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     * This condition that requires another service be in the STOPPED state to be satisfied.
021     *
022     * @author Dain Sundstrom
023     * @version $Id$
024     * @since 2.0
025     */
026    public class StoppedServiceCondition implements ServiceCondition {
027        private final ServiceName dependency;
028        private final DependencyServiceMonitor serviceMonitor = new DependencyServiceMonitor();
029    
030        private ServiceConditionContext context;
031        private boolean satisfied = true;
032    
033        /**
034         * Creates a condition that requires the specified service be in the STOPPED state to be satisfied.
035         *
036         * @param dependency the service that must be stopped
037         */
038        public StoppedServiceCondition(ServiceName dependency) {
039            if (dependency == null) throw new NullPointerException("dependency is null");
040            this.dependency = dependency;
041        }
042    
043        /**
044         * {@inheritDoc}
045         */
046        public synchronized void initialize(ServiceConditionContext context) {
047            if (context == null) throw new NullPointerException("context is null");
048    
049            // if we have no been destroyed, destroy not
050            if (this.context != null) {
051                destroy();
052            }
053    
054            this.context = context;
055    
056            satisfied = false;
057            context.getKernel().addServiceMonitor(serviceMonitor, dependency);
058        }
059    
060        /**
061         * {@inheritDoc}
062         */
063        public synchronized boolean isSatisfied() {
064            if (context == null) {
065                // we are not initialized so default to true
066                return true;
067            }
068    
069            if (!satisfied) {
070                try {
071                    if (context.getKernel().getService(dependency) == ServiceState.RUNNING) {
072                        satisfied = true;
073                        context.getKernel().removeServiceMonitor(serviceMonitor);
074                    }
075                } catch (ServiceNotFoundException ignored) {
076                    // service hasn't registered yet
077                }
078            }
079            return satisfied;
080        }
081    
082        /**
083         * {@inheritDoc}
084         */
085        public synchronized void destroy() {
086            if (context == null) {
087                // we are already destroyed
088                return;
089            }
090    
091            context.getKernel().removeServiceMonitor(serviceMonitor);
092            context = null;
093            satisfied = true;
094        }
095    
096        private class DependencyServiceMonitor extends NullServiceMonitor {
097            public void serviceStopped(ServiceEvent serviceEvent) {
098                synchronized (StoppedServiceCondition.this) {
099                    if (context != null) {
100                        // we aren't running anymore
101                        return;
102                    }
103    
104                    if (!satisfied) {
105                        return;
106                    }
107    
108                    if (isSatisfied()) {
109                        context.setSatisfied();
110                    }
111                }
112            }
113        }
114    }