/*
 * Copyright 2002-2018 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.lang.reflect.AccessibleObject;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;

import org.springframework.aop.ProxyMethodInvocation;
import org.springframework.aop.support.AopUtils;
import org.springframework.core.BridgeMethodResolver;
import org.springframework.lang.Nullable;

Spring's implementation of the AOP Alliance MethodInvocation interface, implementing the extended ProxyMethodInvocation interface. 
Invokes the target object using reflection. Subclasses can override the invokeJoinpoint() method to change this behavior, so this is also a useful base class for more specialized MethodInvocation implementations. 
It is possible to clone an invocation, to invoke proceed() repeatedly (once per clone), using the invocableClone() method. It is also possible to attach custom attributes to the invocation, using the setUserAttribute / getUserAttribute methods. 
NOTE: This class is considered internal and should not be directly accessed. The sole reason for it being public is compatibility with existing framework integrations (e.g. Pitchfork). For any other purposes, use the ProxyMethodInvocation interface instead. 
Author:
Rod Johnson, Juergen Hoeller, Adrian Colyer
See Also:
invokeJoinpoint
proceed
invocableClone
setUserAttribute
getUserAttribute/**
 * Spring's implementation of the AOP Alliance
 * {@link org.aopalliance.intercept.MethodInvocation} interface,
 * implementing the extended
 * {@link org.springframework.aop.ProxyMethodInvocation} interface.
 *
 * <p>Invokes the target object using reflection. Subclasses can override the
 * {@link #invokeJoinpoint()} method to change this behavior, so this is also
 * a useful base class for more specialized MethodInvocation implementations.
 *
 * <p>It is possible to clone an invocation, to invoke {@link #proceed()}
 * repeatedly (once per clone), using the {@link #invocableClone()} method.
 * It is also possible to attach custom attributes to the invocation,
 * using the {@link #setUserAttribute} / {@link #getUserAttribute} methods.
 *
 * <p><b>NOTE:</b> This class is considered internal and should not be
 * directly accessed. The sole reason for it being public is compatibility
 * with existing framework integrations (e.g. Pitchfork). For any other
 * purposes, use the {@link ProxyMethodInvocation} interface instead.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @author Adrian Colyer
 * @see #invokeJoinpoint
 * @see #proceed
 * @see #invocableClone
 * @see #setUserAttribute
 * @see #getUserAttribute
 */
public class ReflectiveMethodInvocation implements ProxyMethodInvocation, Cloneable {

	protected final Object proxy;

	@Nullable
	protected final Object target;

	protected final Method method;

	protected Object[] arguments = new Object[0];

	@Nullable
	private final Class<?> targetClass;

	
Lazily initialized map of user-specific attributes for this invocation.
/**
	 * Lazily initialized map of user-specific attributes for this invocation.
	 */
	@Nullable
	private Map<String, Object> userAttributes;

	
List of MethodInterceptor and InterceptorAndDynamicMethodMatcher
that need dynamic checks.
/**
	 * List of MethodInterceptor and InterceptorAndDynamicMethodMatcher
	 * that need dynamic checks.
	 */
	protected final List<?> interceptorsAndDynamicMethodMatchers;

	
Index from 0 of the current interceptor we're invoking.
-1 until we invoke: then the current interceptor.
/**
	 * Index from 0 of the current interceptor we're invoking.
	 * -1 until we invoke: then the current interceptor.
	 */
	private int currentInterceptorIndex = -1;


	
Construct a new ReflectiveMethodInvocation with the given arguments.
Params:
proxy – the proxy object that the invocation was made on
target – the target object to invoke
method – the method to invoke
arguments – the arguments to invoke the method with
targetClass – the target class, for MethodMatcher invocations
interceptorsAndDynamicMethodMatchers – interceptors that should be applied,
along with any InterceptorAndDynamicMethodMatchers that need evaluation at runtime.
MethodMatchers included in this struct must already have been found to have matched
as far as was possibly statically. Passing an array might be about 10% faster,
but would complicate the code. And it would work only for static pointcuts./**
	 * Construct a new ReflectiveMethodInvocation with the given arguments.
	 * @param proxy the proxy object that the invocation was made on
	 * @param target the target object to invoke
	 * @param method the method to invoke
	 * @param arguments the arguments to invoke the method with
	 * @param targetClass the target class, for MethodMatcher invocations
	 * @param interceptorsAndDynamicMethodMatchers interceptors that should be applied,
	 * along with any InterceptorAndDynamicMethodMatchers that need evaluation at runtime.
	 * MethodMatchers included in this struct must already have been found to have matched
	 * as far as was possibly statically. Passing an array might be about 10% faster,
	 * but would complicate the code. And it would work only for static pointcuts.
	 */
	protected ReflectiveMethodInvocation(
			Object proxy, @Nullable Object target, Method method, @Nullable Object[] arguments,
			@Nullable Class<?> targetClass, List<Object> interceptorsAndDynamicMethodMatchers) {

		this.proxy = proxy;
		this.target = target;
		this.targetClass = targetClass;
		this.method = BridgeMethodResolver.findBridgedMethod(method);
		this.arguments = AopProxyUtils.adaptArgumentsIfNecessary(method, arguments);
		this.interceptorsAndDynamicMethodMatchers = interceptorsAndDynamicMethodMatchers;
	}


	@Override
	public final Object getProxy() {
		return this.proxy;
	}

	@Override
	@Nullable
	public final Object getThis() {
		return this.target;
	}

	@Override
	public final AccessibleObject getStaticPart() {
		return this.method;
	}

	
Return the method invoked on the proxied interface.
May or may not correspond with a method invoked on an underlying
implementation of that interface.
/**
	 * Return the method invoked on the proxied interface.
	 * May or may not correspond with a method invoked on an underlying
	 * implementation of that interface.
	 */
	@Override
	public final Method getMethod() {
		return this.method;
	}

	@Override
	public final Object[] getArguments() {
		return this.arguments;
	}

	@Override
	public void setArguments(Object... arguments) {
		this.arguments = arguments;
	}


	@Override
	@Nullable
	public Object proceed() throws Throwable {
		//	We start with an index of -1 and increment early.
		if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {
			return invokeJoinpoint();
		}

		Object interceptorOrInterceptionAdvice =
				this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex);
		if (interceptorOrInterceptionAdvice instanceof InterceptorAndDynamicMethodMatcher) {
			// Evaluate dynamic method matcher here: static part will already have
			// been evaluated and found to match.
			InterceptorAndDynamicMethodMatcher dm =
					(InterceptorAndDynamicMethodMatcher) interceptorOrInterceptionAdvice;
			Class<?> targetClass = (this.targetClass != null ? this.targetClass : this.method.getDeclaringClass());
			if (dm.methodMatcher.matches(this.method, targetClass, this.arguments)) {
				return dm.interceptor.invoke(this);
			}
			else {
				// Dynamic matching failed.
				// Skip this interceptor and invoke the next in the chain.
				return proceed();
			}
		}
		else {
			// It's an interceptor, so we just invoke it: The pointcut will have
			// been evaluated statically before this object was constructed.
			return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);
		}
	}

	
Invoke the joinpoint using reflection.
Subclasses can override this to use custom invocation.
Throws:
Throwable – if invoking the joinpoint resulted in an exception
Returns:
the return value of the joinpoint/**
	 * Invoke the joinpoint using reflection.
	 * Subclasses can override this to use custom invocation.
	 * @return the return value of the joinpoint
	 * @throws Throwable if invoking the joinpoint resulted in an exception
	 */
	@Nullable
	protected Object invokeJoinpoint() throws Throwable {
		return AopUtils.invokeJoinpointUsingReflection(this.target, this.method, this.arguments);
	}


	
This implementation returns a shallow copy of this invocation object,
including an independent copy of the original arguments array.
We want a shallow copy in this case: We want to use the same interceptor
chain and other object references, but we want an independent value for the
current interceptor index.
See Also:
clone.clone()/**
	 * This implementation returns a shallow copy of this invocation object,
	 * including an independent copy of the original arguments array.
	 * <p>We want a shallow copy in this case: We want to use the same interceptor
	 * chain and other object references, but we want an independent value for the
	 * current interceptor index.
	 * @see java.lang.Object#clone()
	 */
	@Override
	public MethodInvocation invocableClone() {
		Object[] cloneArguments = this.arguments;
		if (this.arguments.length > 0) {
			// Build an independent copy of the arguments array.
			cloneArguments = new Object[this.arguments.length];
			System.arraycopy(this.arguments, 0, cloneArguments, 0, this.arguments.length);
		}
		return invocableClone(cloneArguments);
	}

	
This implementation returns a shallow copy of this invocation object,
using the given arguments array for the clone.
We want a shallow copy in this case: We want to use the same interceptor
chain and other object references, but we want an independent value for the
current interceptor index.
See Also:
clone.clone()/**
	 * This implementation returns a shallow copy of this invocation object,
	 * using the given arguments array for the clone.
	 * <p>We want a shallow copy in this case: We want to use the same interceptor
	 * chain and other object references, but we want an independent value for the
	 * current interceptor index.
	 * @see java.lang.Object#clone()
	 */
	@Override
	public MethodInvocation invocableClone(Object... arguments) {
		// Force initialization of the user attributes Map,
		// for having a shared Map reference in the clone.
		if (this.userAttributes == null) {
			this.userAttributes = new HashMap<>();
		}

		// Create the MethodInvocation clone.
		try {
			ReflectiveMethodInvocation clone = (ReflectiveMethodInvocation) clone();
			clone.arguments = arguments;
			return clone;
		}
		catch (CloneNotSupportedException ex) {
			throw new IllegalStateException(
					"Should be able to clone object of type [" + getClass() + "]: " + ex);
		}
	}


	@Override
	public void setUserAttribute(String key, @Nullable Object value) {
		if (value != null) {
			if (this.userAttributes == null) {
				this.userAttributes = new HashMap<>();
			}
			this.userAttributes.put(key, value);
		}
		else {
			if (this.userAttributes != null) {
				this.userAttributes.remove(key);
			}
		}
	}

	@Override
	@Nullable
	public Object getUserAttribute(String key) {
		return (this.userAttributes != null ? this.userAttributes.get(key) : null);
	}

	
Return user attributes associated with this invocation.
This method provides an invocation-bound alternative to a ThreadLocal.
This map is initialized lazily and is not used in the AOP framework itself.
Returns:
any user attributes associated with this invocation (never null)/**
	 * Return user attributes associated with this invocation.
	 * This method provides an invocation-bound alternative to a ThreadLocal.
	 * <p>This map is initialized lazily and is not used in the AOP framework itself.
	 * @return any user attributes associated with this invocation
	 * (never {@code null})
	 */
	public Map<String, Object> getUserAttributes() {
		if (this.userAttributes == null) {
			this.userAttributes = new HashMap<>();
		}
		return this.userAttributes;
	}


	@Override
	public String toString() {
		// Don't do toString on target, it may be proxied.
		StringBuilder sb = new StringBuilder("ReflectiveMethodInvocation: ");
		sb.append(this.method).append("; ");
		if (this.target == null) {
			sb.append("target is null");
		}
		else {
			sb.append("target is of class [").append(this.target.getClass().getName()).append(']');
		}
		return sb.toString();
	}

}