Merge pull request #329 from maiksd/shutdownHook

New class ERXShutdownHook to use in place of plain Threads with Runtime.addShutdownHook

Frameworks/Core/ERExtensions/Sources/er/extensions/appserver/ERXApplication.java

@@ -1064,6 +1064,7 @@ public static void setup(String[] argv) {
 		ERXConfigurationManager.defaultManager().setCommandLineArguments(argv);
 		ERXFrameworkPrincipal.setUpFrameworkPrincipalClass(ERXExtensions.class);
 		// NSPropertiesCoordinator.loadProperties();
+		ERXShutdownHook.useMe();
 	}
 
 	/**

Frameworks/Core/ERExtensions/Sources/er/extensions/appserver/ERXShutdownHook.java

@@ -0,0 +1,109 @@
+
+package er.extensions.appserver;
+
+import java.util.HashSet;
+import java.util.Set;
+
+
+/**
+ * <p>Use this to register shutdown hooks instead of directly using Runtime.addShutdownHook().
+ * The net effect is that there will be a specific log file entry AFTER all other shutdown
+ * hooks have completed, notifying a watching user that shutdown of the application has
+ * indeed completed, which says:</p>
+ * 
+ * <tt>APPLICATION SHUTDOWN SEQUENCE COMPLETE</tt>
+ * 
+ * <p>on a single line. After you see this line in the application's log file, you can be
+ * pretty sure that the process is indeed terminated. This notification works even if
+ * there are no other shutdown hooks registered, if you ensure that this class is
+ * loaded at all, e.g. by calling the no-op {@link useMe} method somewhere
+ * ({@link ERXApplication} does this for you if you extend that).</p>
+ * 
+ * <p>Usage (e.g. in your Application class constructor):</p>
+ * 
+ * <p><blockquote><pre>
+ * new ERXShutdownHook() {
+ *     {@literal @}Override
+ *     public void hook() {
+ *         // do something
+ *     }
+ * };
+ * </pre></blockquote></p>
+ *
+ * @author Maik Musall, [email protected]
+ *
+ */
+public abstract class ERXShutdownHook extends Thread {
+
+	static final Set<ERXShutdownHook> ALL_HOOKS = new HashSet<ERXShutdownHook>();
+
+	static {
+		Runtime.getRuntime().addShutdownHook( new Thread() {
+			@Override
+			public void run() {
+				try {
+					synchronized( ALL_HOOKS ) {
+						while( ALL_HOOKS.size() > 0 ) {
+							// Use System.out to minimize dependencies
+							System.out.println( "ShutdownHook waiting for " + ALL_HOOKS.size() + " hook" + (ALL_HOOKS.size() > 1 ? "s" : "") + " to complete" );
+							ALL_HOOKS.wait();
+						}
+						System.out.println( "APPLICATION SHUTDOWN SEQUENCE COMPLETE" );
+					}
+				} catch( Exception e ) {
+					e.printStackTrace();
+				}
+			}
+		} );
+	}
+
+	private String name;
+
+
+	/**
+	 * Call this in your app constructor if you have no other shutdown hooks. If you don't call
+	 * anything, this class will not be loaded at all and won't work.
+	 * 
+	 * {@link ERXApplication} calls this, so no need to do this if you're extending that.
+	 */
+	public static void useMe() {
+		// do nothing
+	}
+
+	/**
+	 * Construct a new nameless shutdown hook and register it.
+	 */
+	public ERXShutdownHook() {
+		Runtime.getRuntime().addShutdownHook( this );
+		ALL_HOOKS.add( this );
+	}
+
+	/**
+	 * Construct a new named shutdown hook and register it.
+	 * @param hookName hook name
+	 */
+	public ERXShutdownHook( String hookName ) {
+		this();
+		this.name = hookName;
+	}
+
+	@Override
+	public final void run() {
+		try {
+			if( name != null ) System.out.println( "ERXShutdownHook " + name + " launched" );
+			hook();
+			if( name != null ) System.out.println( "ERXShutdownHook " + name + " completed" );
+			synchronized( ALL_HOOKS ) {
+				ALL_HOOKS.remove( this );
+				ALL_HOOKS.notify();
+			}
+		} catch( Exception e ) {
+			e.printStackTrace();
+		}
+	}
+
+	/**
+	 * This is where you implement what is supposed to be run at shutdown time.
+	 */
+	abstract public void hook();
+}