cglib2aopproxy.java

spring 框架代码

	 * Interceptor for unadvised dynamic targets when the proxy needs exposing.
	 */
	private class DynamicUnadvisedExposedInterceptor implements MethodInterceptor, Serializable {

		public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
			Object oldProxy = null;
			Object target = advised.getTargetSource().getTarget();
			try {
				oldProxy = AopContext.setCurrentProxy(proxy);
				Object retVal = methodProxy.invoke(target, args);
				return massageReturnTypeIfNecessary(proxy, target, retVal);
			}
			finally {
				AopContext.setCurrentProxy(oldProxy);
				advised.getTargetSource().releaseTarget(target);
			}
		}
	}


	/**
	 * Dispatcher for a static target. Dispatcher is much faster than
	 * interceptor. This will be used whenever it can be determined that a
	 * method definitely does not return "this"
	 */
	private static class StaticDispatcher implements Dispatcher, Serializable {

		private Object target;

		public StaticDispatcher(Object target) {
			this.target = target;
		}

		public Object loadObject() {
			return this.target;
		}
	}


	/**
	 * Dispatcher for any methods declared on the Advised class.
	 */
	private class AdvisedDispatcher implements Dispatcher, Serializable {

		public Object loadObject() throws Exception {
			return advised;
		}
	}


	/**
	 * Dispatcher for the <code>equals</code> method.
	 * Ensures that the method call is always handled by this class.
	 */
	private static class EqualsInterceptor implements MethodInterceptor, Serializable {

		private final AdvisedSupport advised;

		public EqualsInterceptor(AdvisedSupport advised) {
			this.advised = advised;
		}

		public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) {
			Object other = args[0];
			if (proxy == other) {
				return Boolean.TRUE;
			}
			AdvisedSupport otherAdvised = null;
			if (other instanceof Factory) {
				Callback callback = ((Factory) other).getCallback(INVOKE_EQUALS);
				if (!(callback instanceof EqualsInterceptor)) {
					return Boolean.FALSE;
				}
				otherAdvised = ((EqualsInterceptor) callback).advised;
			}
			else {
				return Boolean.FALSE;
			}
			return (AopProxyUtils.equalsInProxy(this.advised, otherAdvised) ? Boolean.TRUE : Boolean.FALSE);
		}
	}


	/**
	 * Dispatcher for the <code>hashCode</code> method.
	 * Ensures that the method call is always handled by this class.
	 */
	private static class HashCodeInterceptor implements MethodInterceptor, Serializable {

		private final AdvisedSupport advised;

		public HashCodeInterceptor(AdvisedSupport advised) {
			this.advised = advised;
		}

		public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) {
			return new Integer(Cglib2AopProxy.class.hashCode());
		}
	}


	/**
	 * Interceptor used specifcally for advised methods on a frozen, static proxy.
	 */
	private static class FixedChainStaticTargetInterceptor implements MethodInterceptor, Serializable {

		private final List adviceChain;

		private final Object target;

		private final Class targetClass;

		public FixedChainStaticTargetInterceptor(List adviceChain, Object target, Class targetClass) {
			this.adviceChain = adviceChain;
			this.target = target;
			this.targetClass = targetClass;
		}

		public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
			Object retVal = null;
			MethodInvocation invocation = new CglibMethodInvocation(proxy, this.target, method, args,
					this.targetClass, this.adviceChain, methodProxy);
			// If we get here, we need to create a MethodInvocation.
			retVal = invocation.proceed();
			retVal = massageReturnTypeIfNecessary(proxy, this.target, retVal);
			return retVal;
		}
	}


	/**
	 * General purpose AOP callback. Used when the target is dynamic or when the
	 * proxy is not frozen.
	 */
	private class DynamicAdvisedInterceptor implements MethodInterceptor, Serializable {

		public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
			MethodInvocation invocation = null;
			Object oldProxy = null;
			boolean setProxyContext = false;
			Class targetClass = null;
			Object target = null;
			try {
				Object retVal = null;
				if (advised.exposeProxy) {
					// Make invocation available if necessary.
					oldProxy = AopContext.setCurrentProxy(proxy);
					setProxyContext = true;
				}
				// May be <code>null</code>. Get as late as possible to minimize the time we
				// "own" the target, in case it comes from a pool.
				target = getTarget();
				if (target != null) {
					targetClass = target.getClass();
				}
				List chain = advised.getAdvisorChainFactory().getInterceptorsAndDynamicInterceptionAdvice(
						advised, proxy, method, targetClass);
				// Check whether we only have one InvokerInterceptor: that is,
				// no real advice, but just reflective invocation of the target.
				if (chain.isEmpty() && Modifier.isPublic(method.getModifiers())) {
					// We can skip creating a MethodInvocation: just invoke the target directly.
					// Note that the final invoker must be an InvokerInterceptor, so we know
					// it does nothing but a reflective operation on the target, and no hot
					// swapping or fancy proxying.
					retVal = methodProxy.invoke(target, args);
				}
				else {
					// We need to create a method invocation...
					invocation = new CglibMethodInvocation(proxy, target, method, args,
							targetClass, chain, methodProxy);
					// If we get here, we need to create a MethodInvocation.
					retVal = invocation.proceed();
				}

				retVal = massageReturnTypeIfNecessary(proxy, target, retVal);
				return retVal;
			}
			finally {
				if (target != null) {
					releaseTarget(target);
				}
				if (setProxyContext) {
					// Restore old proxy.
					AopContext.setCurrentProxy(oldProxy);
				}
			}
		}

		/**
		 * CGLIB uses this to drive proxy creation.
		 */
		public int hashCode() {
			return advised.hashCode();
		}

		protected Object getTarget() throws Exception {
			return advised.getTargetSource().getTarget();
		}

		protected void releaseTarget(Object target) throws Exception {
			advised.getTargetSource().releaseTarget(target);
		}
	}


	/**
	 * Implementation of AOP Alliance MethodInvocation used by this AOP proxy.
	 */
	private static class CglibMethodInvocation extends ReflectiveMethodInvocation {

		private final MethodProxy methodProxy;

		private boolean protectedMethod;

		public CglibMethodInvocation(Object proxy, Object target, Method method, Object[] arguments,
				Class targetClass, List interceptorsAndDynamicMethodMatchers, MethodProxy methodProxy) {
			super(proxy, target, method, arguments, targetClass, interceptorsAndDynamicMethodMatchers);
			this.methodProxy = methodProxy;
			this.protectedMethod = Modifier.isProtected(method.getModifiers());
		}

		/**
		 * Gives a marginal performance improvement versus using reflection to
		 * invoke the target when invoking public methods.
		 */
		protected Object invokeJoinpoint() throws Throwable {
			if (this.protectedMethod) {
				return super.invokeJoinpoint();
			}
			else {
				return this.methodProxy.invoke(this.target, this.arguments);
			}
		}
	}


	/**
	 * CallbackFilter to assign Callbacks to methods.
	 */
	private class ProxyCallbackFilter implements CallbackFilter {

		private final AdvisedSupport advised;

		public ProxyCallbackFilter(AdvisedSupport advised) {
			this.advised = advised;
		}

		/**
		 * Implementation of CallbackFilter.accept() to return the index of the
		 * callback we need.
		 * <p>The callbacks for each proxy are built up of a set of fixed callbacks
		 * for general use and then a set of callbacks that are specific to a method
		 * for use on static targets with a fixed advice chain.
		 * <p>The callback used is determined thus:
		 * <dl>
		 * <dt>For exposed proxies</dt>
		 * <dd>Exposing the proxy requires code to execute before and after the
		 * method/chain invocation. This means we must use
		 * DynamicAdvisedInterceptor, since all other interceptors can avoid the
		 * need for a try/catch block</dd>
		 * <dt>For Object.finalize():</dt>
		 * <dd>No override for this method is used</dd>
		 * <dt>For equals():</dt>
		 * <dd>The EqualsInterceptor is used to redirect equals() calls to a
		 * special handler to this proxy.</dd>
		 * <dt>For methods on the Advised class:</dt>
		 * <dd>the AdvisedDispatcher is used to dispatch the call directly to
		 * the target</dd>
		 * <dt>For advised methods:</dt>
		 * <dd>If the target is static and the advice chain is frozen then a
		 * FixedChainStaticTargetInterceptor specific to the method is used to
		 * invoke the advice chain. Otherwise a DyanmicAdvisedInterceptor is
		 * used.</dd>
		 * <dt>For non-advised methods:</dt>
		 * <dd>Where it can be determined that the method will not return <code>this</code>
		 * or when <code>ProxyFactory.getExposeProxy()</code> returns <code>false</code>,
		 * then a Dispatcher is used. For static targets, the StaticDispatcher is used;
		 * and for dynamic targets, a DynamicUnadvisedInterceptor is used.
		 * If it possible for the method to return <code>this</code> then a
		 * StaticUnadvisedInterceptor is used for static targets - the
		 * DynamicUnadvisedInterceptor already considers this.</dd>
		 * </dl>
		 */
		public int accept(Method method) {
			if (method.getDeclaringClass() == Object.class && method.getName().equals("finalize")) {
				logger.debug("Found finalize() method - using NO_OVERRIDE");
				return NO_OVERRIDE;
			}
			if (method.getDeclaringClass() == Advised.class) {
				if (logger.isDebugEnabled()) {
					logger.debug("Method is declared on Advised interface: " + method);
				}
				return DISPATCH_ADVISED;
			}
			// We must always proxy equals, to direct calls to this
			if (AopUtils.isEqualsMethod(method)) {
				logger.debug("Found 'equals' method: " + method);
				return INVOKE_EQUALS;
			}
			// We must always calculate hashCode based on the proxy.
			if (AopUtils.isHashCodeMethod(method)) {
				logger.debug("Found 'hashCode' method: " + method);
				return INVOKE_HASHCODE;
			}
			Class targetClass = this.advised.getTargetSource().getTargetClass();
			// Proxy is not yet available, but that shouldn't matter.
			List chain = this.advised.getAdvisorChainFactory().getInterceptorsAndDynamicInterceptionAdvice(
					this.advised, null, method, targetClass);
			boolean haveAdvice = !chain.isEmpty();
			boolean exposeProxy = this.advised.isExposeProxy();
			boolean isStatic = this.advised.getTargetSource().isStatic();
			boolean isFrozen = this.advised.isFrozen();
			if (haveAdvice || !isFrozen) {
				// If exposing the proxy, then AOP_PROXY must be used.
				if (exposeProxy) {
					if (logger.isDebugEnabled()) {
						logger.debug("Must expose proxy on advised method: " + method);
					}
					return AOP_PROXY;
				}
				String key = method.toString();
				// Check to see if we have fixed interceptor to serve this method.
				// Else use the AOP_PROXY.
				if (isStatic && isFrozen && fixedInterceptorMap.containsKey(key)) {
					if (logger.isDebugEnabled()) {
						logger.debug("Method has advice and optimisations are enabled: " + method);
					}
					// We know that we are optimising so we can use the
					// FixedStaticChainInterceptors.
					int index = ((Integer) fixedInterceptorMap.get(key)).intValue();
					return (index + fixedInterceptorOffset);
				}
				else {
					if (logger.isDebugEnabled()) {
						logger.debug("Unable to apply any optimisations to advised method: " + method);
					}
					return AOP_PROXY;
				}
			}
			else {
				// See if the return type of the method is outside the class hierarchy
				// of the target type. If so we know it never needs to have return type
				// massage and can use a dispatcher.
				// If the proxy is being exposed, then must use the interceptor the
				// correct one is already configured. If the target is not static cannot
				// use a Dispatcher because the target can not then be released.
				if (exposeProxy || !isStatic) {
					return INVOKE_TARGET;
				}
				Class returnType = method.getReturnType();
				if (targetClass == returnType) {
					if (logger.isDebugEnabled()) {
						logger.debug("Method " + method +
								"has return type same as target type (may return this) - using INVOKE_TARGET");
					}
					return INVOKE_TARGET;
				}
				else if (returnType.isPrimitive() || !returnType.isAssignableFrom(targetClass)) {
					if (logger.isDebugEnabled()) {
						logger.debug("Method " + method +
								" has return type that ensures this cannot be returned- using DISPATCH_TARGET");
					}
					return DISPATCH_TARGET;
				}
				else {
					if (logger.isDebugEnabled()) {
						logger.debug("Method " + method +
								"has return type that is assignable from the target type (may return this) - " +
								"using INVOKE_TARGET");
					}
					return INVOKE_TARGET;
				}
			}
		}

		public boolean equals(Object other) {
			if (other == this) {
				return true;
			}
			if (!(other instanceof ProxyCallbackFilter)) {
				return false;
			}
			ProxyCallbackFilter otherCallbackFilter = (ProxyCallbackFilter) other;
			if (this.advised.isFrozen() != otherCallbackFilter.advised.isFrozen()) {
				return false;
			}
			if (this.advised.isExposeProxy() != otherCallbackFilter.advised.isExposeProxy()) {
				return false;
			}
			if (this.advised.getTargetSource().isStatic() !=
					otherCallbackFilter.advised.getTargetSource().isStatic()) {
				return false;
			}
			return (AopProxyUtils.equalsProxiedInterfaces(this.advised, otherCallbackFilter.advised) &&
					AopProxyUtils.equalsAdvisors(advised, otherCallbackFilter.advised));
		}

		public int hashCode() {
			return ProxyCallbackFilter.class.hashCode();
		}
	}


	/**
	 * Helper class that determines whether the CGLIB Enhancer
	 * supports the <code>setInterceptDuringConstruction</code> method
	 * (which it should as of CGLIB 2.1).
	 */
	private static class CglibUtils {

		private static boolean canSkipConstructorInterception;

		static {
			try {
				Enhancer.class.getMethod("setInterceptDuringConstruction", new Class[] {boolean.class});
				canSkipConstructorInterception = true;
			}
			catch (NoSuchMethodException ex) {
				canSkipConstructorInterception = false;
			}
		}

		public static boolean canSkipConstructorInterception() {
			return canSkipConstructorInterception;
		}
	}

}