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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;
import javax.jms.IllegalStateException;
import javax.jms.JMSException;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* Captures the 'closed' state of an object, that is initially open, can be tested to see if it is closed, and provides
* a 'close' method to close it.
*
* <p/><table id="crc"><caption>CRC Card</caption>
* <tr><th> Responsibilities <th> Collaborations
* <tr><td> Mark an object as closed.
* <tr><td> Check if an object is closed.
* <tr><td> Raise a JMS exception if an object is closed.
* </table>
*
* @todo Might be better to make this an interface. This whole class doesn't really encapsulate a terribly neat
* piece of re-usable functionality. A simple interface defining a close method would suffice.
*
* @todo The convenience method {@link #checkNotClosed} is not that helpfull, what if the caller wants to do something
* other than throw an exception? It doesn't really represent a very usefull re-usable piece of code. Consider
* inlining it and dropping the method.
*/
public abstract class Closeable
{
/**
* We use an atomic boolean so that we do not have to synchronized access to this flag. Synchronizing access to this
* flag would mean have a synchronized block in every method.
*/
private final AtomicBoolean _closed = new AtomicBoolean(false);
/**
* Are we in the process of closing. We have this distinction so we can
* still signal we are in the process of closing so other objects can tell
* the difference and tidy up.
*/
private final AtomicBoolean _closing = new AtomicBoolean(false);
/**
* Checks if this is closed, and raises a JMSException if it is.
*
* @throws JMSException If this is closed.
*/
protected void checkNotClosed() throws JMSException
{
if (isClosed())
{
throw new IllegalStateException("Object " + toString() + " has been closed");
}
}
/**
* Checks if this is closed.
*
* @return <tt>true</tt> if this is closed, <tt>false</tt> otherwise.
*/
public boolean isClosed()
{
return _closed.get();
}
/**
* Checks if this is closis.
*
* @return <tt>true</tt> if we are closing, <tt>false</tt> otherwise.
*/
public boolean isClosing()
{
return _closing.get();
}
protected boolean setClosed()
{
return _closed.getAndSet(true);
}
protected void setClosing(boolean closing)
{
_closing.set(closing);
}
/**
* Closes this object.
*
* @throws JMSException If this cannot be closed for any reason.
*/
public abstract void close() throws JMSException;
}
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