abstractadvisorautoproxycreator.java

spring的源代码

/*
 * Copyright 2002-2005 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
 * 
 *      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.springframework.aop.framework.autoproxy;

import java.util.List;

import org.springframework.aop.TargetSource;
import org.springframework.aop.support.AopUtils;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.core.ControlFlow;
import org.springframework.core.ControlFlowFactory;

/**
 * Abstract BeanPostProcessor implementation that creates AOP proxies. 
 * This class is completely generic; it contains no special code to handle
 * any particular aspects, such as pooling aspects.
 *
 * <p>Subclasses must implement the abstract <code>findCandidateAdvisors()</code>
 * method to return a list of Advisors applying to any object. Subclasses can
 * also override the inherited <code>shouldSkip</code> method to exclude certain
 * objects from auto-proxying, but they must be careful to invoke the base
 * <code>shouldSkip</code> method, which tries to avoid circular reference
 * problems and infinite loops.
 *
 * <p>Advisors or advices requiring ordering should implement the Ordered interface.
 * This class sorts advisors by Ordered order value. Advisors that don't implement
 * the Ordered interface will be considered to be unordered, and will appear
 * at the end of the advisor chain in undefined order.
 *
 * @author Rod Johnson
 * @see #findCandidateAdvisors
 * @see org.springframework.aop.support.AopUtils
 */
public abstract class AbstractAdvisorAutoProxyCreator extends AbstractAutoProxyCreator {

	/**
	 * We override this method to ensure that all candidate advisors are materialized
	 * under a stack trace including this bean. Otherwise, the dependencies won't
	 * be apparent to the circular-reference prevention strategy in AbstractBeanFactory.
	 */
	public void setBeanFactory(BeanFactory beanFactory) {
		super.setBeanFactory(beanFactory);
		findCandidateAdvisors();
	}


	protected Object[] getAdvicesAndAdvisorsForBean(Class beanClass, String name, TargetSource targetSource) {
		List advisors = findEligibleAdvisors(beanClass);
		if (advisors.isEmpty()) {
			return DO_NOT_PROXY;
		}
		advisors = sortAdvisors(advisors);
		return advisors.toArray();
	}

	/**
	 * Find all eligible advices for auto-proxying this class.
	 * @return the empty list, not null, if there are no pointcuts or interceptors
	 * @see #findCandidateAdvisors
	 */
	protected List findEligibleAdvisors(Class clazz) {
		return AopUtils.findAdvisorsThatCanApply(findCandidateAdvisors(), clazz);
	}

	/**
	 * Sort advisors based on ordering.
	 * @see org.springframework.core.Ordered
	 * @see org.springframework.core.OrderComparator
	 */
	protected List sortAdvisors(List advisors) {
		return AopUtils.sortAdvisorsByOrder(advisors);
	}

	/**
	 * We override this to ensure that we don't get into circular reference hell
	 * when our own infrastructure (such as this class) depends on advisors that depend
	 * on beans... We use a ControlFlow object to check that we didn't arrived at this
	 * call via this classes findCandidateAdvisors() method.
	 * @see org.springframework.core.ControlFlow
	 */
	protected boolean shouldSkip(Class beanClass, String name) {
		// TODO consider pulling this test into AbstractBeanFactory.applyPostProcessors(),
		// to protect all PostProcessors.
		ControlFlow cflow = ControlFlowFactory.createControlFlow();
		return cflow.under(getClass(), "findCandidateAdvisors");
	}


	/**
	 * Find all candidate advisors to use in auto-proxying.
	 * @return list of Advisors
	 */
	protected abstract List findCandidateAdvisors();

}