1 files changed, 121 insertions, 0 deletions
diff --git a/trunk/qpid/java/broker/src/main/java/org/apache/qpid/server/logging/actors/CurrentActor.java b/trunk/qpid/java/broker/src/main/java/org/apache/qpid/server/logging/actors/CurrentActor.java
new file mode 100644
index 0000000000..3d31a705fe
--- /dev/null
+++ b/trunk/qpid/java/broker/src/main/java/org/apache/qpid/server/logging/actors/CurrentActor.java
@@ -0,0 +1,121 @@
+/*
+ *
+ * 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.qpid.server.logging.actors;
+
+import org.apache.qpid.server.logging.LogActor;
+import org.apache.qpid.server.logging.LogSubject;
+import org.apache.qpid.server.logging.LogMessage;
+import org.apache.qpid.server.logging.RootMessageLogger;
+
+import java.util.EmptyStackException;
+import java.util.Stack;
+
+/**
+ * The CurrentActor is a ThreadLocal wrapper that allows threads in the broker
+ * to retrieve an actor to perform logging. This approach is used so for two
+ * reasons:
+ * 1) We do not have to pass a logging actor around the system
+ * 2) We can set new actors at the point we have enough information. i.e.
+ * - Set a low level ConnectionActor when processing bytes from the wire.
+ * - Set a ChannelActor when we are processing the frame
+ * - Set a SubscriptionActor when we are handling the subscription.
+ * <p/>
+ * The code performing the logging need not worry about what type of actor is
+ * currently set so can perform its logging. The resulting log entry though will
+ * contain customised details from the the currently set Actor.
+ * <p/>
+ * The Actor model also allows the pre-creation of fixed messages so the
+ * performance impact of the additional logging data is minimised.
+ * <p/>
+ * This class does not perform any checks to ensure that there is an Actor set
+ * when calling remove or get. As a result the application developer must ensure
+ * that they have called set before they attempt to use the actor via get or
+ * remove the set actor.
+ * <p/>
+ * The checking of the return via get should not be done as the logging is
+ * desired. It is preferable to cause the NullPointerException to highlight the
+ * programming error rather than miss a log message.
+ * <p/>
+ * The same is true for the remove. A NPE will occur if no set has been called
+ * highlighting the programming error.
+ */
+public class CurrentActor
+{
+    /** The ThreadLocal variable with initialiser */
+    private static final ThreadLocal<Stack<LogActor>> _currentActor = new ThreadLocal<Stack<LogActor>>()
+    {
+        // Initialise the CurrentActor to be an empty List
+        protected Stack<LogActor> initialValue()
+        {
+            return new Stack<LogActor>();
+        }
+    };
+
+    private static LogActor _defaultActor;
+
+    /**
+     * Set a new LogActor to be the Current Actor
+     * <p/>
+     * This pushes the Actor in to the LIFO Queue
+     *
+     * @param actor The new LogActor
+     */
+    public static void set(LogActor actor)
+    {
+        Stack<LogActor> stack = _currentActor.get();
+        stack.push(actor);
+    }
+
+    /**
+     * Remove the current LogActor.
+     * <p/>
+     * Calling remove without calling set will result in an EmptyStackException.
+     */
+    public static void remove()
+    {
+        Stack<LogActor> stack = _currentActor.get();
+        stack.pop();
+    }
+
+    /**
+     * Return the current head of the list of LogActors.
+     * <p/>
+     * If there has been no set call then this will return Null.
+     *
+     * @return Current LogActor
+     */
+    public static LogActor get()
+    {
+        try
+        {
+            return _currentActor.get().peek();
+        }
+        catch (EmptyStackException ese)
+        {
+            return _defaultActor;
+        }
+    }
+
+    public static void setDefault(LogActor defaultActor)
+    {
+        _defaultActor = defaultActor;
+    }
+}