001/*
002 * Copyright 2002-2018 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.aop.target;
018
019import org.springframework.aop.support.DefaultIntroductionAdvisor;
020import org.springframework.aop.support.DelegatingIntroductionInterceptor;
021import org.springframework.beans.BeansException;
022import org.springframework.beans.factory.BeanFactory;
023import org.springframework.beans.factory.BeanInitializationException;
024import org.springframework.beans.factory.DisposableBean;
025import org.springframework.lang.Nullable;
026
027/**
028 * Abstract base class for pooling {@link org.springframework.aop.TargetSource}
029 * implementations which maintain a pool of target instances, acquiring and
030 * releasing a target object from the pool for each method invocation.
031 * This abstract base class is independent of concrete pooling technology;
032 * see the subclass {@link CommonsPool2TargetSource} for a concrete example.
033 *
034 * <p>Subclasses must implement the {@link #getTarget} and
035 * {@link #releaseTarget} methods based on their chosen object pool.
036 * The {@link #newPrototypeInstance()} method inherited from
037 * {@link AbstractPrototypeBasedTargetSource} can be used to create objects
038 * in order to put them into the pool.
039 *
040 * <p>Subclasses must also implement some of the monitoring methods from the
041 * {@link PoolingConfig} interface. The {@link #getPoolingConfigMixin()} method
042 * makes these stats available on proxied objects through an IntroductionAdvisor.
043 *
044 * <p>This class implements the {@link org.springframework.beans.factory.DisposableBean}
045 * interface in order to force subclasses to implement a {@link #destroy()}
046 * method, closing down their object pool.
047 *
048 * @author Rod Johnson
049 * @author Juergen Hoeller
050 * @see #getTarget
051 * @see #releaseTarget
052 * @see #destroy
053 */
054@SuppressWarnings("serial")
055public abstract class AbstractPoolingTargetSource extends AbstractPrototypeBasedTargetSource
056                implements PoolingConfig, DisposableBean {
057
058        /** The maximum size of the pool. */
059        private int maxSize = -1;
060
061
062        /**
063         * Set the maximum size of the pool.
064         * Default is -1, indicating no size limit.
065         */
066        public void setMaxSize(int maxSize) {
067                this.maxSize = maxSize;
068        }
069
070        /**
071         * Return the maximum size of the pool.
072         */
073        @Override
074        public int getMaxSize() {
075                return this.maxSize;
076        }
077
078
079        @Override
080        public final void setBeanFactory(BeanFactory beanFactory) throws BeansException {
081                super.setBeanFactory(beanFactory);
082                try {
083                        createPool();
084                }
085                catch (Throwable ex) {
086                        throw new BeanInitializationException("Could not create instance pool for TargetSource", ex);
087                }
088        }
089
090
091        /**
092         * Create the pool.
093         * @throws Exception to avoid placing constraints on pooling APIs
094         */
095        protected abstract void createPool() throws Exception;
096
097        /**
098         * Acquire an object from the pool.
099         * @return an object from the pool
100         * @throws Exception we may need to deal with checked exceptions from pool
101         * APIs, so we're forgiving with our exception signature
102         */
103        @Override
104        @Nullable
105        public abstract Object getTarget() throws Exception;
106
107        /**
108         * Return the given object to the pool.
109         * @param target object that must have been acquired from the pool
110         * via a call to {@code getTarget()}
111         * @throws Exception to allow pooling APIs to throw exception
112         * @see #getTarget
113         */
114        @Override
115        public abstract void releaseTarget(Object target) throws Exception;
116
117
118        /**
119         * Return an IntroductionAdvisor that providing a mixin
120         * exposing statistics about the pool maintained by this object.
121         */
122        public DefaultIntroductionAdvisor getPoolingConfigMixin() {
123                DelegatingIntroductionInterceptor dii = new DelegatingIntroductionInterceptor(this);
124                return new DefaultIntroductionAdvisor(dii, PoolingConfig.class);
125        }
126
127}