<bean class="me.arganzheng.study.scope.FooUser" scope="request">
	<aop:scoped-proxy />
</bean>

public class FooService{

    @Autowired
    FooUser fooUser;
    
    ...
}

// ..ignore imports and comments..
public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport implements ConfigurableBeanFactory {
   
   ...

	//---------------------------------------------------------------------
	// Implementation of BeanFactory interface
	//---------------------------------------------------------------------

	...

	/**
	 * Return an instance, which may be shared or independent, of the specified bean.
	 * @param name the name of the bean to retrieve
	 * @param requiredType the required type of the bean to retrieve
	 * @param args arguments to use if creating a prototype using explicit arguments to a
	 * static factory method. It is invalid to use a non-null args value in any other case.
	 * @param typeCheckOnly whether the instance is obtained for a type check,
	 * not for actual use
	 * @return an instance of the bean
	 * @throws BeansException if the bean could not be created
	 */
	@SuppressWarnings("unchecked")
	protected <T> T doGetBean(
			final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
			throws BeansException {

		final String beanName = transformedBeanName(name);
		Object bean;

		// Eagerly check singleton cache for manually registered singletons.
		Object sharedInstance = getSingleton(beanName);
		if (sharedInstance != null && args == null) {
			if (logger.isDebugEnabled()) {
				if (isSingletonCurrentlyInCreation(beanName)) {
					logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +
							"' that is not fully initialized yet - a consequence of a circular reference");
				}
				else {
					logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
				}
			}
			bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
		}

		else {
			// Fail if we're already creating this bean instance:
			// We're assumably within a circular reference.
			if (isPrototypeCurrentlyInCreation(beanName)) {
				throw new BeanCurrentlyInCreationException(beanName);
			}

			// Check if bean definition exists in this factory.
			BeanFactory parentBeanFactory = getParentBeanFactory();
			if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
				// Not found -> check parent.
				String nameToLookup = originalBeanName(name);
				if (args != null) {
					// Delegation to parent with explicit args.
					return (T) parentBeanFactory.getBean(nameToLookup, args);
				}
				else {
					// No args -> delegate to standard getBean method.
					return parentBeanFactory.getBean(nameToLookup, requiredType);
				}
			}

			if (!typeCheckOnly) {
				markBeanAsCreated(beanName);
			}

			final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
			checkMergedBeanDefinition(mbd, beanName, args);

			// Guarantee initialization of beans that the current bean depends on.
			String[] dependsOn = mbd.getDependsOn();
			if (dependsOn != null) {
				for (String dependsOnBean : dependsOn) {
					getBean(dependsOnBean);
					registerDependentBean(dependsOnBean, beanName);
				}
			}

			// Create bean instance.
			if (mbd.isSingleton()) {
				sharedInstance = getSingleton(beanName, new ObjectFactory() {
					public Object getObject() throws BeansException {
						try {
							return createBean(beanName, mbd, args);
						}
						catch (BeansException ex) {
							// Explicitly remove instance from singleton cache: It might have been put there
							// eagerly by the creation process, to allow for circular reference resolution.
							// Also remove any beans that received a temporary reference to the bean.
							destroySingleton(beanName);
							throw ex;
						}
					}
				});
				bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
			}

			else if (mbd.isPrototype()) {
				// It's a prototype -> create a new instance.
				Object prototypeInstance = null;
				try {
					beforePrototypeCreation(beanName);
					prototypeInstance = createBean(beanName, mbd, args);
				}
				finally {
					afterPrototypeCreation(beanName);
				}
				bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
			}

							else {
				String scopeName = mbd.getScope();
				final Scope scope = this.scopes.get(scopeName);
				if (scope == null) {
					throw new IllegalStateException("No Scope registered for scope '" + scopeName + "'");
				}
				try {
					Object scopedInstance = scope.get(beanName, new ObjectFactory() {
						public Object getObject() throws BeansException {
							beforePrototypeCreation(beanName);
							try {
								return createBean(beanName, mbd, args);
							}
							finally {
								afterPrototypeCreation(beanName);
							}
						}
					});
					bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
				}
				catch (IllegalStateException ex) {
					throw new BeanCreationException(beanName,
							"Scope '" + scopeName + "' is not active for the current thread; " +
							"consider defining a scoped proxy for this bean if you intend to refer to it from a singleton",
							ex);
				}
			}
		}

		// Check if required type matches the type of the actual bean instance.
		if (requiredType != null && bean != null && !requiredType.isAssignableFrom(bean.getClass())) {
			try {
				return getTypeConverter().convertIfNecessary(bean, requiredType);
			}
			catch (TypeMismatchException ex) {
				if (logger.isDebugEnabled()) {
					logger.debug("Failed to convert bean '" + name + "' to required type [" +
							ClassUtils.getQualifiedName(requiredType) + "]", ex);
				}
				throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
			}
		}
		return (T) bean;
	}

    ...

}

else {
    String scopeName = mbd.getScope();
	final Scope scope = this.scopes.get(scopeName);
	if (scope == null) {
		throw new IllegalStateException("No Scope registered for scope '" + scopeName + "'");
	}
	try {
		Object scopedInstance = scope.get(beanName, new ObjectFactory() {
	    	public Object getObject() throws BeansException {
				beforePrototypeCreation(beanName);
		    		try {
						return createBean(beanName, mbd, args);
					}
					finally {
						afterPrototypeCreation(beanName);
					}
			    }
			});
		bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
	}
	catch (IllegalStateException ex) {
		throw new BeanCreationException(beanName, "Scope '" + scopeName + "'" is not active for the current thread; " + 
		"consider defining a scoped proxy for this bean if you intend to refer to it from a singleton",	ex);
	}
}

String scopeName = mbd.getScope();
final Scope scope = this.scopes.get(scopeName);

package org.springframework.beans.factory.config;

import org.springframework.beans.factory.ObjectFactory;

public interface Scope {

	Object get(String name, ObjectFactory<?> objectFactory);

	Object remove(String name);

	void registerDestructionCallback(String name, Runnable callback);

	Object resolveContextualObject(String key);

	String getConversationId();
}

package org.springframework.web.context.request;

import org.springframework.beans.factory.ObjectFactory;
import org.springframework.beans.factory.config.Scope;

public abstract class AbstractRequestAttributesScope implements Scope {

	public Object get(String name, ObjectFactory objectFactory) {
		RequestAttributes attributes = RequestContextHolder.currentRequestAttributes();
		Object scopedObject = attributes.getAttribute(name, getScope());
		if (scopedObject == null) {
			scopedObject = objectFactory.getObject();
			attributes.setAttribute(name, scopedObject, getScope());
		}
		return scopedObject;
	}

	public Object remove(String name) {
		RequestAttributes attributes = RequestContextHolder.currentRequestAttributes();
		Object scopedObject = attributes.getAttribute(name, getScope());
		if (scopedObject != null) {
			attributes.removeAttribute(name, getScope());
			return scopedObject;
		}
		else {
			return null;
		}
	}

	public void registerDestructionCallback(String name, Runnable callback) {
		RequestAttributes attributes = RequestContextHolder.currentRequestAttributes();
		attributes.registerDestructionCallback(name, callback, getScope());
	}

	public Object resolveContextualObject(String key) {
		RequestAttributes attributes = RequestContextHolder.currentRequestAttributes();
		return attributes.resolveReference(key);
	}


	/**
	 * Template method that determines the actual target scope.
	 * @return the target scope, in the form of an appropriate
	 * {@link RequestAttributes} constant
	 * @see RequestAttributes#SCOPE_REQUEST
	 * @see RequestAttributes#SCOPE_SESSION
	 * @see RequestAttributes#SCOPE_GLOBAL_SESSION
	 */
	protected abstract int getScope();

}

package org.springframework.web.context.request;

public class RequestScope extends AbstractRequestAttributesScope {

	@Override
	protected int getScope() {
		return RequestAttributes.SCOPE_REQUEST;
	}

	public String getConversationId() {
		return null;
	}

}

package org.springframework.web.context.request;

import org.springframework.beans.factory.ObjectFactory;

public class SessionScope extends AbstractRequestAttributesScope {

	private final int scope;


	/**
	 * Create a new SessionScope, storing attributes in a locally
	 * isolated session (or default session, if there is no distinction
	 * between a global session and a component-specific session).
	 */
	public SessionScope() {
		this.scope = RequestAttributes.SCOPE_SESSION;
	}

	/**
	 * Create a new SessionScope, specifying whether to store attributes
	 * in the global session, provided that such a distinction is available.
	 * <p>This distinction is important for Portlet environments, where there
	 * are two notions of a session: "portlet scope" and "application scope".
	 * If this flag is on, objects will be put into the "application scope" session;
	 * else they will end up in the "portlet scope" session (the typical default).
	 * <p>In a Servlet environment, this flag is effectively ignored.
	 * @param globalSession <code>true</code> in case of the global session as target;
	 * <code>false</code> in case of a component-specific session as target
	 * @see org.springframework.web.portlet.context.PortletRequestAttributes
	 * @see org.springframework.web.context.request.ServletRequestAttributes
	 */
	public SessionScope(boolean globalSession) {
		this.scope = (globalSession ? RequestAttributes.SCOPE_GLOBAL_SESSION : RequestAttributes.SCOPE_SESSION);
	}


	@Override
	protected int getScope() {
		return this.scope;
	}

	public String getConversationId() {
		return RequestContextHolder.currentRequestAttributes().getSessionId();
	}

	@Override
	public Object get(String name, ObjectFactory objectFactory) {
		Object mutex = RequestContextHolder.currentRequestAttributes().getSessionMutex();
		synchronized (mutex) {
			return super.get(name, objectFactory);
		}
	}

	@Override
	public Object remove(String name) {
		Object mutex = RequestContextHolder.currentRequestAttributes().getSessionMutex();
		synchronized (mutex) {
			return super.remove(name);
		}
	}
}

public Object get(String name, ObjectFactory objectFactory) {
	RequestAttributes attributes = RequestContextHolder.currentRequestAttributes();
	Object scopedObject = attributes.getAttribute(name, getScope());
	if (scopedObject == null) {
		scopedObject = objectFactory.getObject();
		attributes.setAttribute(name, scopedObject, getScope());
	}
	return scopedObject;
}

package org.springframework.web.context.request;

/**
 * Abstraction for accessing attribute objects associated with a request.
 * Supports access to request-scoped attributes as well as to session-scoped
 * attributes, with the optional notion of a "global session".
 *
 * <p>Can be implemented for any kind of request/session mechanism,
 * in particular for servlet requests and portlet requests.
 *
 * @see ServletRequestAttributes
 * @see org.springframework.web.portlet.context.PortletRequestAttributes
 */
public interface RequestAttributes {

	int SCOPE_REQUEST = 0;

	int SCOPE_SESSION = 1;

	int SCOPE_GLOBAL_SESSION = 2;

	String REFERENCE_REQUEST = "request";

	String REFERENCE_SESSION = "session";


	Object getAttribute(String name, int scope);

	void setAttribute(String name, Object value, int scope);

	void removeAttribute(String name, int scope);

	String[] getAttributeNames(int scope);

	void registerDestructionCallback(String name, Runnable callback, int scope);

	Object resolveReference(String key);

	String getSessionId();
	
	Object getSessionMutex();
}

package org.springframework.web.context.request;

import java.util.LinkedHashMap;
import java.util.Map;

import org.springframework.util.Assert;

/**
 * Abstract support class for RequestAttributes implementations,
 * offering a request completion mechanism for request-specific destruction
 * callbacks and for updating accessed session attributes.
 */
public abstract class AbstractRequestAttributes implements RequestAttributes {
    ...
} >

package org.springframework.web.context.request;

import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

import org.springframework.util.Assert;
import org.springframework.util.StringUtils;
import org.springframework.web.util.WebUtils;

/**
 * Servlet-based implementation of the {@link RequestAttributes} interface.
 *
 * <p>Accesses objects from servlet request and HTTP session scope,
 * with no distinction between "session" and "global session".
 *
 * @see javax.servlet.ServletRequest#getAttribute
 * @see javax.servlet.http.HttpSession#getAttribute
 */
public class ServletRequestAttributes extends AbstractRequestAttributes {

	/**
	 * Constant identifying the {@link String} prefixed to the name of a
	 * destruction callback when it is stored in a {@link HttpSession}.
	 */
	public static final String DESTRUCTION_CALLBACK_NAME_PREFIX =
			ServletRequestAttributes.class.getName() + ".DESTRUCTION_CALLBACK.";


	private final HttpServletRequest request;

	private volatile HttpSession session;

	private final Map<String, Object> sessionAttributesToUpdate = new HashMap<String, Object>();


	/**
	 * Create a new ServletRequestAttributes instance for the given request.
	 * @param request current HTTP request
	 */
	public ServletRequestAttributes(HttpServletRequest request) {
		Assert.notNull(request, "Request must not be null");
		this.request = request;
	}


	/**
	 * Exposes the native {@link HttpServletRequest} that we're wrapping.
	 */
	public final HttpServletRequest getRequest() {
		return this.request;
	}

	/**
	 * Exposes the {@link HttpSession} that we're wrapping.
	 * @param allowCreate whether to allow creation of a new session if none exists yet
	 */
	protected final HttpSession getSession(boolean allowCreate) {
		if (isRequestActive()) {
			return this.request.getSession(allowCreate);
		}
		else {
			// Access through stored session reference, if any...
			if (this.session == null && allowCreate) {
				throw new IllegalStateException(
						"No session found and request already completed - cannot create new session!");
			}
			return this.session;
		}
	}


	public Object getAttribute(String name, int scope) {
		if (scope == SCOPE_REQUEST) {
			if (!isRequestActive()) {
				throw new IllegalStateException(
						"Cannot ask for request attribute - request is not active anymore!");
			}
			return this.request.getAttribute(name);
		}
		else {
			HttpSession session = getSession(false);
			if (session != null) {
				try {
					Object value = session.getAttribute(name);
					if (value != null) {
						synchronized (this.sessionAttributesToUpdate) {
							this.sessionAttributesToUpdate.put(name, value);
						}
					}
					return value;
				}
				catch (IllegalStateException ex) {
					// Session invalidated - shouldn't usually happen.
				}
			}
			return null;
		}
	}

	public void setAttribute(String name, Object value, int scope) {
		if (scope == SCOPE_REQUEST) {
			if (!isRequestActive()) {
				throw new IllegalStateException(
						"Cannot set request attribute - request is not active anymore!");
			}
			this.request.setAttribute(name, value);
		}
		else {
			HttpSession session = getSession(true);
			synchronized (this.sessionAttributesToUpdate) {
				this.sessionAttributesToUpdate.remove(name);
			}
			session.setAttribute(name, value);
		}
	}

	public void removeAttribute(String name, int scope) {
		if (scope == SCOPE_REQUEST) {
			if (isRequestActive()) {
				this.request.removeAttribute(name);
				removeRequestDestructionCallback(name);
			}
		}
		else {
			HttpSession session = getSession(false);
			if (session != null) {
				synchronized (this.sessionAttributesToUpdate) {
					this.sessionAttributesToUpdate.remove(name);
				}
				try {
					session.removeAttribute(name);
					// Remove any registered destruction callback as well.
					session.removeAttribute(DESTRUCTION_CALLBACK_NAME_PREFIX + name);
				}
				catch (IllegalStateException ex) {
					// Session invalidated - shouldn't usually happen.
				}
			}
		}
	}

	@SuppressWarnings("unchecked")
	public String[] getAttributeNames(int scope) {
		if (scope == SCOPE_REQUEST) {
			if (!isRequestActive()) {
				throw new IllegalStateException(
						"Cannot ask for request attributes - request is not active anymore!");
			}
			return StringUtils.toStringArray(this.request.getAttributeNames());
		}
		else {
			HttpSession session = getSession(false);
			if (session != null) {
				try {
					return StringUtils.toStringArray(session.getAttributeNames());
				}
				catch (IllegalStateException ex) {
					// Session invalidated - shouldn't usually happen.
				}
			}
			return new String[0];
		}
	}

	public String getSessionId() {
		return getSession(true).getId();
	}

	public Object getSessionMutex() {
		return WebUtils.getSessionMutex(getSession(true));
	}

    ...
}

package org.springframework.web.context.request;

import javax.faces.context.FacesContext;

import org.springframework.core.NamedInheritableThreadLocal;
import org.springframework.core.NamedThreadLocal;
import org.springframework.util.ClassUtils;

/**
 * Holder class to expose the web request in the form of a thread-bound
 * {@link RequestAttributes} object. The request will be inherited
 * by any child threads spawned by the current thread if the
 * <code>inheritable<code> flag is set to <code>true</code>.
 *
 * <p>Use {@link RequestContextListener} or
 * {@link org.springframework.web.filter.RequestContextFilter} to expose
 * the current web request. Note that
 * {@link org.springframework.web.servlet.DispatcherServlet} and
 * {@link org.springframework.web.portlet.DispatcherPortlet} already
 * expose the current request by default.
 *
 * @see RequestContextListener
 * @see org.springframework.web.filter.RequestContextFilter
 * @see org.springframework.web.servlet.DispatcherServlet
 * @see org.springframework.web.portlet.DispatcherPortlet
 */
public abstract class RequestContextHolder  {
	
	private static final boolean jsfPresent =
			ClassUtils.isPresent("javax.faces.context.FacesContext", RequestContextHolder.class.getClassLoader());

	private static final ThreadLocal<RequestAttributes> requestAttributesHolder =
			new NamedThreadLocal<RequestAttributes>("Request attributes");

	private static final ThreadLocal<RequestAttributes> inheritableRequestAttributesHolder =
			new NamedInheritableThreadLocal<RequestAttributes>("Request context");


	public static void resetRequestAttributes() {
		requestAttributesHolder.remove();
		inheritableRequestAttributesHolder.remove();
	}

	public static void setRequestAttributes(RequestAttributes attributes) {
		setRequestAttributes(attributes, false);
	}

	public static void setRequestAttributes(RequestAttributes attributes, boolean inheritable) {
		if (attributes == null) {
			resetRequestAttributes();
		}
		else {
			if (inheritable) {
				inheritableRequestAttributesHolder.set(attributes);
				requestAttributesHolder.remove();
			}
			else {
				requestAttributesHolder.set(attributes);
				inheritableRequestAttributesHolder.remove();
			}
		}
	}

	public static RequestAttributes getRequestAttributes() {
		RequestAttributes attributes = requestAttributesHolder.get();
		if (attributes == null) {
			attributes = inheritableRequestAttributesHolder.get();
		}
		return attributes;
	}

	public static RequestAttributes currentRequestAttributes() throws IllegalStateException {
		RequestAttributes attributes = getRequestAttributes();
		if (attributes == null) {
			if (jsfPresent) {
				attributes = FacesRequestAttributesFactory.getFacesRequestAttributes();
			}
			if (attributes == null) {
				throw new IllegalStateException("No thread-bound request found: " +
						"Are you referring to request attributes outside of an actual web request, " +
						"or processing a request outside of the originally receiving thread? " +
						"If you are actually operating within a web request and still receive this message, " +
						"your code is probably running outside of DispatcherServlet/DispatcherPortlet: " +
						"In this case, use RequestContextListener or RequestContextFilter to expose the current request.");
			}
		}
		return attributes;
	}

	private static class FacesRequestAttributesFactory {

		public static RequestAttributes getFacesRequestAttributes() {
			FacesContext facesContext = FacesContext.getCurrentInstance();
			return (facesContext != null ? new FacesRequestAttributes(facesContext) : null);
		}
	}
}

package org.springframework.web.context.request;

import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
import javax.servlet.http.HttpServletRequest;

import org.springframework.context.i18n.LocaleContextHolder;

public class RequestContextListener implements ServletRequestListener {

	private static final String REQUEST_ATTRIBUTES_ATTRIBUTE =
			RequestContextListener.class.getName() + ".REQUEST_ATTRIBUTES";


	public void requestInitialized(ServletRequestEvent requestEvent) {
		if (!(requestEvent.getServletRequest() instanceof HttpServletRequest)) {
			throw new IllegalArgumentException(
					"Request is not an HttpServletRequest: " + requestEvent.getServletRequest());
		}
		HttpServletRequest request = (HttpServletRequest) requestEvent.getServletRequest();
		ServletRequestAttributes attributes = new ServletRequestAttributes(request);
		request.setAttribute(REQUEST_ATTRIBUTES_ATTRIBUTE, attributes);
		LocaleContextHolder.setLocale(request.getLocale());
		RequestContextHolder.setRequestAttributes(attributes);
	}

	public void requestDestroyed(ServletRequestEvent requestEvent) {
		ServletRequestAttributes attributes =
				(ServletRequestAttributes) requestEvent.getServletRequest().getAttribute(REQUEST_ATTRIBUTES_ATTRIBUTE);
		ServletRequestAttributes threadAttributes =
				(ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
		if (threadAttributes != null) {
			// We're assumably within the original request thread...
			if (attributes == null) {
				attributes = threadAttributes;
			}
			LocaleContextHolder.resetLocaleContext();
			RequestContextHolder.resetRequestAttributes();
		}
		if (attributes != null) {
			attributes.requestCompleted();
		}
	}

}

public Object get(String name, ObjectFactory objectFactory) {
	RequestAttributes attributes = RequestContextHolder.currentRequestAttributes();
	Object scopedObject = attributes.getAttribute(name, getScope());
	if (scopedObject == null) {
		scopedObject = objectFactory.getObject();
		attributes.setAttribute(name, scopedObject, getScope());
	}
	return scopedObject;
}

package org.springframework.aop.config;

import org.w3c.dom.Element;
import org.w3c.dom.Node;

import org.springframework.aop.scope.ScopedProxyUtils;
import org.springframework.beans.factory.config.BeanDefinitionHolder;
import org.springframework.beans.factory.parsing.BeanComponentDefinition;
import org.springframework.beans.factory.xml.BeanDefinitionDecorator;
import org.springframework.beans.factory.xml.ParserContext;

/**
 * {@link BeanDefinitionDecorator} responsible for parsing the
 * <code>&lt;aop:scoped-proxy/&gt;</code> tag.
 * @since 2.0
 */
class ScopedProxyBeanDefinitionDecorator implements BeanDefinitionDecorator {

	private static final String PROXY_TARGET_CLASS = "proxy-target-class";


	public BeanDefinitionHolder decorate(Node node, BeanDefinitionHolder definition, ParserContext parserContext) {
		boolean proxyTargetClass = true;
		if (node instanceof Element) {
			Element ele = (Element) node;
			if (ele.hasAttribute(PROXY_TARGET_CLASS)) {
				proxyTargetClass = Boolean.valueOf(ele.getAttribute(PROXY_TARGET_CLASS));
			}
		}
		
		// Register the original bean definition as it will be referenced by the scoped proxy
		// and is relevant for tooling (validation, navigation).
		BeanDefinitionHolder holder =
				ScopedProxyUtils.createScopedProxy(definition, parserContext.getRegistry(), proxyTargetClass);
		String targetBeanName = ScopedProxyUtils.getTargetBeanName(definition.getBeanName());
		parserContext.getReaderContext().fireComponentRegistered(
				new BeanComponentDefinition(definition.getBeanDefinition(), targetBeanName));
		return holder;
	}

}