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    import java.io.Serializable;
020    
021    /**
022     * The state of services within the Kernel.  The state model is directly adapted from the J2EE Management Specification
023     * (JSR 77) with the removal of the FAILED state.
024     *
025     * @author Dain Sundstrom
026     * @version $Id$
027     * @since 2.0
028     */
029    public final class ServiceState implements Serializable {
030        private static final long serialVersionUID = -2629672602273580572L;
031    
032        /**
033         * This state indicates that the service is attempting to start but has not fully started yet.  Normally, a service
034         * in this state is waiting for a required service to enter the RUNNING state.
035         */
036        public static final ServiceState STARTING = new ServiceState((byte) 0, "STARTING");
037    
038        /**
039         * This state indicates that the service is in the normal operational state.
040         */
041        public static final ServiceState RUNNING = new ServiceState((byte) 1, "RUNNING");
042    
043        /**
044         * This state indicates that the service is attempting to stop but has not fully stopped yet.  Normally, a service
045         * in this state because another service is still usind this service.
046         */
047        public static final ServiceState STOPPING = new ServiceState((byte) 2, "STOPPING");
048    
049        /**
050         * This state indicates that the service is stopped and not operational.
051         */
052        public static final ServiceState STOPPED = new ServiceState((byte) 3, "STOPPED");
053    
054        /**
055         * A quick index for looking up service states.
056         */
057        private static final ServiceState[] serviceStateIndex = new ServiceState[]{STARTING, RUNNING, STOPPING, STOPPED};
058    
059        static {
060            for (int i = 0; i < serviceStateIndex.length; i++) {
061                ServiceState serviceState = serviceStateIndex[i];
062                if (serviceState.getIndex() != i) {
063                    throw new AssertionError(serviceState + " state index is " + serviceState.getIndex() +
064                        ", but is located at index " + i + " in the serviceStateIndex");
065                }
066            }
067        }
068    
069        /**
070         * Converts the state index into corresponding state name.
071         *
072         * @param state the state index
073         * @return the name of the state
074         * @throws IllegalArgumentException if the state index is not 0, 1, 2 or 3
075         */
076        public static ServiceState getServiceState(int state) throws IllegalArgumentException {
077            if (state < 0 || state >= serviceStateIndex.length) {
078                throw new IllegalArgumentException("Unknown state " + state);
079            }
080            return serviceStateIndex[state];
081        }
082    
083        /**
084         * Converts the state name in the corresponding state index.  This method performs a case insensitive comparison.
085         *
086         * @param state the state name
087         * @return the state index
088         * @throws IllegalArgumentException if the state index is not STARTING, RUNNING, STOPPING or FAILED
089         */
090        public static ServiceState parseServiceState(String state) {
091            if (state == null) throw new NullPointerException("state is null");
092            if (STARTING.toString().equalsIgnoreCase(state)) {
093                return STARTING;
094            } else if (RUNNING.toString().equalsIgnoreCase(state)) {
095                return RUNNING;
096            } else if (STOPPING.toString().equalsIgnoreCase(state)) {
097                return STOPPING;
098            } else if (STOPPED.toString().equalsIgnoreCase(state)) {
099                return STOPPED;
100            } else {
101                throw new IllegalArgumentException("Unknown state " + state);
102            }
103        }
104    
105        private final byte index;
106        private final transient String name;
107    
108        private ServiceState(byte index, String name) {
109            this.index = index;
110            this.name = name;
111        }
112    
113        /**
114         * Gets the unique index of this state.  This index can be be used to retrieve this state instance using the
115         * getServiceState(int) method.
116         *
117         * @return the unique index of this state
118         */
119        public int getIndex() {
120            return index;
121        }
122    
123        /**
124         * The unique name of this state.  This uppercase name can be used to retrieve this state instance using the
125         * parseServiceState(String).
126         *
127         * @return the unique name of this state
128         */
129        public String getName() {
130            return name;
131        }
132    
133        /**
134         * Returns the name of this state.
135         *
136         * @return the unique name of this state
137         */
138        public String toString() {
139            return name;
140        }
141    
142        private Object readResolve() {
143            return serviceStateIndex[index];
144        }
145    }