001 /** 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 package org.apache.xbean.kernel; 018 019 /** 020 * A ServiceContion represents a prerequsite for a service to start or stop. A condition can be added to a service with 021 * the {@link ServiceFactory#addStartCondition(ServiceCondition)} or 022 * {@link ServiceFactory#addStopCondition(ServiceCondition)} methods. 023 * 024 * @author Dain Sundstrom 025 * @version $Id$ 026 * @since 2.0 027 */ 028 public interface ServiceCondition { 029 /** 030 * Initializes the condition. The conition is now allowed reserve unique resources and start threads. 031 * mehtod should never block the thread nor should it throw any exceptions. 032 * </p> 033 * Note: this method is called from within a critical lock within the kernel, so do not block the thread or 034 * call back into the kernel. This method should never throw an exception. 035 * 036 * @param context context information for this condition 037 */ 038 void initialize(ServiceConditionContext context); 039 040 /** 041 * Gets statisfied state of this conditon. Once a condition returns true from this method it is assumed to be satisfied until 042 * destroyed and reinitialized. 043 * </p> 044 * Note: this method is called from within a critical lock within the kernel, so do not block the thread or 045 * call back into the kernel. This method should never throw an exception. 046 * 047 * @return true if this condition is satisfied; false otherwise 048 */ 049 boolean isSatisfied(); 050 051 /** 052 * Destroys the condition. The condition must release all resources and stop any started threads. 053 * </p> 054 * Note: this method is called from within a critical lock within the kernel, so do not block the thread or 055 * call back into the kernel. This method should never throw an exception. 056 */ 057 void destroy(); 058 }