001 /*
002 *
003 * Licensed to the Apache Software Foundation (ASF) under one
004 * or more contributor license agreements. See the NOTICE file
005 * distributed with this work for additional information
006 * regarding copyright ownership. The ASF licenses this file
007 * to you under the Apache License, Version 2.0 (the
008 * "License"); you may not use this file except in compliance
009 * with the License. You may obtain a copy of the License at
010 *
011 * http://www.apache.org/licenses/LICENSE-2.0
012 *
013 * Unless required by applicable law or agreed to in writing,
014 * software distributed under the License is distributed on an
015 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
016 * KIND, either express or implied. See the License for the
017 * specific language governing permissions and limitations
018 * under the License.
019 *
020 */
021 package org.apache.qpid.client.state;
022
023 import org.apache.qpid.client.util.BlockingWaiter;
024 import org.apache.qpid.client.failover.FailoverException;
025 import org.apache.qpid.AMQException;
026 import org.slf4j.LoggerFactory;
027 import org.slf4j.Logger;
028
029 import java.util.Set;
030
031 /**
032 * This is an implementation of the {@link BlockingWaiter} to provide error handing and a waiting mechanism for state
033 * changes.
034 *
035 * On construction the current state and a set of States to await for is provided.
036 *
037 * When await() is called the state at constuction is compared against the awaitStates. If the state at construction is
038 * a desired state then await() returns immediately.
039 *
040 * Otherwise it will block for the set timeout for a desired state to be achieved.
041 *
042 * The state changes are notified via the {@link #process} method.
043 *
044 * Any notified error is handled by the BlockingWaiter and thrown from the {@link #block} method.
045 *
046 */
047 public class StateWaiter extends BlockingWaiter<AMQState>
048 {
049 private static final Logger _logger = LoggerFactory.getLogger(StateWaiter.class);
050
051 Set<AMQState> _awaitStates;
052 private AMQState _startState;
053 private AMQStateManager _stateManager;
054
055 /**
056 *
057 * @param stateManager The StateManager
058 * @param currentState
059 * @param awaitStates
060 */
061 public StateWaiter(AMQStateManager stateManager, AMQState currentState, Set<AMQState> awaitStates)
062 {
063 _logger.info("New StateWaiter :" + currentState + ":" + awaitStates);
064 _stateManager = stateManager;
065 _awaitStates = awaitStates;
066 _startState = currentState;
067 }
068
069 /**
070 * When the state is changed this StateWaiter is notified to process the change.
071 *
072 * @param state The new state that has been achieved.
073 * @return
074 */
075 public boolean process(AMQState state)
076 {
077 return _awaitStates.contains(state);
078 }
079
080 /**
081 * Await for the requried State to be achieved within the default timeout.
082 * @return The achieved state that was requested.
083 * @throws AMQException The exception that prevented the required state from being achived.
084 */
085 public AMQState await() throws AMQException
086 {
087 return await(_stateManager.getWaitTimeout());
088 }
089
090 /**
091 * Await for the requried State to be achieved.
092 *
093 * <b>It is the responsibility of this class to remove the waiter from the StateManager
094 *
095 * @param timeout The time in milliseconds to wait for any of the states to be achived.
096 * @return The achieved state that was requested.
097 * @throws AMQException The exception that prevented the required state from being achived.
098 */
099 public AMQState await(long timeout) throws AMQException
100 {
101 try
102 {
103 if (process(_startState))
104 {
105 return _startState;
106 }
107
108 try
109 {
110 return (AMQState) block(timeout);
111 }
112 catch (FailoverException e)
113 {
114 _logger.error("Failover occured whilst waiting for states:" + _awaitStates);
115
116 e.printStackTrace();
117 return null;
118 }
119 }
120 finally
121 {
122 //Prevent any more errors being notified to this waiter.
123 close();
124
125 //Remove the waiter from the notifcation list in the statee manager
126 _stateManager.removeWaiter(this);
127 }
128 }
129 }
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