Added support for callbacks when changes in I2PAppContext properties occur.

core/java/src/net/i2p/I2PAppContext.java

@@ -27,11 +27,13 @@ import net.i2p.util.Clock;
 import net.i2p.util.ConcurrentHashSet;
 import net.i2p.util.FileUtil;
 import net.i2p.util.FortunaRandomSource;
+import net.i2p.util.I2PProperties;
 import net.i2p.util.KeyRing;
 import net.i2p.util.LogManager;
 //import net.i2p.util.PooledRandomSource;
 import net.i2p.util.RandomSource;
 import net.i2p.util.SecureDirectory;
+import net.i2p.util.I2PProperties.I2PPropertyCallback;
 
 /**
  * <p>Provide a base scope for accessing singletons that I2P exposes.  Rather than
@@ -62,7 +64,7 @@ public class I2PAppContext {
     /** the context that components without explicit root are bound */
     protected static I2PAppContext _globalAppContext;
     
-    private Properties _overrideProps;
+    private I2PProperties _overrideProps;
     
     private StatManager _statManager;
     private SessionKeyManager _sessionKeyManager;
@@ -165,7 +167,7 @@ public class I2PAppContext {
                     _globalAppContext = this;
             }
         }
-        _overrideProps = envProps;
+        _overrideProps = new I2PProperties(envProps);
         _statManager = null;
         _sessionKeyManager = null;
         _namingService = null;
@@ -478,6 +480,27 @@ public class I2PAppContext {
         return names;
     }
     
+    /**
+     * Modify the configuration attributes of this context, changing
+     * one of the properties provided during the context construction.
+     * @param propName The name of the property.
+     * @param value The new value for the property.
+     */
+    public void setProperty(String propName, String value) {
+    	if(_overrideProps != null) {
+    		_overrideProps.setProperty(propName, value);
+    	}
+    }
+    
+    /**
+     * Add a callback, which will fire upon changes in the property
+     * given in the specific callback.
+     * @param callback The implementation of the callback.
+     */
+    public void addPropertyCallback(I2PPropertyCallback callback) {
+    	_overrideProps.addCallBack(callback);
+    }
+    
     /**
      * The statistics component with which we can track various events
      * over time.

core/java/src/net/i2p/util/I2PProperties.java

@@ -0,0 +1,57 @@
+package net.i2p.util;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Properties;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+/**
+ * This class contains a number of properties ((key,value)-pairs).
+ * Additionally, it adds the possibility for callbacks,
+ * to allow immediate response to changing properties.
+ * @author Mathiasdm
+ *
+ */
+public class I2PProperties extends Properties {
+	
+	/**
+	 * Keep a list of callbacks to contact the interested parties
+	 * that want to know about property changes.
+	 * @todo Use a map of lists, so we don't need to loop over all the callbacks on every change.
+	 */
+	private final List<I2PPropertyCallback> _callbacks = new CopyOnWriteArrayList<I2PPropertyCallback>();
+
+	public I2PProperties() {
+		super();
+	}
+
+	public I2PProperties(Properties defaults) {
+		super(defaults);
+	}
+	
+	public void addCallBack(I2PPropertyCallback callback) {
+		_callbacks.add(callback);
+	}
+	
+	public void removeCallBack(I2PPropertyCallback callback) {
+		_callbacks.remove(callback);
+	}
+	
+	public Object setProperty(String key, String value) {
+		Object returnValue = super.setProperty(key, value);
+		for(I2PPropertyCallback callback: _callbacks) {
+			if(callback.getPropertyKey().equals(key)) {
+				callback.propertyChanged(key, value);
+			}
+		}
+		return returnValue;
+	}
+	
+	public interface I2PPropertyCallback {
+		
+		public void propertyChanged(String key, String value);
+		
+		public String getPropertyKey();
+	}
+
+}