Spring Framework example source code file (ProxyFactoryBean.java)

This example Spring Framework source code file (ProxyFactoryBean.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Spring Framework tags/keywords

advice, advisor, advisor, aopconfigexception, beanfactory, class, io, object, object, prototypeplaceholderadvisor, proxycreatorsupport, string, string, targetsource, targetsource, util

The Spring Framework ProxyFactoryBean.java source code

/*
 * Copyright 2002-2008 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;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.aopalliance.aop.Advice;
import org.aopalliance.intercept.Interceptor;
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.adapter.AdvisorAdapterRegistry;
import org.springframework.aop.framework.adapter.GlobalAdvisorAdapterRegistry;
import org.springframework.aop.framework.adapter.UnknownAdviceTypeException;
import org.springframework.aop.target.SingletonTargetSource;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanClassLoaderAware;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.BeanFactoryUtils;
import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.FactoryBeanNotInitializedException;
import org.springframework.beans.factory.ListableBeanFactory;
import org.springframework.core.OrderComparator;
import org.springframework.util.ClassUtils;
import org.springframework.util.ObjectUtils;

/**
 * {@link org.springframework.beans.factory.FactoryBean} implementation that builds an
 * AOP proxy based on beans in Spring {@link org.springframework.beans.factory.BeanFactory}.
 *
 * <p>{@link org.aopalliance.intercept.MethodInterceptor MethodInterceptors} and
 * {@link org.springframework.aop.Advisor Advisors} are identified by a list of bean
 * names in the current bean factory, specified through the "interceptorNames" property.
 * The last entry in the list can be the name of a target bean or a
 * {@link org.springframework.aop.TargetSource}; however, it is normally preferable
 * to use the "targetName"/"target"/"targetSource" properties instead.
 *
 * <p>Global interceptors and advisors can be added at the factory level. The specified
 * ones are expanded in an interceptor list where an "xxx*" entry is included in the
 * list, matching the given prefix with the bean names (e.g. "global*" would match
 * both "globalBean1" and "globalBean2", "*" all defined interceptors). The matching
 * interceptors get applied according to their returned order value, if they implement
 * the {@link org.springframework.core.Ordered} interface.
 *
 * <p>Creates a JDK proxy when proxy interfaces are given, and a CGLIB proxy for the
 * actual target class if not. Note that the latter will only work if the target class
 * does not have final methods, as a dynamic subclass will be created at runtime.
 *
 * <p>It's possible to cast a proxy obtained from this factory to {@link Advised},
 * or to obtain the ProxyFactoryBean reference and programmatically manipulate it.
 * This won't work for existing prototype references, which are independent. However,
 * it will work for prototypes subsequently obtained from the factory. Changes to
 * interception will work immediately on singletons (including existing references).
 * However, to change interfaces or target it's necessary to obtain a new instance
 * from the factory. This means that singleton instances obtained from the factory
 * do not have the same object identity. However, they do have the same interceptors
 * and target, and changing any reference will change all objects.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see #setInterceptorNames
 * @see #setProxyInterfaces
 * @see org.aopalliance.intercept.MethodInterceptor
 * @see org.springframework.aop.Advisor
 * @see Advised
 */
public class ProxyFactoryBean extends ProxyCreatorSupport
		implements FactoryBean, BeanClassLoaderAware, BeanFactoryAware {

	/**
	 * This suffix in a value in an interceptor list indicates to expand globals.
	 */
	public static final String GLOBAL_SUFFIX = "*";


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

	private String[] interceptorNames;
	
	private String targetName;

	private boolean autodetectInterfaces = true;

	private boolean singleton = true;

	private AdvisorAdapterRegistry advisorAdapterRegistry = GlobalAdvisorAdapterRegistry.getInstance();

	/**
	 * Indicates whether the proxy should be frozen before creation.
	 */
	private boolean freezeProxy = false;

	private transient ClassLoader beanClassLoader = ClassUtils.getDefaultClassLoader();

	/**
	 * Owning bean factory, which cannot be changed after this
	 * object is initialized.
	 */
	private transient BeanFactory beanFactory;

	/** Whether the advisor chain has already been initialized */
	private boolean advisorChainInitialized = false;

	/** If this is a singleton, the cached singleton proxy instance */
	private Object singletonInstance;


	/**
	 * Set the names of the interfaces we're proxying. If no interface
	 * is given, a CGLIB for the actual class will be created.
	 * <p>This is essentially equivalent to the "setInterfaces" method,
	 * but mirrors TransactionProxyFactoryBean's "setProxyInterfaces".
	 * @see #setInterfaces
	 * @see AbstractSingletonProxyFactoryBean#setProxyInterfaces
	 */
	public void setProxyInterfaces(Class[] proxyInterfaces) throws ClassNotFoundException {
		setInterfaces(proxyInterfaces);
	}

	/**
	 * Set the list of Advice/Advisor bean names. This must always be set
	 * to use this factory bean in a bean factory.
	 * <p>The referenced beans should be of type Interceptor, Advisor or Advice
	 * The last entry in the list can be the name of any bean in the factory.
	 * If it's neither an Advice nor an Advisor, a new SingletonTargetSource
	 * is added to wrap it. Such a target bean cannot be used if the "target"
	 * or "targetSource" or "targetName" property is set, in which case the
	 * "interceptorNames" array must contain only Advice/Advisor bean names.
	 * <p>NOTE: Specifying a target bean as final name in the "interceptorNames"
	 * list is deprecated and will be removed in a future Spring version.</b>
	 * Use the {@link #setTargetName "targetName"} property instead.
	 * @see org.aopalliance.intercept.MethodInterceptor
	 * @see org.springframework.aop.Advisor
	 * @see org.aopalliance.aop.Advice
	 * @see org.springframework.aop.target.SingletonTargetSource
	 */
	public void setInterceptorNames(String[] interceptorNames) {
		this.interceptorNames = interceptorNames;
	}

	/**
	 * Set the name of the target bean. This is an alternative to specifying
	 * the target name at the end of the "interceptorNames" array.
	 * <p>You can also specify a target object or a TargetSource object
	 * directly, via the "target"/"targetSource" property, respectively.
	 * @see #setInterceptorNames(String[])
	 * @see #setTarget(Object)
	 * @see #setTargetSource(org.springframework.aop.TargetSource)
	 */
	public void setTargetName(String targetName) {
		this.targetName = targetName;
	}

	/**
	 * Set whether to autodetect proxy interfaces if none specified.
	 * <p>Default is "true". Turn this flag off to create a CGLIB
	 * proxy for the full target class if no interfaces specified.
	 * @see #setProxyTargetClass
	 */
	public void setAutodetectInterfaces(boolean autodetectInterfaces) {
		this.autodetectInterfaces = autodetectInterfaces;
	}

	/**
	 * Set the value of the singleton property. Governs whether this factory
	 * should always return the same proxy instance (which implies the same target)
	 * or whether it should return a new prototype instance, which implies that
	 * the target and interceptors may be new instances also, if they are obtained
	 * from prototype bean definitions. This allows for fine control of
	 * independence/uniqueness in the object graph.
	 */
	public void setSingleton(boolean singleton) {
		this.singleton = singleton;
	}

	/**
	 * Specify the AdvisorAdapterRegistry to use.
	 * Default is the global AdvisorAdapterRegistry.
	 * @see org.springframework.aop.framework.adapter.GlobalAdvisorAdapterRegistry
	 */
	public void setAdvisorAdapterRegistry(AdvisorAdapterRegistry advisorAdapterRegistry) {
		this.advisorAdapterRegistry = advisorAdapterRegistry;
	}

	public void setFrozen(boolean frozen) {
		this.freezeProxy = frozen;
	}

	public void setBeanClassLoader(ClassLoader classLoader) {
		this.beanClassLoader = classLoader;
	}

	public void setBeanFactory(BeanFactory beanFactory) {
		this.beanFactory = beanFactory;
		checkInterceptorNames();
	}


	/**
	 * Return a proxy. Invoked when clients obtain beans from this factory bean.
	 * Create an instance of the AOP proxy to be returned by this factory.
	 * The instance will be cached for a singleton, and create on each call to
	 * <code>getObject() for a proxy.
	 * @return a fresh AOP proxy reflecting the current state of this factory
	 */
	public Object getObject() throws BeansException {
		initializeAdvisorChain();
		if (isSingleton()) {
			return getSingletonInstance();
		}
		else {
			if (this.targetName == null) {
				logger.warn("Using non-singleton proxies with singleton targets is often undesirable. " +
						"Enable prototype proxies by setting the 'targetName' property.");
			}
			return newPrototypeInstance();
		}
	}

	/**
	 * Return the type of the proxy. Will check the singleton instance if
	 * already created, else fall back to the proxy interface (in case of just
	 * a single one), the target bean type, or the TargetSource's target class.
	 * @see org.springframework.aop.TargetSource#getTargetClass
	 */
	public Class getObjectType() {
		synchronized (this) {
			if (this.singletonInstance != null) {
				return this.singletonInstance.getClass();
			}
		}
		Class[] ifcs = getProxiedInterfaces();
		if (ifcs.length == 1) {
			return ifcs[0];
		}
		else if (ifcs.length > 1) {
			return createCompositeInterface(ifcs);
		}
		else if (this.targetName != null && this.beanFactory != null) {
			return this.beanFactory.getType(this.targetName);
		}
		else {
			return getTargetClass();
		}
	}

	public boolean isSingleton() {
		return this.singleton;
	}


	/**
	 * Create a composite interface Class for the given interfaces,
	 * implementing the given interfaces in one single Class.
	 * <p>The default implementation builds a JDK proxy class for the
	 * given interfaces.
	 * @param interfaces the interfaces to merge
	 * @return the merged interface as Class
	 * @see java.lang.reflect.Proxy#getProxyClass
	 */
	protected Class createCompositeInterface(Class[] interfaces) {
		return ClassUtils.createCompositeInterface(interfaces, this.beanClassLoader);
	}

	/**
	 * Return the singleton instance of this class's proxy object,
	 * lazily creating it if it hasn't been created already.
	 * @return the shared singleton proxy
	 */
	private synchronized Object getSingletonInstance() {
		if (this.singletonInstance == null) {
			this.targetSource = freshTargetSource();
			if (this.autodetectInterfaces && getProxiedInterfaces().length == 0 && !isProxyTargetClass()) {
				// Rely on AOP infrastructure to tell us what interfaces to proxy.
				Class targetClass = getTargetClass();
				if (targetClass == null) {
					throw new FactoryBeanNotInitializedException("Cannot determine target class for proxy");
				}
				setInterfaces(ClassUtils.getAllInterfacesForClass(targetClass, this.beanClassLoader));
			}
			// Initialize the shared singleton instance.
			super.setFrozen(this.freezeProxy);
			this.singletonInstance = getProxy(createAopProxy());
		}
		return this.singletonInstance;
	}

	/**
	 * Create a new prototype instance of this class's created proxy object,
	 * backed by an independent AdvisedSupport configuration.
	 * @return a totally independent proxy, whose advice we may manipulate in isolation
	 */
	private synchronized Object newPrototypeInstance() {
		// In the case of a prototype, we need to give the proxy
		// an independent instance of the configuration.
		// In this case, no proxy will have an instance of this object's configuration,
		// but will have an independent copy.
		if (logger.isTraceEnabled()) {
			logger.trace("Creating copy of prototype ProxyFactoryBean config: " + this);
		}

		ProxyCreatorSupport copy = new ProxyCreatorSupport(getAopProxyFactory());
		// The copy needs a fresh advisor chain, and a fresh TargetSource.
		TargetSource targetSource = freshTargetSource();
		copy.copyConfigurationFrom(this, targetSource, freshAdvisorChain());
		if (this.autodetectInterfaces && getProxiedInterfaces().length == 0 && !isProxyTargetClass()) {
			// Rely on AOP infrastructure to tell us what interfaces to proxy.
			copy.setInterfaces(
					ClassUtils.getAllInterfacesForClass(targetSource.getTargetClass(), this.beanClassLoader));
		}
		copy.setFrozen(this.freezeProxy);

		if (logger.isTraceEnabled()) {
			logger.trace("Using ProxyCreatorSupport copy: " + copy);
		}
		return getProxy(copy.createAopProxy());
	}

	/**
	 * Return the proxy object to expose.
	 * <p>The default implementation uses a getProxy call with
	 * the factory's bean class loader. Can be overridden to specify a
	 * custom class loader.
	 * @param aopProxy the prepared AopProxy instance to get the proxy from
	 * @return the proxy object to expose
	 * @see AopProxy#getProxy(ClassLoader)
	 */
	protected Object getProxy(AopProxy aopProxy) {
		return aopProxy.getProxy(this.beanClassLoader);
	}

	/**
	 * Check the interceptorNames list whether it contains a target name as final element.
	 * If found, remove the final name from the list and set it as targetName.
	 */
	private void checkInterceptorNames() {
		if (!ObjectUtils.isEmpty(this.interceptorNames)) {
			String finalName = this.interceptorNames[this.interceptorNames.length - 1];
			if (this.targetName == null && this.targetSource == EMPTY_TARGET_SOURCE) {
				// The last name in the chain may be an Advisor/Advice or a target/TargetSource.
				// Unfortunately we don't know; we must look at type of the bean.
				if (!finalName.endsWith(GLOBAL_SUFFIX) && !isNamedBeanAnAdvisorOrAdvice(finalName)) {
					// The target isn't an interceptor.
					this.targetName = finalName;
					if (logger.isDebugEnabled()) {
						logger.debug("Bean with name '" + finalName + "' concluding interceptor chain " +
								"is not an advisor class: treating it as a target or TargetSource");
					}
					String[] newNames = new String[this.interceptorNames.length - 1];
					System.arraycopy(this.interceptorNames, 0, newNames, 0, newNames.length);
					this.interceptorNames = newNames;
				}
			}
		}
	}

	/**
	 * Look at bean factory metadata to work out whether this bean name,
	 * which concludes the interceptorNames list, is an Advisor or Advice,
	 * or may be a target.
	 * @param beanName bean name to check
	 * @return <code>true if it's an Advisor or Advice
	 */
	private boolean isNamedBeanAnAdvisorOrAdvice(String beanName) {
		Class namedBeanClass = this.beanFactory.getType(beanName);
		if (namedBeanClass != null) {
			return (Advisor.class.isAssignableFrom(namedBeanClass) || Advice.class.isAssignableFrom(namedBeanClass));
		}
		// Treat it as an target bean if we can't tell.
		if (logger.isDebugEnabled()) {
			logger.debug("Could not determine type of bean with name '" + beanName +
					"' - assuming it is neither an Advisor nor an Advice");
		}
		return false;
	}

	/**
	 * Create the advisor (interceptor) chain. Aadvisors that are sourced
	 * from a BeanFactory will be refreshed each time a new prototype instance
	 * is added. Interceptors added programmatically through the factory API
	 * are unaffected by such changes.
	 */
	private synchronized void initializeAdvisorChain() throws AopConfigException, BeansException {
		if (this.advisorChainInitialized) {
			return;
		}

		if (!ObjectUtils.isEmpty(this.interceptorNames)) {
			if (this.beanFactory == null) {
				throw new IllegalStateException("No BeanFactory available anymore (probably due to serialization) " +
						"- cannot resolve interceptor names " + Arrays.asList(this.interceptorNames));
			}

			// Globals can't be last unless we specified a targetSource using the property...
			if (this.interceptorNames[this.interceptorNames.length - 1].endsWith(GLOBAL_SUFFIX) &&
					this.targetName == null && this.targetSource == EMPTY_TARGET_SOURCE) {
				throw new AopConfigException("Target required after globals");
			}

			// Materialize interceptor chain from bean names.
			for (int i = 0; i < this.interceptorNames.length; i++) {
				String name = this.interceptorNames[i];
				if (logger.isTraceEnabled()) {
					logger.trace("Configuring advisor or advice '" + name + "'");
				}

				if (name.endsWith(GLOBAL_SUFFIX)) {
					if (!(this.beanFactory instanceof ListableBeanFactory)) {
						throw new AopConfigException(
								"Can only use global advisors or interceptors with a ListableBeanFactory");
					}
					addGlobalAdvisor((ListableBeanFactory) this.beanFactory,
							name.substring(0, name.length() - GLOBAL_SUFFIX.length()));
				}

				else {
					// If we get here, we need to add a named interceptor.
					// We must check if it's a singleton or prototype.
					Object advice = null;
					if (this.singleton || this.beanFactory.isSingleton(this.interceptorNames[i])) {
						// Add the real Advisor/Advice to the chain.
						advice = this.beanFactory.getBean(this.interceptorNames[i]);
					}
					else {
						// It's a prototype Advice or Advisor: replace with a prototype.
						// Avoid unnecessary creation of prototype bean just for advisor chain initialization.
						advice = new PrototypePlaceholderAdvisor(this.interceptorNames[i]);
					}
					addAdvisorOnChainCreation(advice, this.interceptorNames[i]);
				}
			}
		}

		this.advisorChainInitialized = true;
	}


	/**
	 * Return an independent advisor chain.
	 * We need to do this every time a new prototype instance is returned,
	 * to return distinct instances of prototype Advisors and Advices.
	 */
	private List freshAdvisorChain() {		
		Advisor[] advisors = getAdvisors();
		List freshAdvisors = new ArrayList(advisors.length);

		for (int i = 0; i < advisors.length; i++) {
			if (advisors[i] instanceof PrototypePlaceholderAdvisor) {
				PrototypePlaceholderAdvisor pa = (PrototypePlaceholderAdvisor) advisors[i];
				if (logger.isDebugEnabled()) {
					logger.debug("Refreshing bean named '" + pa.getBeanName() + "'");
				}
				// Replace the placeholder with a fresh prototype instance resulting
				// from a getBean() lookup
				if (this.beanFactory == null) {
					throw new IllegalStateException("No BeanFactory available anymore (probably due to serialization) " +
							"- cannot resolve prototype advisor '" + pa.getBeanName() + "'");
				}
				Object bean = this.beanFactory.getBean(pa.getBeanName());
				Advisor refreshedAdvisor = namedBeanToAdvisor(bean);
				freshAdvisors.add(refreshedAdvisor);
			}
			else {
				// Add the shared instance.
				freshAdvisors.add(advisors[i]);
			}
		}
		return freshAdvisors;
	}

	/**
	 * Add all global interceptors and pointcuts.
	 */
	private void addGlobalAdvisor(ListableBeanFactory beanFactory, String prefix) {
		String[] globalAdvisorNames =
				BeanFactoryUtils.beanNamesForTypeIncludingAncestors(beanFactory, Advisor.class);
		String[] globalInterceptorNames =
				BeanFactoryUtils.beanNamesForTypeIncludingAncestors(beanFactory, Interceptor.class);
		List beans = new ArrayList(globalAdvisorNames.length + globalInterceptorNames.length);
		Map names = new HashMap();
		for (int i = 0; i < globalAdvisorNames.length; i++) {
			String name = globalAdvisorNames[i];
			Object bean = beanFactory.getBean(name);
			beans.add(bean);
			names.put(bean, name);
		}
		for (int i = 0; i < globalInterceptorNames.length; i++) {
			String name = globalInterceptorNames[i];
			Object bean = beanFactory.getBean(name);
			beans.add(bean);
			names.put(bean, name);
		}
		Collections.sort(beans, new OrderComparator());
		for (Iterator it = beans.iterator(); it.hasNext();) {
			Object bean = it.next();
			String name = (String) names.get(bean);
			if (name.startsWith(prefix)) {
				addAdvisorOnChainCreation(bean, name);
			}
		}
	}

	/**
	 * Invoked when advice chain is created.
	 * <p>Add the given advice, advisor or object to the interceptor list.
	 * Because of these three possibilities, we can't type the signature
	 * more strongly.
	 * @param next advice, advisor or target object
	 * @param name bean name from which we obtained this object in our owning
	 * bean factory
	 */
	private void addAdvisorOnChainCreation(Object next, String name) {
		// We need to convert to an Advisor if necessary so that our source reference
		// matches what we find from superclass interceptors.
		Advisor advisor = namedBeanToAdvisor(next);
		if (logger.isTraceEnabled()) {
			logger.trace("Adding advisor with name '" + name + "'");
		}			
		addAdvisor((Advisor) advisor);
	}
	
	/**
	 * Return a TargetSource to use when creating a proxy. If the target was not
	 * specified at the end of the interceptorNames list, the TargetSource will be
	 * this class's TargetSource member. Otherwise, we get the target bean and wrap
	 * it in a TargetSource if necessary.
	 */
	private TargetSource freshTargetSource() {
		if (this.targetName == null) {
			if (logger.isTraceEnabled()) {
				logger.trace("Not refreshing target: Bean name not specified in 'interceptorNames'.");
			}
			return this.targetSource;
		}
		else {
			if (this.beanFactory == null) {
				throw new IllegalStateException("No BeanFactory available anymore (probably due to serialization) " +
						"- cannot resolve target with name '" + this.targetName + "'");
			}
			if (logger.isDebugEnabled()) {
				logger.debug("Refreshing target with name '" + this.targetName + "'");
			}
			Object target = this.beanFactory.getBean(this.targetName);
			return (target instanceof TargetSource ? (TargetSource) target : new SingletonTargetSource(target));
		}
	}

	/**
	 * Convert the following object sourced from calling getBean() on a name in the
	 * interceptorNames array to an Advisor or TargetSource.
	 */
	private Advisor namedBeanToAdvisor(Object next) {
		try {
			return this.advisorAdapterRegistry.wrap(next);
		}
		catch (UnknownAdviceTypeException ex) {
			// We expected this to be an Advisor or Advice,
			// but it wasn't. This is a configuration error.
			throw new AopConfigException("Unknown advisor type " + next.getClass() +
					"; Can only include Advisor or Advice type beans in interceptorNames chain except for last entry," +
					"which may also be target or TargetSource", ex);
		}
	}

	/**
	 * Blow away and recache singleton on an advice change.
	 */
	protected void adviceChanged() {
		super.adviceChanged();
		if (this.singleton) {
			logger.debug("Advice has changed; recaching singleton instance");
			synchronized (this) {
				this.singletonInstance = null;
			}
		}
	}


	//---------------------------------------------------------------------
	// Serialization support
	//---------------------------------------------------------------------

	private void readObject(ObjectInputStream ois) throws IOException, ClassNotFoundException {
		// Rely on default serialization; just initialize state after deserialization.
		ois.defaultReadObject();

		// Initialize transient fields.
		this.beanClassLoader = ClassUtils.getDefaultClassLoader();
	}


	/**
	 * Used in the interceptor chain where we need to replace a bean with a prototype
	 * on creating a proxy.
	 */
	private static class PrototypePlaceholderAdvisor implements Advisor, Serializable {

		private final String beanName;

		private final String message;
		
		public PrototypePlaceholderAdvisor(String beanName) {
			this.beanName = beanName;
			this.message = "Placeholder for prototype Advisor/Advice with bean name '" + beanName + "'";
		}
		
		public String getBeanName() {
			return beanName;
		}
		
		public Advice getAdvice() {
			throw new UnsupportedOperationException("Cannot invoke methods: " + this.message);
		}
		
		public boolean isPerInstance() {
			throw new UnsupportedOperationException("Cannot invoke methods: " + this.message);
		}
		
		public String toString() {
			return this.message;
		}
	}

}