/*
 * 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.
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package org.apache.commons.pool;

A simple base implementation of KeyedObjectPool. Optional operations are implemented to either do nothing, return a value indicating it is unsupported or throw UnsupportedOperationException. 
Author:
Rodney Waldhoff, Sandy McArthur
Type parameters:
<K> – the type of keys in this pool
<V> – the type of objects held in this pool
Version:
$Revision: 1222396 $ $Date: 2011-12-22 14:02:25 -0500 (Thu, 22 Dec 2011) $
Since:
Pool 1.0/**
 * A simple base implementation of <code>KeyedObjectPool</code>.
 * Optional operations are implemented to either do nothing, return a value
 * indicating it is unsupported or throw {@link UnsupportedOperationException}.
 *
 * @param <K> the type of keys in this pool
 * @param <V> the type of objects held in this pool
 * 
 * @author Rodney Waldhoff
 * @author Sandy McArthur
 * @version $Revision: 1222396 $ $Date: 2011-12-22 14:02:25 -0500 (Thu, 22 Dec 2011) $
 * @since Pool 1.0
 */
public abstract class BaseKeyedObjectPool<K, V> implements KeyedObjectPool<K, V> {
    
    
{@inheritDoc}
/**
     * {@inheritDoc}
     */
    public abstract V borrowObject(K key) throws Exception;
    
    
{@inheritDoc}
/**
     * {@inheritDoc}
     */
    public abstract void returnObject(K key, V obj) throws Exception;
    
    
Invalidates an object from the pool.
By contract, obj must have been obtained using borrowObject using a key that is
equivalent to the one used to borrow the Object in the first place.
This method should be used when an object that has been borrowed
is determined (due to an exception or other problem) to be invalid.
Params:
key – the key used to obtain the object
obj – a borrowed instance to be returned.
Throws:
Exception – /**
     * <p>Invalidates an object from the pool.</p>
     * 
     * <p>By contract, <code>obj</code> <strong>must</strong> have been obtained
     * using {@link #borrowObject borrowObject} using a <code>key</code> that is
     * equivalent to the one used to borrow the <code>Object</code> in the first place.</p>
     *
     * <p>This method should be used when an object that has been borrowed
     * is determined (due to an exception or other problem) to be invalid.</p>
     *
     * @param key the key used to obtain the object
     * @param obj a {@link #borrowObject borrowed} instance to be returned.
     * @throws Exception 
     */
    public abstract void invalidateObject(K key, V obj) throws Exception;

    
Not supported in this base implementation. Always throws an UnsupportedOperationException, subclasses should override this behavior. 
Params:
key – ignored
Throws:
UnsupportedOperationException – /**
     * Not supported in this base implementation.
     * Always throws an {@link UnsupportedOperationException},
     * subclasses should override this behavior.
     * @param key ignored
     * @throws UnsupportedOperationException
     */
    public void addObject(K key) throws Exception, UnsupportedOperationException {
        throw new UnsupportedOperationException();
    }

    
Not supported in this base implementation.
Params:
key – ignored
Returns:
a negative value./**
     * Not supported in this base implementation.
     * @return a negative value.
     * @param key ignored
     */
    public int getNumIdle(K key) throws UnsupportedOperationException {
        return -1;
    }

    
Not supported in this base implementation.
Params:
key – ignored
Returns:
a negative value./**
     * Not supported in this base implementation.
     * @return a negative value.
     * @param key ignored
     */
    public int getNumActive(K key) throws UnsupportedOperationException {
        return -1;
    }

    
Not supported in this base implementation.
Returns:
a negative value./**
     * Not supported in this base implementation.
     * @return a negative value.
     */
    public int getNumIdle() throws UnsupportedOperationException {
        return -1;
    }

    
Not supported in this base implementation.
Returns:
a negative value./**
     * Not supported in this base implementation.
     * @return a negative value.
     */
    public int getNumActive() throws UnsupportedOperationException {
        return -1;
    }

    
Not supported in this base implementation.
Throws:
UnsupportedOperationException – /**
     * Not supported in this base implementation.
     * @throws UnsupportedOperationException
     */
    public void clear() throws Exception, UnsupportedOperationException {
        throw new UnsupportedOperationException();
    }

    
Not supported in this base implementation.
Params:
key – ignored
Throws:
UnsupportedOperationException – /**
     * Not supported in this base implementation.
     * @param key ignored
     * @throws UnsupportedOperationException
     */
    public void clear(K key) throws Exception, UnsupportedOperationException {
        throw new UnsupportedOperationException();
    }

    
Close this pool.
This affects the behavior of isClosed and assertOpen.
/**
     * Close this pool.
     * This affects the behavior of <code>isClosed</code> and <code>assertOpen</code>.
     */
    public void close() throws Exception {
        closed = true;
    }

    
Not supported in this base implementation. Always throws an UnsupportedOperationException, subclasses should override this behavior. 
Params:
factory – the new KeyedPoolableObjectFactory
Deprecated:
to be removed in pool 2.0/**
     * Not supported in this base implementation.
     * Always throws an {@link UnsupportedOperationException},
     * subclasses should override this behavior.
     * @param factory the new KeyedPoolableObjectFactory
     * @deprecated to be removed in pool 2.0
     */
    @Deprecated
    public void setFactory(KeyedPoolableObjectFactory<K, V> factory) throws IllegalStateException, UnsupportedOperationException {
        throw new UnsupportedOperationException();
    }

    
Has this pool instance been closed.
Returns:
true when this pool has been closed.
Since:
Pool 1.4/**
     * Has this pool instance been closed.
     * @return <code>true</code> when this pool has been closed.
     * @since Pool 1.4
     */
    protected final boolean isClosed() {
        return closed;
    }

    
Throws an IllegalStateException when this pool has been closed.
Throws:
IllegalStateException – when this pool has been closed.
See Also:
isClosed()
Since:
Pool 1.4/**
     * Throws an <code>IllegalStateException</code> when this pool has been closed.
     * @throws IllegalStateException when this pool has been closed.
     * @see #isClosed()
     * @since Pool 1.4
     */
    protected final void assertOpen() throws IllegalStateException {
        if(isClosed()) {
            throw new IllegalStateException("Pool not open");
        }
    }

    
Whether or not the pool is close /** Whether or not the pool is close */
    private volatile boolean closed = false;
}