| /******************************************************************************* |
| * 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.sling.scripting.sightly.js.impl.async; |
| |
| import java.util.ArrayList; |
| import java.util.List; |
| |
| /** |
| * Simple container for asynchronously provided values |
| */ |
| public class AsyncContainer { |
| |
| private Object value; |
| private boolean completed; |
| private List<UnaryCallback> callbacks = new ArrayList<UnaryCallback>(); |
| |
| /** |
| * Add a listener that will receive the value in this container when it will |
| * be filled. If the container already has a value, the callback is called |
| * immediately. |
| * @param unaryCallback the callback that will receive the result |
| */ |
| public void addListener(UnaryCallback unaryCallback) { |
| callbacks.add(unaryCallback); |
| if (completed) { |
| notifyListener(unaryCallback); |
| } |
| } |
| |
| /** |
| * Get the result of this holder |
| * @return the holder result |
| * @throws java.util.NoSuchElementException if the result has not yet been set |
| */ |
| public Object getResult() { |
| return value; |
| } |
| |
| /** |
| * Check whether the container was completed with a value |
| * @return the completion status |
| */ |
| public boolean isCompleted() { |
| return completed; |
| } |
| |
| /** |
| * Complete this async container with a value |
| * @param value the result value |
| * @throws java.lang.IllegalStateException if the container has been previously filled |
| */ |
| public void complete(Object value) { |
| if (completed) { |
| throw new IllegalStateException("Value was already completed"); |
| } |
| completed = true; |
| this.value = value; |
| for (UnaryCallback callback : callbacks) { |
| notifyListener(callback); |
| } |
| } |
| |
| /** |
| * Create a callback that will complete this container |
| * @return the completion callback |
| */ |
| public UnaryCallback createCompletionCallback() { |
| return new UnaryCallback() { |
| @Override |
| public void invoke(Object arg) { |
| complete(arg); |
| } |
| }; |
| } |
| |
| private void notifyListener(UnaryCallback unaryCallback) { |
| unaryCallback.invoke(value); |
| } |
| } |