) at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:527) at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128) at org.hibernate.connection.C3P0ConnectionProvider.getConnection(C3P0ConnectionProvider.java:35) at org.hibernate.cfg.SettingsFactory.buildSettings(SettingsFactory.java:76) at org.hibernate.cfg.Configuration.buildSettings(Configuration.java:1933) at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1216) at com.database.hibernate.util.HibernateFactory.<init>(Unknown Source) at com.database.hibernate.util.HibernateUtil.<clinit>(Unknown Source) at com.server.databaseop.goodOp.GoodOpImpl.initBreedGoods(Unknown Source) at com.server.databaseop.goodOp.GoodOpImpl.access$000(Unknown Source) at com.server.databaseop.goodOp.GoodOpImpl$1.run(Unknown Source) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:351) at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:178) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:165) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:267) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:636) Caused by: com.mchange.v2.resourcepool.TimeoutException: A client timed out while waiting to acquire a resource from com.mchange.v2.resourcepool.BasicResourcePool@ca470 -- timeout at awaitAvailable() at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1317) at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:557) at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:477) at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:525) ... 18 more

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• What do I need to write a small game on Linux?

  - by Michas

  I want to make a simple game: 2d, single-player, without tons of animations and special effects. I am not interested in ready to use game engines, I want to learn to write some code in a quite universal language. I am using Linux (AMD64) and looking for something easy with nice library for games. I do not want to mix few languages, most of them are in fact fast enough themselves for my needs. Cross platform would be an advantage, however all I need is a good Linux support. I have been considering few solutions. Ruby + Language looks very nice. + I am going to learn Ruby. - I am afraid I can have problems with additional libraries. - This thread about game libraries for Ruby could be longer. SDL + C + It is used for games. + It is very easy to set up. + There is a lot of additional libraries. + It is cross-platform. - The solution is quite low level. - The language is sometimes quite hard to read. QT + C++ + It is very easy to set up. + The standard QT libraries supports everything I can possibly need. + It is cross-platform. + The documentation is good. - The compilation is slow. - The language looks horrible. - The size of standard QT libraries is too big to comprehend. Environment of web browser + I am going to learn something more about this environment. + It is somewhat used for games. + It is quite cross-platform. - It would be too much experimental. Java + It is used for games. + The standard Java libraries supports everything I can possibly need. + It is cross-platform. - It is quite hard to set up. - The size of standard Java libraries is too big to comprehend. - The source code in Java could look better. - I think I do not want to learn Java. Google Go + I am going to learn Google Go. - There is big problem with libraries. - The solution would be quite low level. Python + It looks some people do games in Python, according to this thread. + It looks there are probably more libraries than for Ruby. - The Ruby language looks better. - I think I do not want to learn Python. C++ + something else + It is used for games. + It would be probably cross-platform. + There is a lot of libraries. - I do not need C++ extensions over C. - Compilation could be slow, there are fast compilers for C, not for C++. Haskell + I am going to learn Haskell. - Many things about programming computer games looks too much imperative. - It looks I can have some problems with libraries. - Compilation (GHC) looks slow. There is probably something more to consider. Does anyone have experience in making small games for Linux in non mainstream solutions? Does anyone have an advice for me?

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• Why did I get this error : java.lang.Exception: XMLEncoder: discarding statement Vector.add() ?

  - by Frank

  My Java program look like this : public class Biz_Manager { static Contact_Info_Setting Customer_Contact_Info_Panel; static XMLEncoder XML_Encoder; ...... void Get_Customer_Agent_Shipping_Company_And_Shipping_Agent_Net_Worth_Info() { try { XML_Encoder=new XMLEncoder(new BufferedOutputStream(new FileOutputStream(Customer_Contact_Info_Panel.Contact_Info_File_Path))); XML_Encoder.writeObject(Customer_Contact_Info_Panel.Contacts_Vector); } catch (Exception e) { e.printStackTrace(); } finally { if (XML_Encoder!=null) { XML_Encoder.close(); // <== Error here , line : 9459 XML_Encoder=null; } } } } // ======================================================================= public class Contact_Info_Setting extends JPanel implements ActionListener,KeyListener,ItemListener { public static final long serialVersionUID=26362862L; ...... Vector<Contact_Info_Entry> Contacts_Vector=new Vector<Contact_Info_Entry>(); ...... } // ======================================================================= package Utility; import java.io.*; import java.util.*; import javax.jdo.annotations.IdGeneratorStrategy; import javax.jdo.annotations.IdentityType; import javax.jdo.annotations.PersistenceCapable; import javax.jdo.annotations.Persistent; import javax.jdo.annotations.PrimaryKey; @PersistenceCapable(identityType=IdentityType.APPLICATION) public class Contact_Info_Entry implements Serializable { @PrimaryKey @Persistent(valueStrategy=IdGeneratorStrategy.IDENTITY) public Long Id; public static final long serialVersionUID=26362862L; public String Contact_Id="",First_Name="",Last_Name="",Company_Name="",Branch_Name="",Address_1="",Address_2="",City="",State="",Zip="",Country=""; ...... public boolean B_1; public Vector<String> A_Vector=new Vector<String>(); public Contact_Info_Entry() { } public Contact_Info_Entry(String Other_Id) { this.Other_Id=Other_Id; } ...... public void setId(Long value) { Id=value; } public Long getId() { return Id; } public void setContact_Id(String value) { Contact_Id=value; } public String getContact_Id() { return Contact_Id; } public void setFirst_Name(String value) { First_Name=value; } public String getFirst_Name() { return First_Name; } public void setLast_Name(String value) { Last_Name=value; } public String getLast_Name() { return Last_Name; } public void setCompany_Name(String value) { Company_Name=value; } public String getCompany_Name() { return Company_Name; } ...... } I got this error message : java.lang.Exception: XMLEncoder: discarding statement Vector.add(Contact_Info_Entry); Continuing ... java.lang.Exception: XMLEncoder: discarding statement Vector.add(Contact_Info_Entry); Continuing ... java.lang.Exception: XMLEncoder: discarding statement Vector.add(Contact_Info_Entry); Continuing ... java.lang.Exception: XMLEncoder: discarding statement Vector.add(Contact_Info_Entry); Continuing ... Exception in thread "Thread-8" java.lang.NullPointerException at java.beans.XMLEncoder.outputStatement(XMLEncoder.java:611) at java.beans.XMLEncoder.outputValue(XMLEncoder.java:552) at java.beans.XMLEncoder.outputStatement(XMLEncoder.java:682) at java.beans.XMLEncoder.outputStatement(XMLEncoder.java:687) at java.beans.XMLEncoder.outputValue(XMLEncoder.java:552) at java.beans.XMLEncoder.flush(XMLEncoder.java:398) at java.beans.XMLEncoder.close(XMLEncoder.java:429) at Biz_Manager.Get_Customer_Agent_Shipping_Company_And_Shipping_Agent_Net_Worth_Info(Biz_Manager.java:9459) Seems it can't deal with vector, why ? Anything wrong ? How to fix it ? Frank

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• When should I use indexed arrays of OpenGL vertices?

  - by Tartley

  I'm trying to get a clear idea of when I should be using indexed arrays of OpenGL vertices, drawn with gl[Multi]DrawElements and the like, versus when I should simply use contiguous arrays of vertices, drawn with gl[Multi]DrawArrays. (Update: The consensus in the replies I got is that one should always be using indexed vertices.) I have gone back and forth on this issue several times, so I'm going to outline my current understanding, in the hopes someone can either tell me I'm now finally more or less correct, or else point out where my remaining misunderstandings are. Specifically, I have three conclusions, in bold. Please correct them if they are wrong. One simple case is if my geometry consists of meshes to form curved surfaces. In this case, the vertices in the middle of the mesh will have identical attributes (position, normal, color, texture coord, etc) for every triangle which uses the vertex. This leads me to conclude that: 1. For geometry with few seams, indexed arrays are a big win. Follow rule 1 always, except: For geometry that is very 'blocky', in which every edge represents a seam, the benefit of indexed arrays is less obvious. To take a simple cube as an example, although each vertex is used in three different faces, we can't share vertices between them, because for a single vertex, the surface normals (and possible other things, like color and texture co-ord) will differ on each face. Hence we need to explicitly introduce redundant vertex positions into our array, so that the same position can be used several times with different normals, etc. This means that indexed arrays are of less use. e.g. When rendering a single face of a cube: 0 1 o---o |\ | | \ | | \| o---o 3 2 (this can be considered in isolation, because the seams between this face and all adjacent faces mean than none of these vertices can be shared between faces) if rendering using GL_TRIANGLE_FAN (or _STRIP), then each face of the cube can be rendered thus: verts = [v0, v1, v2, v3] colors = [c0, c0, c0, c0] normal = [n0, n0, n0, n0] Adding indices does not allow us to simplify this. From this I conclude that: 2. When rendering geometry which is all seams or mostly seams, when using GL_TRIANGLE_STRIP or _FAN, then I should never use indexed arrays, and should instead always use gl[Multi]DrawArrays. (Update: Replies indicate that this conclusion is wrong. Even though indices don't allow us to reduce the size of the arrays here, they should still be used because of other performance benefits, as discussed in the comments) The only exception to rule 2 is: When using GL_TRIANGLES (instead of strips or fans), then half of the vertices can still be re-used twice, with identical normals and colors, etc, because each cube face is rendered as two separate triangles. Again, for the same single cube face: 0 1 o---o |\ | | \ | | \| o---o 3 2 Without indices, using GL_TRIANGLES, the arrays would be something like: verts = [v0, v1, v2, v2, v3, v0] normals = [n0, n0, n0, n0, n0, n0] colors = [c0, c0, c0, c0, c0, c0] Since a vertex and a normal are often 3 floats each, and a color is often 3 bytes, that gives, for each cube face, about: verts = 6 * 3 floats = 18 floats normals = 6 * 3 floats = 18 floats colors = 6 * 3 bytes = 18 bytes = 36 floats and 18 bytes per cube face. (I understand the number of bytes might change if different types are used, the exact figures are just for illustration.) With indices, we can simplify this a little, giving: verts = [v0, v1, v2, v3] (4 * 3 = 12 floats) normals = [n0, n0, n0, n0] (4 * 3 = 12 floats) colors = [c0, c0, c0, c0] (4 * 3 = 12 bytes) indices = [0, 1, 2, 2, 3, 0] (6 shorts) = 24 floats + 12 bytes, and maybe 6 shorts, per cube face. See how in the latter case, vertices 0 and 2 are used twice, but only represented once in each of the verts, normals and colors arrays. This sounds like a small win for using indices, even in the extreme case of every single geometry edge being a seam. This leads me to conclude that: 3. When using GL_TRIANGLES, one should always use indexed arrays, even for geometry which is all seams. Please correct my conclusions in bold if they are wrong.

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• NPE when drawing TabWidget in android (only on HTC Magic?)

  - by David Hedlund

  I've received report from the user of an app I've written that he gets FC whenever starting a certain activity. I have not been able to reproduce the issue on the emulator or on my HTC Hero (running 1.5), but this user running HTC Magic (with 1.6) is facing this error every time. What bothers me is that no single step in the stacktrace actually includes any code in my app (com.filmtipset) 01-07 00:10:26.773 I/ActivityManager( 141): Starting activity: Intent { cmp=com.filmtipset/.ViewMovie (has extras) } 01-07 00:10:27.023 D/AndroidRuntime( 2402): Shutting down VM 01-07 00:10:27.023 W/dalvikvm( 2402): threadid=3: thread exiting with uncaught exception (group=0x4001e170) 01-07 00:10:27.023 E/AndroidRuntime( 2402): Uncaught handler: thread main exiting due to uncaught exception 01-07 00:10:27.083 E/AndroidRuntime( 2402): java.lang.NullPointerException 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.widget.TabWidget.dispatchDraw(TabWidget.java:173) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.drawChild(ViewGroup.java:1529) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.drawChild(ViewGroup.java:1529) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.drawChild(ViewGroup.java:1529) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.View.draw(View.java:6552) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.widget.FrameLayout.draw(FrameLayout.java:352) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.drawChild(ViewGroup.java:1531) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.View.draw(View.java:6552) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.widget.FrameLayout.draw(FrameLayout.java:352) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:1883) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewRoot.draw(ViewRoot.java:1332) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewRoot.performTraversals(ViewRoot.java:1097) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewRoot.handleMessage(ViewRoot.java:1613) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.os.Handler.dispatchMessage(Handler.java:99) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.os.Looper.loop(Looper.java:123) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.app.ActivityThread.main(ActivityThread.java:4320) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at java.lang.reflect.Method.invokeNative(Native Method) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at java.lang.reflect.Method.invoke(Method.java:521) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at dalvik.system.NativeStart.main(Native Method) Full dump here if I've missed anything of interest I'm guessing, then, that there might be something wrong with my layout. It's quite verbose, so I'm posting it here, rather than pasting the whole thing on SO. There is a tabwidget, where one tab is connected to the scrollview, svFilmInfo, and one to the linear layout llComments. The tab host is populated as such: Drawable commentSelector = getResources().getDrawable(R.drawable.tabcomment); Drawable infoSelector = getResources().getDrawable(R.drawable.tabinfo); mTabHost = getTabHost(); mTabHost.getTabWidget().setBackgroundColor(Color.BLACK); mTabHost.addTab(mTabHost.newTabSpec("tabInfo").setIndicator("Filminfo", infoSelector).setContent(R.id.svFilmInfo)); mTabHost.addTab(mTabHost.newTabSpec("tabInfo").setIndicator("Kommentarer", commentSelector).setContent(R.id.llComments)); Since I cannot reproduce the error myself, and since I cannot find any mention in the stack trace of what might be causing the error, I don't quite know where to start troubleshooting this. I'd appreciate any pointers.

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• Is it a missing implementation with JPA implementation of hibernate??

  - by Jegan

  Hi all, On my way in understanding the transaction-type attribute of persistence.xml, i came across an issue / discrepency between hibernate-core and JPA-hibernate which looks weird. I am not pretty sure whether it is a missing implementation with JPA of hibernate. Let me post the comparison between the outcome of JPA implementation and the hibernate implementation of the same concept. Environment Eclipse 3.5.1 JSE v1.6.0_05 Hibernate v3.2.3 [for hibernate core] Hibernate-EntityManger v3.4.0 [for JPA] MySQL DB v5.0 Issue 1.Hibernate core package com.expt.hibernate.core; import java.io.Serializable; public final class Student implements Serializable { private int studId; private String studName; private String studEmailId; public Student(final String studName, final String studEmailId) { this.studName = studName; this.studEmailId = studEmailId; } public int getStudId() { return this.studId; } public String getStudName() { return this.studName; } public String getStudEmailId() { return this.studEmailId; } private void setStudId(int studId) { this.studId = studId; } private void setStudName(String studName) { this.studName = stuName; } private void setStudEmailId(int studEmailId) { this.studEmailId = studEmailId; } } 2. JPA implementaion of Hibernate package com.expt.hibernate.jpa; import java.io.Serializable; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.Table; @Entity @Table(name = "Student_Info") public final class Student implements Serializable { @Id @GeneratedValue @Column(name = "STUD_ID", length = 5) private int studId; @Column(name = "STUD_NAME", nullable = false, length = 25) private String studName; @Column(name = "STUD_EMAIL", nullable = true, length = 30) private String studEmailId; public Student(final String studName, final String studEmailId) { this.studName = studName; this.studEmailId = studEmailId; } public int getStudId() { return this.studId; } public String getStudName() { return this.studName; } public String getStudEmailId() { return this.studEmailId; } } Also, I have provided the DB configuration properties in the associated hibernate-cfg.xml [in case of hibernate core] and persistence.xml [in case of JPA (hibernate entity manager)]. create a driver and perform add a student and query for the list of students and print their details. Then the issue comes when you run the driver program. Hibernate core - output Exception in thread "main" org.hibernate.InstantiationException: No default constructor for entity: com.expt.hibernate.core.Student at org.hibernate.tuple.PojoInstantiator.instantiate(PojoInstantiator.java:84) at org.hibernate.tuple.PojoInstantiator.instantiate(PojoInstantiator.java:100) at org.hibernate.tuple.entity.AbstractEntityTuplizer.instantiate(AbstractEntityTuplizer.java:351) at org.hibernate.persister.entity.AbstractEntityPersister.instantiate(AbstractEntityPersister.java:3604) .... .... This exception is flashed when the driver is executed for the first time itself. JPA Hibernate - output First execution of the driver on a fresh DB provided the following output. DEBUG SQL:111 - insert into student.Student_Info (STUD_EMAIL, STUD_NAME) values (?, ?) 17:38:24,229 DEBUG SQL:111 - select student0_.STUD_ID as STUD1_0_, student0_.STUD_EMAIL as STUD2_0_, student0_.STUD_NAME as STUD3_0_ from student.Student_Info student0_ student list size == 1 1 || Jegan || [email protected] second execution of the driver provided the following output. DEBUG SQL:111 - insert into student.Student_Info (STUD_EMAIL, STUD_NAME) values (?, ?) 17:40:25,254 DEBUG SQL:111 - select student0_.STUD_ID as STUD1_0_, student0_.STUD_EMAIL as STUD2_0_, student0_.STUD_NAME as STUD3_0_ from student.Student_Info student0_ Exception in thread "main" javax.persistence.PersistenceException: org.hibernate.InstantiationException: No default constructor for entity: com.expt.hibernate.jpa.Student at org.hibernate.ejb.AbstractEntityManagerImpl.throwPersistenceException(AbstractEntityManagerImpl.java:614) at org.hibernate.ejb.QueryImpl.getResultList(QueryImpl.java:76) at driver.StudentDriver.main(StudentDriver.java:43) Caused by: org.hibernate.InstantiationException: No default constructor for entity: com.expt.hibernate.jpa.Student .... .... Could anyone please let me know if you have encountered this sort of inconsistency? Also, could anyone please let me know if the issue is a missing implementation with JPA-Hibernate? ~ Jegan

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• Can't seem to redirect from a ViewScoped constructor.

  - by Andrew

  I'm having trouble redirecting from a view scoped bean in the case that we don't have the required info for the page in question. The log entry in the @PostContruct is visible in the log right before a NPE relating to the view trying to render itself instead of following my redirect. Why is it ignoring the redirect? Here's my code: @ManagedBean public class WelcomeView { private String sParam; private String aParam; public WelcomeView() { super(); sParam = getURL_Param("surveyName"); aParam = getURL_Param("accountName"); project = fetchProject(sParam, aParam); } @PostConstruct public void redirectWithoutProject() { if (null == project) { try { logger.warn("NO project [" + sParam + "] for account [" + aParam + "]"); FacesContext fc = FacesContext.getCurrentInstance(); fc.getExternalContext().redirect("/errors/noSurvey.jsf"); return; } catch (Exception e) { e.printStackTrace(); } } } .... public boolean getAuthenticated() { if (project.getPasswordProtected()) { return enteredPassword.equals(project.getLoginPassword()); } else return true; } } Here's the stack trace: SEVERE: Error Rendering View[/participant/welcome.xhtml] javax.el.ELException: /templates/participant/welcome.xhtml @80,70 rendered="#{welcomeView.authenticated}": Error reading 'authenticated' on type com.MYCODE.general.controllers.participant.WelcomeView at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:107) at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:190) at javax.faces.component.UIComponentBase.isRendered(UIComponentBase.java:416) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1607) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1616) at javax.faces.render.Renderer.encodeChildren(Renderer.java:168) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:848) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1613) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1616) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1616) at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:380) at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:126) at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:127) at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139) at javax.faces.webapp.FacesServlet.service(FacesServlet.java:313) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at com.MYCODE.general.filters.StatsFilter.doFilter(StatsFilter.java:28) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:433) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:568) at org.apache.catalina.authenticator.SingleSignOn.invoke(SingleSignOn.java:421) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447) at java.lang.Thread.run(Thread.java:637) Caused by: java.lang.NullPointerException at com.MYCODE.general.controllers.participant.WelcomeView$$M$863c205f.getAuthenticated(WelcomeView.java:127) at com.MYCODE.general.controllers.participant.WelcomeView$$A$863c205f.getAuthenticated(<generated>) at com.MYCODE.general.controllers.participant.WelcomeView.getAuthenticated(WelcomeView.java:125) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at javax.el.BeanELResolver.getValue(BeanELResolver.java:62) at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:53) at com.sun.faces.el.FacesCompositeELResolver.getValue(FacesCompositeELResolver.java:72) at org.apache.el.parser.AstValue.getValue(AstValue.java:118) at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:186) at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:102) ... 33 more

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• Play! Framework 1.2.4 --- C3P0 settings to avoid Communications link failure do to idle time

  - by HelpMeStackOverflowMyOnlyHope

  I'm trying to customize my C3P0 settings to avoid the error shown at the bottom of this post. It was suggested at this url --- http://make-it-open.blogspot.com/2008/12/sql-error-0-sqlstate-08s01.html --- to adjust the settings as follows: In hibernate.cfg.xml, write <property name="c3p0.min_size">5</property> <property name="c3p0.max_size">20</property> <property name="c3p0.timeout">1800</property> <property name="c3p0.max_statements">50</property> Then create "c3p0.properties" in your root classpath folder and write c3p0.testConnectionOnCheckout=true c3p0.acquireRetryDelay=1000 c3p0.acquireRetryAttempts=1 I've tried to make those adjustments following the direction of the Play! Framework documentation, where they say use "db.pool..." as follows: db.pool.timeout=1800 db.pool.maxSize=15 db.pool.minSize=5 db.pool.initialSize=5 db.pool.acquireRetryAttempts=1 db.pool.preferredTestQuery=SELECT 1 db.pool.testConnectionOnCheckout=true db.pool.acquireRetryDelay=1000 db.pool.maxStatements=50 Are those settings not going to work? Should I be trying to set them in a different way? With those settings I still get the error shown below, that is due to to long of a idle time. Complete Stack Trace of Error: 23:00:44,932 WARN ~ SQL Error: 0, SQLState: 08S01 2012-04-13T23:00:44+00:00 app[web.1]: 23:00:44,932 ERROR ~ Communications link failure 2012-04-13T23:00:44+00:00 app[web.1]: 2012-04-13T23:00:44+00:00 app[web.1]: The last packet successfully received from the server was 274,847 milliseconds ago. The last packet sent successfully to the server was 7 milliseconds ago. 2012-04-13T23:00:44+00:00 app[web.1]: 23:00:44,934 ERROR ~ Why the driver complains here? 2012-04-13T23:00:44+00:00 app[web.1]: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after connection closed.Connection was implicitly closed by the driver. 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.Util.handleNewInstance(Util.java:407) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.Util.getInstance(Util.java:382) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1013) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:987) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:982) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:927) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.ConnectionImpl.throwConnectionClosedException(ConnectionImpl.java:1213) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.ConnectionImpl.getMutex(ConnectionImpl.java:3101) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.ConnectionImpl.setAutoCommit(ConnectionImpl.java:4975) 2012-04-13T23:00:44+00:00 app[web.1]: at org.hibernate.jdbc.BorrowedConnectionProxy.invoke(BorrowedConnectionProxy.java:74) 2012-04-13T23:00:44+00:00 app[web.1]: at $Proxy49.setAutoCommit(Unknown Source) 2012-04-13T23:00:44+00:00 app[web.1]: at play.db.jpa.JPAPlugin.closeTx(JPAPlugin.java:368) 2012-04-13T23:00:44+00:00 app[web.1]: at play.db.jpa.JPAPlugin.onInvocationException(JPAPlugin.java:328) 2012-04-13T23:00:44+00:00 app[web.1]: at play.plugins.PluginCollection.onInvocationException(PluginCollection.java:447) 2012-04-13T23:00:44+00:00 app[web.1]: at play.Invoker$Invocation.onException(Invoker.java:240) 2012-04-13T23:00:44+00:00 app[web.1]: at play.jobs.Job.onException(Job.java:124) 2012-04-13T23:00:44+00:00 app[web.1]: at play.jobs.Job.call(Job.java:163) 2012-04-13T23:00:44+00:00 app[web.1]: at play.jobs.Job$1.call(Job.java:66) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.FutureTask.run(FutureTask.java:166) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$101(ScheduledThreadPoolExecutor.java:165) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:266) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) 2012-04-13T23:00:44+00:00 app[web.1]: at java.lang.Thread.run(Thread.java:636) 2012-04-13T23:00:44+00:00 app[web.1]: Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

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• C++ Compile problem when using Windows - CodeGear

  - by Carlos

  This is a follow-up question to this one i made earlier. Btw thanks Neil Butterworth for you help http://stackoverflow.com/questions/2461977/problem-compiling-c-in-codegear A quick recap. Im currently developing a C++ program for university, I used Netbeans 6.8 on my personal computer (Mac) and all works perfect. When I try them on my windows partition or at the university PC's using CodeGear RAD Studio 2009 & 2010 i was getting a few compile errors which were solved by adding the following header file: #include <string> However now the program does compile but it doesn't run, just a blank console. And am getting the following in the CodeGear event's log: Thread Start: Thread ID: 2024. Process Project1.exe (3280) Process Start: C:\Users\Carlos\Documents\RAD Studio\Projects\Debug\Project1.exe. Base Address: $00400000. Process Project1.exe (3280) Module Load: Project1.exe. Has Debug Info. Base Address: $00400000. Process Project1.exe (3280) Module Load: ntdll.dll. No Debug Info. Base Address: $77E80000. Process Project1.exe (3280) Module Load: KERNEL32.dll. No Debug Info. Base Address: $771C0000. Process Project1.exe (3280) Module Load: KERNELBASE.dll. No Debug Info. Base Address: $75FE0000. Process Project1.exe (3280) Module Load: cc32100.dll. No Debug Info. Base Address: $32A00000. Process Project1.exe (3280) Module Load: USER32.dll. No Debug Info. Base Address: $77980000. Process Project1.exe (3280) Module Load: GDI32.dll. No Debug Info. Base Address: $75F50000. Process Project1.exe (3280) Module Load: LPK.dll. No Debug Info. Base Address: $75AB0000. Process Project1.exe (3280) Module Load: USP10.dll. No Debug Info. Base Address: $76030000. Process Project1.exe (3280) Module Load: msvcrt.dll. No Debug Info. Base Address: $776A0000. Process Project1.exe (3280) Module Load: ADVAPI32.dll. No Debug Info. Base Address: $777D0000. Process Project1.exe (3280) Module Load: SECHOST.dll. No Debug Info. Base Address: $77960000. Process Project1.exe (3280) Module Load: RPCRT4.dll. No Debug Info. Base Address: $762F0000. Process Project1.exe (3280) Module Load: SspiCli.dll. No Debug Info. Base Address: $759F0000. Process Project1.exe (3280) Module Load: CRYPTBASE.dll. No Debug Info. Base Address: $759E0000. Process Project1.exe (3280) Module Load: IMM32.dll. No Debug Info. Base Address: $763F0000. Process Project1.exe (3280) Module Load: MSCTF.dll. No Debug Info. Base Address: $75AD0000. Process Project1.exe (3280) I would really appreciate any help or ideas on how to solve this problem. P.S: In the case anyone wonders why am I sticking with CodeGear is because is the IDE professors use to evaluate our assignments.

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• Looking for best practise for writing a serial device communication app

  - by cdotlister

  I am pretty new to serial comms, but would like advise on how to best achieve a robust application which speak to and listens to a serial device. I have managed to make use of System.IO.SerialPort, and successfully connected to, sent data to and recieved from my device. The way things work is this. My application connects to the Com Port and opens the port.... I then connect my device to the com port, and it detects a connection to the PC, so sends a bit of text. it's really just copyright info, as well as the version of the firmware. I don't do anything with that, except display it in my 'activity' window. The device then waits. I can then query information, but sending a command such as 'QUERY PARAMETER1'. It then replies with something like: 'QUERY PARAMETER1\r\n\r\n76767\r\n\r\n' I then process that. I can then update it by sending 'SET PARAMETER1 12345', and it will reply with 'QUERY PARAMETER1\r\n\r\n12345\r\n\r\n'. All pretty basic. So, what I have done is created a Communication Class. this call is called in it's own thread, and sends data back to the main form... and also allows me to send messages to it. Sending data is easy. Recieving is a bit more tricky. I have employed the use of the datarecieved event, and when ever data comes in, I echo that to my screen. My problem is this: When I send a command, I feel I am being very dodgy in my handling. What I am doing is, lets say I am sending 'QUERY PARAMETER1'. I send the command to the device, I then put 'PARAMETER1' into a global variable, and I do a Thread.Sleep(100). On the data received, I then have a bit of logic that checks the incoming data, and sees if the string CONTAINS the value in the global variable. As the reply may be 'QUERY PARAMETER1\r\n\r\n76767\r\n\r\n', it sees that it contains my parameter, parses the string, and returns the value I am looking for, but placing it into another global variable. My sending method was sleeping for 100ms. It then wakes, and checks the returned global variable. If it has data... then I'm happy, and I process the data. Problem is... if the sleep is too short.. it will fail. And I feel it's flaky.. putting stuff into variables.. then waiting... The other option is to use ReadLine instead, but that's very blocking. So I remove the data received method, and instead... just send the data... then call ReadLine(). That may give me better results. There's no time, except when we connect initially, that data comes from the device, without me requesting it. So, maybe ReadLine will be simpler and safer? Is this known as 'Blocking' reads? Also, can I set a timeout? Hopefully someone can guide me.

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• Jboss 5.1.0: java.lang.LinkageError: loader constraint violation for class javax.sql.DataSource

  - by lawrencexu

  have read quite a lot about this error, the reason is 1) more than one jar containing this class have been include into the classpath, 2)include the jar twice or more, but in my case, this class is jdk class, and I have search no this class have been found under my application. any clue would be very helpful. exception stack: 2012-10-31 14:09:58,319 WARN [org.jboss.detailed.classloader.ClassLoaderManager] (http-0.0.0.0-8080-1:) Unexpected error during load of:javax.sql.DataSource java.lang.LinkageError: loader constraint violation: loader (instance of org/jboss/classloader/spi/base/BaseClassLoader) previously initiated loading for a different type with name "javax/sql/DataSource" at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631) at java.lang.ClassLoader.defineClass(ClassLoader.java:615) at org.jboss.classloader.spi.base.BaseClassLoader.access$200(BaseClassLoader.java:67) at org.jboss.classloader.spi.base.BaseClassLoader$2.run(BaseClassLoader.java:633) at org.jboss.classloader.spi.base.BaseClassLoader$2.run(BaseClassLoader.java:592) at java.security.AccessController.doPrivileged(Native Method) at org.jboss.classloader.spi.base.BaseClassLoader.loadClassLocally(BaseClassLoader.java:591) at org.jboss.classloader.spi.base.BaseClassLoader.loadClassLocally(BaseClassLoader.java:568) at org.jboss.classloader.spi.base.BaseDelegateLoader.loadClass(BaseDelegateLoader.java:135) at org.jboss.classloader.spi.filter.FilteredDelegateLoader.loadClass(FilteredDelegateLoader.java:131) at org.jboss.classloader.spi.base.ClassLoadingTask$ThreadTask.run(ClassLoadingTask.java:455) at org.jboss.classloader.spi.base.ClassLoaderManager.nextTask(ClassLoaderManager.java:267) at org.jboss.classloader.spi.base.ClassLoaderManager.process(ClassLoaderManager.java:166) at org.jboss.classloader.spi.base.BaseClassLoaderDomain.loadClass(BaseClassLoaderDomain.java:287) at org.jboss.classloader.spi.base.BaseClassLoaderDomain.loadClass(BaseClassLoaderDomain.java:1163) at org.jboss.classloader.spi.base.BaseClassLoader.loadClassFromDomain(BaseClassLoader.java:862) at org.jboss.classloader.spi.base.BaseClassLoader.doLoadClass(BaseClassLoader.java:502) at org.jboss.classloader.spi.base.BaseClassLoader.loadClass(BaseClassLoader.java:447) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) at com.lombardrisk.webgui.dwr.ajax_search.UmbrellaNettingFundsSearch.getBranchesByAgreementId(UmbrellaNettingFundsSearch.java:199) at com.lombardrisk.webgui.dwr.ajax_search.UmbrellaNettingFundsSearch.buildConditionOfPrinAndCpty(UmbrellaNettingFundsSearch.java:177) at com.lombardrisk.webgui.dwr.ajax_search.UmbrellaNettingFundsSearch.getFunds(UmbrellaNettingFundsSearch.java:58) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.directwebremoting.impl.ExecuteAjaxFilter.doFilter(ExecuteAjaxFilter.java:34) at org.directwebremoting.impl.DefaultRemoter$1.doFilter(DefaultRemoter.java:428) at org.directwebremoting.impl.DefaultRemoter.execute(DefaultRemoter.java:431) at org.directwebremoting.impl.DefaultRemoter.execute(DefaultRemoter.java:283) at org.directwebremoting.servlet.PlainCallHandler.handle(PlainCallHandler.java:52) at org.directwebremoting.servlet.UrlProcessor.handle(UrlProcessor.java:101) at org.directwebremoting.servlet.DwrServlet.doPost(DwrServlet.java:146) at javax.servlet.http.HttpServlet.service(HttpServlet.java:637) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at com.lombardrisk.webgui.filter.ValidRequestFilter.doFilter(ValidRequestFilter.java:41) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:235) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:183) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:525) at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:95) at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.process(SecurityContextEstablishmentValve.java:126) at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.invoke(SecurityContextEstablishmentValve.java:70) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:158) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.jboss.web.tomcat.service.request.ActiveRequestResponseCacheValve.internalProcess(ActiveRequestResponseCacheValve.java:74) at org.jboss.web.tomcat.service.request.ActiveRequestResponseCacheValve.invoke(ActiveRequestResponseCacheValve.java:47) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:330) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:829) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:599) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:451) at java.lang.Thread.run(Thread.java:662)

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• Insane SmartGWT + GWT situation... Error on instantiating ListGridRecord?

  - by Xandel

  Hi all, I am asking this here in the hope that someone has maybe come across this situation too... I have posted this on the SmartGWT forum: I am having an issue when trying to instantiate a ListGridRecord object on my server side. I am using the ListGrid on the client side, I want to use GWT's RPC to pass back an array of ListGridRecord objects to populate the grid with. I know that SmartGWT is designed to link to a datasource but I want full control over when I populate the grid and this shouldn't be as much of a nightmare as it is to do. I have searched high and low and cannot find anyone complaining about the same thing. The exception however (listed below) has come up (in my search findings) as a possible memory error - where increasing the memory (-Xmx512m argument) has apparently solved the problem. It did not, however, sort out mine. If anyone can shed any light on this I would greatly appreciate it! Here are my details: Developing using Eclipse Galileo on Ubuntu 9.04 (Jaunty) and GWT 2.0.3, I built the initial GWT project using the webAppCreator bundled with the GWT 2.0.3 release and imported the project into Eclipse as described on the GWT Getting Started Page (as using the GWT Eclipse plugin caused even more nightmares when trying to connect to a database - this is apparently due to using the Google App Engine and turning it off as all the posts suggested only causes ClassNotFound exceptions). The line that causes the error is literally: ListGridRecord a = new ListGridRecord(); The error I get is the following: 00:00:25.916 [WARN] Exception while dispatching incoming RPC call com.google.gwt.user.server.rpc.UnexpectedException : Service method 'public abstract java.lang.String za.co.company.product.client.service.EmployeeServi ce.getAllEmployeeAsListGridRecord()' threw an unexpected exception: java.lang.UnsatisfiedLinkError: com.smartgwt.client.util.LogUtil.setJSNIErrorHandl er()V at com.google.gwt.user.server.rpc.RPC.encodeResponseF orFailure(RPC.java:378) at com.google.gwt.user.server.rpc.RPC.invokeAndEncode Response(RPC.java:581) at com.google.gwt.user.server.rpc.RemoteServiceServle t.processCall(RemoteServiceServlet.java:188) at com.google.gwt.user.server.rpc.RemoteServiceServle t.processPost(RemoteServiceServlet.java:224) at com.google.gwt.user.server.rpc.AbstractRemoteServi ceServlet.doPost(AbstractRemoteServiceServlet.java :62) at javax.servlet.http.HttpServlet.service(HttpServlet .java:637) at javax.servlet.http.HttpServlet.service(HttpServlet .java:717) at org.mortbay.jetty.servlet.ServletHolder.handle(Ser vletHolder.java:487) at org.mortbay.jetty.servlet.ServletHandler.handle(Se rvletHandler.java:362) at org.mortbay.jetty.security.SecurityHandler.handle( SecurityHandler.java:216) at org.mortbay.jetty.servlet.SessionHandler.handle(Se ssionHandler.java:181) at org.mortbay.jetty.handler.ContextHandler.handle(Co ntextHandler.java:729) at org.mortbay.jetty.webapp.WebAppContext.handle(WebA ppContext.java:405) at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:152) at org.mortbay.jetty.handler.RequestLogHandler.handle (RequestLogHandler.java:49) at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:152) at org.mortbay.jetty.Server.handle(Server.java:324) at org.mortbay.jetty.HttpConnection.handleRequest(Htt pConnection.java:505) at org.mortbay.jetty.HttpConnection$RequestHandler.co ntent(HttpConnection.java:843) at org.mortbay.jetty.HttpParser.parseNext(HttpParser. java:647) at org.mortbay.jetty.HttpParser.parseAvailable(HttpPa rser.java:211) at org.mortbay.jetty.HttpConnection.handle(HttpConnec tion.java:380) at org.mortbay.io.nio.SelectChannelEndPoint.run(Selec tChannelEndPoint.java:395) at org.mortbay.thread.QueuedThreadPool$PoolThread.run (QueuedThreadPool.java:488) Caused by: java.lang.UnsatisfiedLinkError: com.smartgwt.client.util.LogUtil.setJSNIErrorHandl er()V at com.smartgwt.client.util.LogUtil.setJSNIErrorHandl er(Native Method) at com.smartgwt.client.core.JsObject.(JsObjec t.java:30) at za.co.company.product.server.service.EmployeeServi ceImpl.getAllEmployeeAsListGridRecord(EmployeeServ iceImpl.java:83) at sun.reflect.NativeMethodAccessorImpl.invoke0(Nativ e Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Native MethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(De legatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at com.google.gwt.user.server.rpc.RPC.invokeAndEncode Response(RPC.java:562) at com.google.gwt.user.server.rpc.RemoteServiceServle t.processCall(RemoteServiceServlet.java:188) at com.google.gwt.user.server.rpc.RemoteServiceServle t.processPost(RemoteServiceServlet.java:224) at com.google.gwt.user.server.rpc.AbstractRemoteServi ceServlet.doPost(AbstractRemoteServiceServlet.java :62) at javax.servlet.http.HttpServlet.service(HttpServlet .java:637) at javax.servlet.http.HttpServlet.service(HttpServlet .java:717) at org.mortbay.jetty.servlet.ServletHolder.handle(Ser vletHolder.java:487) at org.mortbay.jetty.servlet.ServletHandler.handle(Se rvletHandler.java:362) at org.mortbay.jetty.security.SecurityHandler.handle( SecurityHandler.java:216) at org.mortbay.jetty.servlet.SessionHandler.handle(Se ssionHandler.java:181) at org.mortbay.jetty.handler.ContextHandler.handle(Co ntextHandler.java:729) at org.mortbay.jetty.webapp.WebAppContext.handle(WebA ppContext.java:405) at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:152) at org.mortbay.jetty.handler.RequestLogHandler.handle (RequestLogHandler.java:49) at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:152) at org.mortbay.jetty.Server.handle(Server.java:324) at org.mortbay.jetty.HttpConnection.handleRequest(Htt pConnection.java:505) at org.mortbay.jetty.HttpConnection$RequestHandler.co ntent(HttpConnection.java:843) at org.mortbay.jetty.HttpParser.parseNext(HttpParser. java:647) at org.mortbay.jetty.HttpParser.parseAvailable(HttpPa rser.java:211) at org.mortbay.jetty.HttpConnection.handle(HttpConnec tion.java:380) at org.mortbay.io.nio.SelectChannelEndPoint.run(Selec tChannelEndPoint.java:395) at org.mortbay.thread.QueuedThreadPool$PoolThread.run (QueuedThreadPool.java:488) Thanks in advance! Xandel

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• easiest and best way to make a server queue java

  - by houlahan

  i have a server at the moment which makes a new thread for every user connected but after about 6 people are on the server for more than 15 mins it tends to flop and give me java heap out of memory error i have 1 thread that checks with a mysql database every 30 seconds to see if any of the users currently logged on have any new messages. what would be the easiest way to implement a server queue? this is the my main method for my server: public class Server { public static int MaxUsers = 1000; //public static PrintStream[] sessions = new PrintStream[MaxUsers]; public static ObjectOutputStream[] sessions = new ObjectOutputStream[MaxUsers]; public static ObjectInputStream[] ois = new ObjectInputStream[MaxUsers]; private static int port = 6283; public static Connection conn; static Toolkit toolkit; static Timer timer; public static void main(String[] args) { try { conn = (Connection) Mysql.getConnection(); } catch (Exception ex) { Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex); } System.out.println("****************************************************"); System.out.println("* *"); System.out.println("* Cloud Server *"); System.out.println("* ©2010 *"); System.out.println("* *"); System.out.println("* Luke Houlahan *"); System.out.println("* *"); System.out.println("* Server Online *"); System.out.println("* Listening On Port " + port + " *"); System.out.println("* *"); System.out.println("****************************************************"); System.out.println(""); mailChecker(); try { int i; ServerSocket s = new ServerSocket(port); for (i = 0; i < MaxUsers; ++i) { sessions[i] = null; } while (true) { try { Socket incoming = s.accept(); boolean found = false; int numusers = 0; int usernum = -1; synchronized (sessions) { for (i = 0; i < MaxUsers; ++i) { if (sessions[i] == null) { if (!found) { sessions[i] = new ObjectOutputStream(incoming.getOutputStream()); ois[i]= new ObjectInputStream(incoming.getInputStream()); new SocketHandler(incoming, i).start(); found = true; usernum = i; } } else { numusers++; } } if (!found) { ObjectOutputStream temp = new ObjectOutputStream(incoming.getOutputStream()); Person tempperson = new Person(); tempperson.setFlagField(100); temp.writeObject(tempperson); temp.flush(); temp = null; tempperson = null; incoming.close(); } else { } } } catch (IOException ex) { System.out.println(1); Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex); } } } catch (IOException ex) { System.out.println(2); Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex); } } public static void mailChecker() { toolkit = Toolkit.getDefaultToolkit(); timer = new Timer(); timer.schedule(new mailCheck(), 0, 10 * 1000); } }

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• Parallel processing via multithreading in Java

  - by Robz

  There are certain algorithms whose running time can decrease significantly when one divides up a task and gets each part done in parallel. One of these algorithms is merge sort, where a list is divided into infinitesimally smaller parts and then recombined in a sorted order. I decided to do an experiment to test whether or not I could I increase the speed of this sort by using multiple threads. I am running the following functions in Java on a Quad-Core Dell with Windows Vista. One function (the control case) is simply recursive: // x is an array of N elements in random order public int[] mergeSort(int[] x) { if (x.length == 1) return x; // Dividing the array in half int[] a = new int[x.length/2]; int[] b = new int[x.length/2+((x.length%2 == 1)?1:0)]; for(int i = 0; i < x.length/2; i++) a[i] = x[i]; for(int i = 0; i < x.length/2+((x.length%2 == 1)?1:0); i++) b[i] = x[i+x.length/2]; // Sending them off to continue being divided mergeSort(a); mergeSort(b); // Recombining the two arrays int ia = 0, ib = 0, i = 0; while(ia != a.length || ib != b.length) { if (ia == a.length) { x[i] = b[ib]; ib++; } else if (ib == b.length) { x[i] = a[ia]; ia++; } else if (a[ia] < b[ib]) { x[i] = a[ia]; ia++; } else { x[i] = b[ib]; ib++; } i++; } return x; } The other is in the 'run' function of a class that extends thread, and recursively creates two new threads each time it is called: public class Merger extends Thread { int[] x; boolean finished; public Merger(int[] x) { this.x = x; } public void run() { if (x.length == 1) { finished = true; return; } // Divide the array in half int[] a = new int[x.length/2]; int[] b = new int[x.length/2+((x.length%2 == 1)?1:0)]; for(int i = 0; i < x.length/2; i++) a[i] = x[i]; for(int i = 0; i < x.length/2+((x.length%2 == 1)?1:0); i++) b[i] = x[i+x.length/2]; // Begin two threads to continue to divide the array Merger ma = new Merger(a); ma.run(); Merger mb = new Merger(b); mb.run(); // Wait for the two other threads to finish while(!ma.finished || !mb.finished) ; // Recombine the two arrays int ia = 0, ib = 0, i = 0; while(ia != a.length || ib != b.length) { if (ia == a.length) { x[i] = b[ib]; ib++; } else if (ib == b.length) { x[i] = a[ia]; ia++; } else if (a[ia] < b[ib]) { x[i] = a[ia]; ia++; } else { x[i] = b[ib]; ib++; } i++; } finished = true; } } It turns out that function that does not use multithreading actually runs faster. Why? Does the operating system and the java virtual machine not "communicate" effectively enough to place the different threads on different cores? Or am I missing something obvious?

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