Java core dump when terminating Webcam Capture process

fixes #13

Author: sarxos

webcam-capture/src/example/java/com/github/sarxos/webcam/WebcamViewerExample.java

@@ -8,11 +8,6 @@
 import javax.swing.JPanel;
 import javax.swing.SwingUtilities;
 
-import com.github.sarxos.webcam.Webcam;
-import com.github.sarxos.webcam.WebcamEvent;
-import com.github.sarxos.webcam.WebcamListener;
-import com.github.sarxos.webcam.WebcamPanel;
-
 
 /**
  * Proof of concept of how to handle webcam video stream from Java
@@ -78,6 +73,10 @@ public void webcamClosed(WebcamEvent we) {
 		pack();
 	}
 
+	@Override
+	public void webcamDisposed(WebcamEvent we) {
+	}
+
 	@Override
 	public void windowActivated(WindowEvent e) {
 		// TODO Auto-generated method stub
@@ -109,4 +108,5 @@ public void windowDeiconified(WindowEvent e) {
 	public void windowIconified(WindowEvent e) {
 		view.pause();
 	}
+
 }

webcam-capture/src/main/java/com/github/sarxos/webcam/Webcam.java

@@ -68,7 +68,9 @@ public void run() {
 
 	private ShutdownHook hook = null;
 	private WebcamDevice device = null;
-	private boolean open = false;
+
+	private volatile boolean open = false;
+	private volatile boolean disposed = false;
 
 	/**
 	 * Webcam class.
@@ -264,12 +266,19 @@ public void setViewSize(Dimension size) {
 	 * 
 	 * @return Captured image
 	 */
-	public synchronized BufferedImage getImage() {
-		if (!open) {
-			LOG.debug("Try to get image on closed webcam, opening it automatically");
-			open();
+	public BufferedImage getImage() {
+
+		if (disposed) {
+			return null;
+		}
+
+		synchronized (this) {
+			if (!open) {
+				LOG.debug("Try to get image on closed webcam, opening it automatically");
+				open();
+			}
+			return device.getImage();
 		}
-		return device.getImage();
 	}
 
 	/**
@@ -290,15 +299,13 @@ public static List<Webcam> getWebcams() {
 				driver = new WebcamDefaultDriver();
 			}
 
-			List<WebcamDevice> devices = driver.getDevices();
+			for (WebcamDevice device : driver.getDevices()) {
+				webcams.add(new Webcam(device));
+			}
 
 			if (deallocOnTermSignal) {
 				LOG.warn("Automated deallocation on TERM signal is enabled!");
-				WebcamDeallocator.store(devices.toArray(new WebcamDevice[devices.size()]));
-			}
-
-			for (WebcamDevice device : devices) {
-				webcams.add(new Webcam(device));
+				WebcamDeallocator.store(webcams.toArray(new Webcam[webcams.size()]));
 			}
 
 			if (LOG.isInfoEnabled()) {
@@ -471,8 +478,23 @@ public WebcamDevice getDevice() {
 	 * used any more and reinstantiation is required.
 	 */
 	protected void dispose() {
-		device.close();
-		device.dispose();
+
+		open = false;
+		disposed = true;
+
+		WebcamEvent we = new WebcamEvent(this);
+		for (WebcamListener l : listeners) {
+			try {
+				l.webcamDisposed(we);
+			} catch (Exception e) {
+				LOG.error(String.format("Notify webcam disposed, exception when calling %s listener", l.getClass()), e);
+			}
+		}
+
+		synchronized (this) {
+			device.close();
+			device.dispose();
+		}
 	}
 
 	/**

webcam-capture/src/main/java/com/github/sarxos/webcam/WebcamDeallocator.java

@@ -7,7 +7,6 @@
 import java.util.Observer;
 
 
-
 /**
  * Deallocator which goal is to release all devices resources when SIGTERM
  * signal is detected.
@@ -16,7 +15,7 @@
  */
 class WebcamDeallocator implements Observer {
 
-	private WebcamDevice[] devices = null;
+	private Webcam[] webcams = null;
 	private WebcamSignalHandler handler = new WebcamSignalHandler();
 
 	/**
@@ -25,9 +24,9 @@ class WebcamDeallocator implements Observer {
 	 * 
 	 * @param devices the devices to be stored in deallocator
 	 */
-	private WebcamDeallocator(WebcamDevice[] devices) {
+	private WebcamDeallocator(Webcam[] devices) {
 		if (devices != null && devices.length > 0) {
-			this.devices = devices;
+			this.webcams = devices;
 			this.handler.listen("TERM", this);
 		}
 	}
@@ -37,15 +36,15 @@ private WebcamDeallocator(WebcamDevice[] devices) {
 	 * 
 	 * @param devices the devices array to be stored by deallocator
 	 */
-	protected static final void store(WebcamDevice[] devices) {
+	protected static final void store(Webcam[] devices) {
 		new WebcamDeallocator(devices);
 	}
 
 	@Override
 	public void update(Observable observable, Object object) {
-		for (WebcamDevice device : devices) {
+		for (Webcam device : webcams) {
 			try {
-				device.close();
+				device.dispose();
 			} catch (Throwable t) {
 				caugh(t);
 			}

webcam-capture/src/main/java/com/github/sarxos/webcam/WebcamListener.java

@@ -21,4 +21,10 @@ public interface WebcamListener {
 	 */
 	public void webcamClosed(WebcamEvent we);
 
+	/**
+	 * Webcam has been disposed
+	 * 
+	 * @param we a webcam event
+	 */
+	public void webcamDisposed(WebcamEvent we);
 }

webcam-capture/src/main/java/com/github/sarxos/webcam/WebcamPanel.java

@@ -313,6 +313,11 @@ public void webcamClosed(WebcamEvent we) {
 		}
 	}
 
+	@Override
+	public void webcamDisposed(WebcamEvent we) {
+		webcamClosed(we);
+	}
+
 	/**
 	 * Open webcam and start rendering.
 	 */

webcam-capture/src/main/java/com/github/sarxos/webcam/WebcamStreamer.java

@@ -247,10 +247,15 @@ public void webcamOpen(WebcamEvent we) {
 	public void webcamClosed(WebcamEvent we) {
 	}
 
+	@Override
+	public void webcamDisposed(WebcamEvent we) {
+	}
+
 	public static void main(String[] args) throws InterruptedException {
 		new WebcamStreamer(8081, Webcam.getDefault(), 0.5, true);
 		do {
 			Thread.sleep(1000);
 		} while (true);
 	}
+
 }

webcam-capture/src/main/java/com/github/sarxos/webcam/ds/buildin/WebcamDefaultDevice.java

@@ -109,13 +109,20 @@ public class WebcamDefaultDevice implements WebcamDevice {
 	private volatile boolean opening = false;
 	private volatile boolean disposed = false;
 
+	private String name = null;
+	private String id = null;
+	private String fullname = null;
+
 	protected WebcamDefaultDevice(Device device) {
 		this.device = device;
+		this.name = device.getNameStr();
+		this.id = device.getIdentifierStr();
+		this.fullname = String.format("%s %s", this.name, this.id);
 	}
 
 	@Override
 	public String getName() {
-		return String.format("%s %s", device.getNameStr(), device.getIdentifierStr());
+		return fullname;
 	}
 
 	@Override
@@ -136,8 +143,13 @@ public void setSize(Dimension size) {
 	@Override
 	public BufferedImage getImage() {
 
+		if (disposed) {
+			throw new WebcamException("Cannot get image since device is already disposed");
+		}
+
 		if (!open) {
-			throw new WebcamException("Cannot get image when webcam device is not open");
+			LOG.error("Cannot get image when device is closed");
+			return null;
 		}
 
 		frameTask.nextFrame();
@@ -163,8 +175,7 @@ public BufferedImage getImage() {
 	public void open() {
 
 		if (disposed) {
-			LOG.warn("Cannot open webcam when it's already disposed");
-			return;
+			throw new WebcamException("Cannot open webcam when device it's already disposed");
 		}
 
 		synchronized (device) {
@@ -223,6 +234,11 @@ public void open() {
 				frameTask.nextFrame();
 				imageTask.getImage(size);
 
+				if (disposed) {
+					opening = false;
+					return;
+				}
+
 				try {
 					Thread.sleep(1000);
 				} catch (InterruptedException e) {
@@ -257,6 +273,10 @@ public void close() {
 
 	@Override
 	public void dispose() {
+		if (disposed) {
+			return;
+		}
+		close();
 		disposed = true;
 	}