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/*
*
* 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.qpid.client.state;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.qpid.AMQException;
import org.apache.qpid.client.failover.FailoverException;
import org.apache.qpid.client.util.BlockingWaiter;
import java.util.Set;
/**
* This is an implementation of the {@link BlockingWaiter} to provide error handing and a waiting mechanism for state
* changes.
*
* On construction the current state and a set of States to await for is provided.
*
* When await() is called the state at construction is compared against the awaitStates. If the state at construction is
* a desired state then await() returns immediately.
*
* Otherwise it will block for the set timeout for a desired state to be achieved.
*
* The state changes are notified via the {@link #process} method.
*
* Any notified error is handled by the BlockingWaiter and thrown from the {@link #block} method.
*
*/
public class StateWaiter extends BlockingWaiter<AMQState>
{
private static final Logger _logger = LoggerFactory.getLogger(StateWaiter.class);
private final Set<AMQState> _awaitStates;
private final AMQState _startState;
private final AMQStateManager _stateManager;
/**
*
* @param stateManager The StateManager
* @param currentState
* @param awaitStates
*/
public StateWaiter(AMQStateManager stateManager, AMQState currentState, Set<AMQState> awaitStates)
{
if(_logger.isDebugEnabled())
{
_logger.debug("New StateWaiter :" + currentState + ":" + awaitStates);
}
_stateManager = stateManager;
_awaitStates = awaitStates;
_startState = currentState;
}
/**
* When the state is changed this StateWaiter is notified to process the change.
*
* @param state The new state that has been achieved.
* @return
*/
public boolean process(AMQState state)
{
return _awaitStates.contains(state);
}
/**
* Await for the required State to be achieved within the default timeout.
* @return The achieved state that was requested.
* @throws AMQException The exception that prevented the required state from being achieved.
*/
public AMQState await() throws AMQException
{
return await(_stateManager.getWaitTimeout());
}
/**
* Await for the required State to be achieved.
*
* <b>It is the responsibility of this class to remove the waiter from the StateManager
*
* @param timeout The time in milliseconds to wait for any of the states to be achieved.
* @return The achieved state that was requested.
* @throws AMQException The exception that prevented the required state from being achieved.
*/
public AMQState await(long timeout) throws AMQException
{
try
{
if (process(_startState))
{
return _startState;
}
try
{
return (AMQState) block(timeout);
}
catch (FailoverException e)
{
_logger.error("Failover occured whilst waiting for states:" + _awaitStates);
return null;
}
}
finally
{
//Prevent any more errors being notified to this waiter.
close();
//Remove the waiter from the notifcation list in the statee manager
_stateManager.removeWaiter(this);
}
}
}
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