    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 */
    017package org.apache.commons.pool2;
    018
    019/**
    020 * A simple base implementation of {@link ObjectPool}.
    021 * Optional operations are implemented to either do nothing, return a value
    022 * indicating it is unsupported or throw {@link UnsupportedOperationException}.
    023 * <p>
    024 * This class is intended to be thread-safe.
    025 *
    026 * @param <T> Type of element pooled in this pool.
    027 *
    028 * @since 2.0
    029 */
    030public abstract class BaseObjectPool<T> extends BaseObject implements ObjectPool<T> {
    031
    032    @Override
    033    public abstract T borrowObject() throws Exception;
    034
    035    @Override
    036    public abstract void returnObject(T obj) throws Exception;
    037
    038    @Override
    039    public abstract void invalidateObject(T obj) throws Exception;
    040
    041    /**
    042     * Not supported in this base implementation.
    043     *
    044     * @return a negative value.
    045     */
    046    @Override
    047    public int getNumIdle() {
    048        return -1;
    049    }
    050
    051    /**
    052     * Not supported in this base implementation.
    053     *
    054     * @return a negative value.
    055     */
    056    @Override
    057    public int getNumActive() {
    058        return -1;
    059    }
    060
    061    /**
    062     * Not supported in this base implementation.
    063     *
    064     * @throws UnsupportedOperationException if the pool does not implement this
    065     *          method
    066     */
    067    @Override
    068    public void clear() throws Exception, UnsupportedOperationException {
    069        throw new UnsupportedOperationException();
    070    }
    071
    072    /**
    073     * Not supported in this base implementation. Subclasses should override
    074     * this behavior.
    075     *
    076     * @throws UnsupportedOperationException if the pool does not implement this
    077     *          method
    078     */
    079    @Override
    080    public void addObject() throws Exception, UnsupportedOperationException {
    081        throw new UnsupportedOperationException();
    082    }
    083
    084    /**
    085     * {@inheritDoc}
    086     * <p>
    087     * This affects the behavior of <code>isClosed</code> and
    088     * <code>assertOpen</code>.
    089     * </p>
    090     */
    091    @Override
    092    public void close() {
    093        closed = true;
    094    }
    095
    096    /**
    097     * Has this pool instance been closed.
    098     *
    099     * @return <code>true</code> when this pool has been closed.
    100     */
    101    public final boolean isClosed() {
    102        return closed;
    103    }
    104
    105    /**
    106     * Throws an <code>IllegalStateException</code> when this pool has been
    107     * closed.
    108     *
    109     * @throws IllegalStateException when this pool has been closed.
    110     *
    111     * @see #isClosed()
    112     */
    113    protected final void assertOpen() throws IllegalStateException {
    114        if (isClosed()) {
    115            throw new IllegalStateException("Pool not open");
    116        }
    117    }
    118
    119    private volatile boolean closed = false;
    120
    121    @Override
    122    protected void toStringAppendFields(final StringBuilder builder) {
    123        builder.append("closed=");
    124        builder.append(closed);
    125    }
    126}