abstractautoproxycreator.java

spring的源代码

/*
 * Copyright 2002-2004 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.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

import org.aopalliance.intercept.MethodInterceptor;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.aop.Advisor;
import org.springframework.aop.TargetSource;
import org.springframework.aop.framework.ProxyConfig;
import org.springframework.aop.framework.ProxyFactory;
import org.springframework.aop.framework.adapter.GlobalAdvisorAdapterRegistry;
import org.springframework.aop.support.AopUtils;
import org.springframework.aop.target.SingletonTargetSource;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.core.Ordered;

/**
 * BeanPostProcessor implementation that wraps a group of beans with AOP proxies
 * that delegate to the given interceptors before invoking the bean itself.
 * 
 * <p>This class distinguishes between "common" interceptors: shared for all proxies it
 * creators, and "specific" interceptors: unique per bean instance. There need not
 * be any common interceptors. If there are, they are set using the interceptorNames
 * property. As with ProxyFactoryBean, interceptors names in the current factory
 * are used rather than bean references to allow correct handling of prototype
 * advisors and interceptors: for example, to support stateful mixins. 
 * Any advice type is supported for "interceptorNames" entries. 
 *
 * <p>Such autoproxying is particularly useful if there's a large number of beans that need
 * to be wrapped with similar proxies, i.e. delegating to the same interceptors.
 * Instead of x repetitive proxy definitions for x target beans, you can register
 * one single such post processor with the bean factory to achieve the same effect.
 *
 * <p>Subclasses can apply any strategy to decide if a bean is to be proxied,
 * e.g. by type, by name, by definition details, etc. They can also return
 * additional interceptors that should just be applied to the specific bean
 * instance. The default concrete implementation is BeanNameAutoProxyCreator,
 * identifying the beans to be proxied via a list of bean names.
 * 
 * <p>Any number of TargetSourceCreator implementations can be used with
 * any subclass, to create a custom target source--for example, to pool prototype
 * objects. Autoproxying will occur even if there is no advice if a TargetSourceCreator
 * specifies a custom TargetSource.
 * If there are no TargetSourceCreators set, or if none matches, a SingletonTargetSource
 * will be used by default to wrap the bean to be autoproxied.
 *
 * @author Juergen Hoeller
 * @author Rod Johnson
 * @since October 13, 2003
 * @see #setInterceptorNames
 * @see BeanNameAutoProxyCreator
 * @version $Id: AbstractAutoProxyCreator.java,v 1.8 2004/04/01 15:36:01 jhoeller Exp $
 */
public abstract class AbstractAutoProxyCreator extends ProxyConfig
		implements BeanPostProcessor, BeanFactoryAware, Ordered {

	/**
	 * Convenience constant for subclasses: Return value for "do not proxy".
	 * @see #getInterceptorsAndAdvisorsForBean
	 */
	protected final Object[] DO_NOT_PROXY = null;

	/**
	 * Convenience constant for subclasses: Return value for
	 * "proxy without additional interceptors, just the common ones".
	 * @see #getInterceptorsAndAdvisorsForBean
	 */
	protected final Object[] PROXY_WITHOUT_ADDITIONAL_INTERCEPTORS = new Object[0];

	protected final Log logger = LogFactory.getLog(getClass());

	/**
	 * Default value is same as non-ordered
	 */
	private int order = Integer.MAX_VALUE; 

	/**
	 * Names of common interceptors. We must use bean name rather than object references
	 * to handle prototype advisors/interceptors.
	 * Default is the empty array: no common interceptors.
	 */
	private String[] interceptorNames = new String[0];

	private boolean applyCommonInterceptorsFirst = true;
	
	private List customTargetSourceCreators = Collections.EMPTY_LIST;
	
	private BeanFactory owningBeanFactory;
	

	/**
	 * Set the ordering which will apply to this class's implementation
	 * of Ordered, used when applying multiple BeanPostProcessors.
	 * Default value is Integer.MAX_VALUE, meaning that it's non-ordered.
	 * @param order ordering value
	 */
	public final void setOrder(int order) {
	  this.order = order;
	}

	public final int getOrder() {
	  return order;
	}
	
	/**
	 * Set custom TargetSourceCreators to be applied in this order.
	 * If the list is empty, or they all return null, a SingletonTargetSource
	 * will be created.
	 * <p>TargetSourceCreators can only be invoked if this post processor is used
	 * in a BeanFactory, and its BeanFactoryAware callback is used.
	 * @param targetSourceCreators list of TargetSourceCreator.
	 * Ordering is significant: The TargetSource returned from the first matching
	 * TargetSourceCreator (that is, the first that returns non-null) will be used.
	 */
	public void setCustomTargetSourceCreators(List targetSourceCreators) {
		this.customTargetSourceCreators = targetSourceCreators;
	}

	/**
	 * Set the common interceptors. These must be bean names
	 * in the current factory. They can be of any advice or#
	 * advisor type Spring supports. If this property isn't
	 * set, there will be zero common interceptors. This is
	 * perfectly valid, if "specific" interceptors such as
	 * matching Advisors are all we want.
	 */
	public void setInterceptorNames(String[] interceptorNames) {
		this.interceptorNames = interceptorNames;
	}

	/**
	 * Set whether the common interceptors should be applied before
	 * bean-specific ones. Default is true; else, bean-specific
	 * interceptors will get applied first.
	 */
	public void setApplyCommonInterceptorsFirst(boolean applyCommonInterceptorsFirst) {
		this.applyCommonInterceptorsFirst = applyCommonInterceptorsFirst;
	}
	
	public void setBeanFactory(BeanFactory beanFactory) {
		this.owningBeanFactory = beanFactory;
	}
	
	/**
	 * Return the owning BeanFactory
	 * May be null, as this object doesn't need to belong to a bean factory.
	 */
	protected BeanFactory getBeanFactory() {
		return this.owningBeanFactory;
	}


	public Object postProcessBeforeInitialization(Object bean, String name) {
		return bean;
	}

	/**
	 * Create a proxy with the configured interceptors if the bean is
	 * identified as one to proxy by the subclass.
	 * @see #getInterceptorsAndAdvisorsForBean
	 */
	public Object postProcessAfterInitialization(Object bean, String name) throws BeansException {
		// Check for special cases. We don't want to try to autoproxy a part of the autoproxying
		// infrastructure, lest we get a stack overflow.
		if (isInfrastructureClass(bean, name) || shouldSkip(bean, name)) {
			logger.debug("Did not attempt to autoproxy infrastructure class [" + bean.getClass().getName() + "]");
			return bean;
		}
		
		TargetSource targetSource = getTargetSource(bean, name);
		
		Object[] specificInterceptors = getInterceptorsAndAdvisorsForBean(bean, name);
		
		// proxy if we have advice or if a TargetSourceCreator wants to do some
		// fancy stuff such as pooling
		if (specificInterceptors != DO_NOT_PROXY || !(targetSource instanceof SingletonTargetSource)) {

			// handle prototypes correctly
			Advisor[] commonInterceptors = resolveInterceptorNames();

			List allInterceptors = new ArrayList();
			if (specificInterceptors != null) {
				allInterceptors.addAll(Arrays.asList(specificInterceptors));
				if (commonInterceptors != null) {
					if (this.applyCommonInterceptorsFirst) {
						allInterceptors.addAll(0, Arrays.asList(commonInterceptors));
					}
					else {
						allInterceptors.addAll(Arrays.asList(commonInterceptors));
					}
				}
			}
			if (logger.isInfoEnabled()) {
				int nrOfCommonInterceptors = commonInterceptors != null ? commonInterceptors.length : 0;
				int nrOfSpecificInterceptors = specificInterceptors != null ? specificInterceptors.length : 0;
				logger.info("Creating implicit proxy for bean '" +  name + "' with " + nrOfCommonInterceptors +
										" common interceptors and " + nrOfSpecificInterceptors + " specific interceptors");
			}

			ProxyFactory proxyFactory = new ProxyFactory();
			// copy our properties (proxyTargetClass) inherited from ProxyConfig
			proxyFactory.copyFrom(this);
			
			if (!getProxyTargetClass()) {
				// Must allow for introductions; can't just set interfaces to
				// the target's interfaces only.
				Class[] targetsInterfaces = AopUtils.getAllInterfaces(bean);
				for (int i = 0; i < targetsInterfaces.length; i++) {
					proxyFactory.addInterface(targetsInterfaces[i]);
				}
			}
			
			for (Iterator it = allInterceptors.iterator(); it.hasNext();) {
				Advisor advisor = GlobalAdvisorAdapterRegistry.getInstance().wrap(it.next());
				proxyFactory.addAdvisor(advisor);
			}
			proxyFactory.setTargetSource(getTargetSource(bean, name));
			
			return proxyFactory.getProxy();
		}
		else {
			return bean;
		}
	}

	private Advisor[] resolveInterceptorNames() {
		Advisor[] advisors = new Advisor[this.interceptorNames.length];
		for (int i = 0; i < this.interceptorNames.length; i++) {
			Object next = this.owningBeanFactory.getBean(this.interceptorNames[i]);
			advisors[i] = GlobalAdvisorAdapterRegistry.getInstance().wrap(next);
		}
		return advisors;
	}

	protected boolean isInfrastructureClass(Object bean, String name) {
		return Advisor.class.isAssignableFrom(bean.getClass()) ||
				MethodInterceptor.class.isAssignableFrom(bean.getClass()) ||
				AbstractAutoProxyCreator.class.isAssignableFrom(bean.getClass());
	}
	
	/**
	 * Subclasses should override this method to return true if this
	 * bean should not be considered for autoproxying by this post processor. 
	 * Sometimes we need to be able to avoid this happening if it will lead to
	 * a circular reference. This implementation returns true.
	 */
	protected boolean shouldSkip(Object bean, String name) {
		return false;
	}

	/**
	 * Create a target source to source instances.
	 * Uses any TargetSourceCreators if set.
	 * @param bean bean to intercept
	 * @param beanName name of the bean
	 * @return an invoker interceptor wrapping this bean.
	 * This implementation returns a straight reflection InvokerInterceptor
	 */
	private TargetSource getTargetSource(Object bean, String beanName) {
		// we can't create fancy target sources for singletons
		if (this.owningBeanFactory != null && !this.owningBeanFactory.isSingleton(beanName)) {
			logger.info("Checking for custom TargetSource for bean with name '" + beanName + "'");
			for (int i = 0; i < this.customTargetSourceCreators.size(); i++) {
				TargetSourceCreator tsc = (TargetSourceCreator) this.customTargetSourceCreators.get(i);
				TargetSource ts = tsc.getTargetSource(bean, beanName, this.owningBeanFactory);
				if (ts != null) {
					// found a match
					logger.info("TargetSourceCreator [" + tsc + " found custom TargetSource for bean with name '" + beanName + "'");
					return ts;
				}
			}
		}
		// default is a simple, default target source
		return new SingletonTargetSource(bean);
	}

	/**
	 * Return whether the given bean is to be proxied,
	 * and what additional interceptors and pointcuts to apply.
	 * @param bean the new bean instance
	 * @param beanName the beanName of the bean
	 * @return an array of additional interceptors for the particular bean;
	 * or an empty array if no additional interceptors but just the common ones;
	 * or null if no proxy at all, not even with the common interceptors.
	 * See constants DO_NOT_PROXY and PROXY_WITHOUT_ADDITIONAL_INTERCEPTORS.
	 * @throws org.springframework.beans.BeansException in case of errors
	 * @see #postProcessAfterInitialization
	 * @see #DO_NOT_PROXY
	 * @see #PROXY_WITHOUT_ADDITIONAL_INTERCEPTORS
	 */
	protected abstract Object[] getInterceptorsAndAdvisorsForBean(Object bean, String beanName)
	    throws BeansException;

}