Implement scanInterval configuration and manual scan method

src/main/java/de/ailis/usb4java/Config.java

@@ -16,12 +16,24 @@ final class Config
 {
     /** Base key name for properties. */
     private static final String KEY_BASE = "de.ailis.usb4java.";
+    
+    /** The default USB communication timeout in milliseconds. */
+    private static final int DEFAULT_TIMEOUT = 2500;
+    
+    /** The default scan interval in milliseconds. */
+    private static final int DEFAULT_SCAN_INTERVAL = 500;
 
     /** Key name for USB communication timeout. */
     private static final String TIMEOUT_KEY = KEY_BASE + "timeout";
 
+    /** Key name for USB communication timeout. */
+    private static final String SCAN_INTERVAL_KEY = KEY_BASE + "scanInterval";
+
     /** The timeout for USB communication in milliseconds. */
-    private int timeout = 2500;
+    private int timeout = DEFAULT_TIMEOUT;
+    
+    /** The scan interval in milliseconds. */
+    private int scanInterval = DEFAULT_SCAN_INTERVAL;
 
     /**
      * Constructs new configuration from the specified properties.
@@ -36,6 +48,13 @@ final class Config
         {
             this.timeout = Integer.valueOf(properties.getProperty(TIMEOUT_KEY));
         }
+
+        // Read the USB device scan interval
+        if (properties.containsKey(SCAN_INTERVAL_KEY))
+        {
+            this.scanInterval = Integer.valueOf(properties.getProperty(
+                SCAN_INTERVAL_KEY));
+        }
     }
 
     /**
@@ -47,4 +66,14 @@ final class Config
     {
         return this.timeout;
     }
+
+    /**
+     * Returns the scan interval in milliseconds.
+     *
+     * @return The scan interval in milliseconds.
+     */
+    public int getScanInterval()
+    {
+        return this.scanInterval;
+    }
 }

src/main/java/de/ailis/usb4java/DeviceManager.java

@@ -30,9 +30,6 @@ import de.ailis.usb4java.libusb.LibUsbException;
  */
 final class DeviceManager
 {
-    /** The scan interval in milliseconds. */
-    private static final int DEFAULT_SCAN_INTERVAL = 500;
-
     /** The logger. */
     private static final Logger LOG = Logger.getLogger(DeviceManager.class
         .getName());
@@ -46,6 +43,9 @@ final class DeviceManager
     /** If scanner already scanned for devices. */
     private boolean scanned = false;
 
+    /** The scan interval in milliseconds. */
+    private final int scanInterval;
+
     /** The currently connected devices. */
     private final Map<DeviceId, AbstractDevice> devices = Collections
         .synchronizedMap(new HashMap<DeviceId, AbstractDevice>());
@@ -55,13 +55,17 @@ final class DeviceManager
      * 
      * @param rootHub
      *            The root hub. Must not be null.
+     * @param scanInterval
+     *            The scan interval in milliseconds.
      * @throws UsbException
      *             When USB initialization fails.
      */
-    DeviceManager(final RootHub rootHub) throws UsbException
+    DeviceManager(final RootHub rootHub, final int scanInterval)
+        throws UsbException
     {
         if (rootHub == null)
             throw new IllegalArgumentException("rootHub must be set");
+        this.scanInterval = scanInterval;
         this.rootHub = rootHub;
         this.context = new Context();
         final int result = LibUsb.init(this.context);
@@ -77,7 +81,7 @@ final class DeviceManager
     {
         LibUsb.exit(this.context);
     }
-
+    
     /**
      * Creates a device ID from the specified device.
      * 
@@ -266,7 +270,7 @@ final class DeviceManager
     /**
      * Scans the USB busses for new or removed devices.
      */
-    public void scan()
+    public synchronized void scan()
     {
         scan(this.rootHub);
         this.scanned = true;
@@ -330,6 +334,10 @@ final class DeviceManager
      */
     public void start()
     {
+        // Do not start the scan thread when interval is set to 0
+        final int scanInterval = this.scanInterval;
+        if (scanInterval == 0) return;
+        
         final Thread thread = new Thread(new Runnable()
         {
             @Override
@@ -339,7 +347,7 @@ final class DeviceManager
                 {
                     try
                     {
-                        Thread.sleep(DEFAULT_SCAN_INTERVAL);
+                        Thread.sleep(scanInterval);
                     }
                     catch (final InterruptedException e)
                     {

src/main/java/de/ailis/usb4java/Services.java

@@ -40,7 +40,7 @@ public final class Services implements UsbServices
     private final RootHub rootHub;
 
     /** The USB device scanner. */
-    private final DeviceManager deviceScanner;
+    private final DeviceManager deviceManager;
 
     /** If devices should be scanned by hierarchy. */
     private final Config config;
@@ -58,14 +58,15 @@ public final class Services implements UsbServices
         this.config = new Config(UsbHostManager.getProperties());
         Loader.load();
         this.rootHub = new RootHub();
-        this.deviceScanner = new DeviceManager(this.rootHub);
-        this.deviceScanner.start();
+        this.deviceManager = new DeviceManager(this.rootHub, 
+            this.config.getScanInterval());
+        this.deviceManager.start();
     }
 
     @Override
     public UsbHub getRootUsbHub()
     {
-        this.deviceScanner.firstScan();
+        this.deviceManager.firstScan();
         return this.rootHub;
     }
 
@@ -153,4 +154,12 @@ public final class Services implements UsbServices
                 + e, e);
         }
     }
+    
+    /**
+     * Manually scans for USB device connection changes.
+     */
+    public void scan()
+    {
+        this.deviceManager.scan();
+    }
 }

src/site/apt/configuration.apt.vm

@@ -29,3 +29,23 @@ javax.usb.services = de.ailis.usb4java.Services
 +----+
 de.ailis.usb4java.timeout = 250
 +----+
+
+
+* Scan interval
+
+  The default USB device scan interval of <usb4java> is 500 milliseconds. To
+  change this to 1000 milliseconds for example add this to the properties file:
+
++----+
+de.ailis.usb4java.scanInterval = 1000
++----+
+
+  When you set this interval to 0 then <usb4java> only scans once during
+  application startup. If you want to trigger a manual device <scan> you can
+  do it by calling the scan method on the USB services class (Must be casted
+  to the <usb4java> implementation, because this is not a javax.usb feature:
+
++----+
+((de.ailis.usb4java.Services) UsbHostManager.getUsbServices()).scan();
++----+
+