FELIX-1962 Provide a ProxyListener analogous to the ProxyServlet to be called by the actual listener registered with the servlet container and to forward the events to the registered listeners.

git-svn-id: https://svn.apache.org/repos/asf/felix/trunk@1057094 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/http/proxy/src/main/java/org/apache/felix/http/proxy/DispatcherTracker.java b/http/proxy/src/main/java/org/apache/felix/http/proxy/DispatcherTracker.java
index 7552dc9..9901575 100644
--- a/http/proxy/src/main/java/org/apache/felix/http/proxy/DispatcherTracker.java
+++ b/http/proxy/src/main/java/org/apache/felix/http/proxy/DispatcherTracker.java
@@ -27,11 +27,11 @@
 public final class DispatcherTracker
     extends ServiceTracker
 {
-    private final static String DEFAULT_FILTER = "(http.felix.dispatcher=*)";
+    final static String DEFAULT_FILTER = "(http.felix.dispatcher=*)";
 
     private final ServletConfig config;
     private HttpServlet dispatcher;
-    
+
     public DispatcherTracker(BundleContext context, String filter, ServletConfig config)
         throws Exception
     {
diff --git a/http/proxy/src/main/java/org/apache/felix/http/proxy/ProxyListener.java b/http/proxy/src/main/java/org/apache/felix/http/proxy/ProxyListener.java
new file mode 100644
index 0000000..95b7760
--- /dev/null
+++ b/http/proxy/src/main/java/org/apache/felix/http/proxy/ProxyListener.java
@@ -0,0 +1,192 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.felix.http.proxy;
+
+import java.util.EventListener;
+
+import javax.servlet.ServletContext;
+import javax.servlet.ServletContextEvent;
+import javax.servlet.ServletContextListener;
+import javax.servlet.http.HttpSessionAttributeListener;
+import javax.servlet.http.HttpSessionBindingEvent;
+import javax.servlet.http.HttpSessionEvent;
+import javax.servlet.http.HttpSessionListener;
+
+import org.osgi.framework.BundleContext;
+import org.osgi.framework.Constants;
+import org.osgi.framework.Filter;
+import org.osgi.framework.InvalidSyntaxException;
+import org.osgi.framework.ServiceReference;
+import org.osgi.util.tracker.ServiceTracker;
+
+/**
+ * The <code>ProxyListener</code> implements a Servlet API listener for HTTP
+ * Session related events. These events are provided by the servlet container
+ * and forwarded to the event dispatcher.
+ */
+public class ProxyListener implements HttpSessionAttributeListener, HttpSessionListener, ServletContextListener
+{
+
+    private ServletContext servletContext;
+
+    private ServiceTracker eventDispatcherTracker;
+
+    private HttpSessionListener sessionDispatcher;
+
+    private HttpSessionAttributeListener attributeDispatcher;
+
+    // ---------- ServletContextListener
+
+    public void contextInitialized(final ServletContextEvent sce)
+    {
+        this.servletContext = sce.getServletContext();
+    }
+
+    public void contextDestroyed(final ServletContextEvent sce)
+    {
+        if (this.eventDispatcherTracker != null)
+        {
+            this.eventDispatcherTracker.close();
+            this.eventDispatcherTracker = null;
+        }
+        this.servletContext = null;
+    }
+
+    // ---------- HttpSessionListener
+
+    public void sessionCreated(final HttpSessionEvent se)
+    {
+        final HttpSessionListener sessionDispatcher = getSessionDispatcher();
+        if (sessionDispatcher != null)
+        {
+            sessionDispatcher.sessionCreated(se);
+        }
+    }
+
+    public void sessionDestroyed(final HttpSessionEvent se)
+    {
+        final HttpSessionListener sessionDispatcher = getSessionDispatcher();
+        if (sessionDispatcher != null)
+        {
+            sessionDispatcher.sessionDestroyed(se);
+        }
+    }
+
+    // ---------- HttpSessionAttributeListener
+
+    public void attributeAdded(final HttpSessionBindingEvent se)
+    {
+        final HttpSessionAttributeListener attributeDispatcher = getAttributeDispatcher();
+        if (attributeDispatcher != null)
+        {
+            attributeDispatcher.attributeAdded(se);
+        }
+    }
+
+    public void attributeRemoved(final HttpSessionBindingEvent se)
+    {
+        final HttpSessionAttributeListener attributeDispatcher = getAttributeDispatcher();
+        if (attributeDispatcher != null)
+        {
+            attributeDispatcher.attributeRemoved(se);
+        }
+    }
+
+    public void attributeReplaced(final HttpSessionBindingEvent se)
+    {
+        final HttpSessionAttributeListener attributeDispatcher = getAttributeDispatcher();
+        if (attributeDispatcher != null)
+        {
+            attributeDispatcher.attributeReplaced(se);
+        }
+    }
+
+    // ---------- internal
+
+    private Object getDispatcher()
+    {
+        if (this.eventDispatcherTracker == null)
+        {
+            // the bundle context may or may not be already provided;
+            // if not we cannot access the dispatcher yet
+            Object bundleContextAttr = this.servletContext.getAttribute(BundleContext.class.getName());
+            if (!(bundleContextAttr instanceof BundleContext))
+            {
+                return null;
+            }
+
+            try
+            {
+                BundleContext bundleContext = (BundleContext) bundleContextAttr;
+                Filter filter = createFilter(bundleContext, null);
+                this.eventDispatcherTracker = new ServiceTracker(bundleContext, filter, null)
+                {
+                    public void removedService(ServiceReference reference, Object service)
+                    {
+                        ProxyListener.this.sessionDispatcher = null;
+                        ProxyListener.this.attributeDispatcher = null;
+                        super.removedService(reference, service);
+                    }
+                };
+                this.eventDispatcherTracker.open();
+            }
+            catch (InvalidSyntaxException e)
+            {
+                // not expected for our simple filter
+            }
+
+        }
+        return this.eventDispatcherTracker.getService();
+    }
+
+    private HttpSessionListener getSessionDispatcher()
+    {
+        if (this.sessionDispatcher == null)
+        {
+            final Object dispatcher = getDispatcher();
+            if (dispatcher instanceof HttpSessionListener)
+            {
+                this.sessionDispatcher = (HttpSessionListener) dispatcher;
+            }
+        }
+        return this.sessionDispatcher;
+    }
+
+    private HttpSessionAttributeListener getAttributeDispatcher()
+    {
+        if (this.attributeDispatcher == null)
+        {
+            final Object dispatcher = getDispatcher();
+            if (dispatcher instanceof HttpSessionAttributeListener)
+            {
+                this.attributeDispatcher = (HttpSessionAttributeListener) dispatcher;
+            }
+        }
+        return this.attributeDispatcher;
+    }
+
+    private static Filter createFilter(BundleContext context, String filter) throws InvalidSyntaxException
+    {
+        StringBuffer str = new StringBuffer();
+        str.append("(&(").append(Constants.OBJECTCLASS).append("=");
+        str.append(EventListener.class.getName()).append(")");
+        str.append(filter != null ? filter : DispatcherTracker.DEFAULT_FILTER).append(")");
+        return context.createFilter(str.toString());
+    }
+}