org.springframework.aop.target.AbstractPoolingTargetSource.java Source code

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Here is the source code for org.springframework.aop.target.AbstractPoolingTargetSource.java

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/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed 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
 *
 *      https://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.springframework.aop.target;

import org.springframework.aop.support.DefaultIntroductionAdvisor;
import org.springframework.aop.support.DelegatingIntroductionInterceptor;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanInitializationException;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.lang.Nullable;

/**
 * Abstract base class for pooling {@link org.springframework.aop.TargetSource}
 * implementations which maintain a pool of target instances, acquiring and
 * releasing a target object from the pool for each method invocation.
 * This abstract base class is independent of concrete pooling technology;
 * see the subclass {@link CommonsPool2TargetSource} for a concrete example.
 *
 * <p>Subclasses must implement the {@link #getTarget} and
 * {@link #releaseTarget} methods based on their chosen object pool.
 * The {@link #newPrototypeInstance()} method inherited from
 * {@link AbstractPrototypeBasedTargetSource} can be used to create objects
 * in order to put them into the pool.
 *
 * <p>Subclasses must also implement some of the monitoring methods from the
 * {@link PoolingConfig} interface. The {@link #getPoolingConfigMixin()} method
 * makes these stats available on proxied objects through an IntroductionAdvisor.
 *
 * <p>This class implements the {@link org.springframework.beans.factory.DisposableBean}
 * interface in order to force subclasses to implement a {@link #destroy()}
 * method, closing down their object pool.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see #getTarget
 * @see #releaseTarget
 * @see #destroy
 */
@SuppressWarnings("serial")
public abstract class AbstractPoolingTargetSource extends AbstractPrototypeBasedTargetSource
        implements PoolingConfig, DisposableBean {

    /** The maximum size of the pool. */
    private int maxSize = -1;

    /**
     * Set the maximum size of the pool.
     * Default is -1, indicating no size limit.
     */
    public void setMaxSize(int maxSize) {
        this.maxSize = maxSize;
    }

    /**
     * Return the maximum size of the pool.
     */
    @Override
    public int getMaxSize() {
        return this.maxSize;
    }

    @Override
    public final void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        super.setBeanFactory(beanFactory);
        try {
            createPool();
        } catch (Throwable ex) {
            throw new BeanInitializationException("Could not create instance pool for TargetSource", ex);
        }
    }

    /**
     * Create the pool.
     * @throws Exception to avoid placing constraints on pooling APIs
     */
    protected abstract void createPool() throws Exception;

    /**
     * Acquire an object from the pool.
     * @return an object from the pool
     * @throws Exception we may need to deal with checked exceptions from pool
     * APIs, so we're forgiving with our exception signature
     */
    @Override
    @Nullable
    public abstract Object getTarget() throws Exception;

    /**
     * Return the given object to the pool.
     * @param target object that must have been acquired from the pool
     * via a call to {@code getTarget()}
     * @throws Exception to allow pooling APIs to throw exception
     * @see #getTarget
     */
    @Override
    public abstract void releaseTarget(Object target) throws Exception;

    /**
     * Return an IntroductionAdvisor that providing a mixin
     * exposing statistics about the pool maintained by this object.
     */
    public DefaultIntroductionAdvisor getPoolingConfigMixin() {
        DelegatingIntroductionInterceptor dii = new DelegatingIntroductionInterceptor(this);
        return new DefaultIntroductionAdvisor(dii, PoolingConfig.class);
    }

}