| /* |
| * |
| * 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 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 {@link 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 all {@link LogActor}s |
| */ |
| public static void removeAll() |
| { |
| Stack<LogActor> stack = _currentActor.get(); |
| stack.clear(); |
| } |
| |
| /** |
| * Remove the current {@link 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 {@link LogActor}s. |
| * |
| * @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; |
| } |
| } |