/*
 * Copyright 2002-2020 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
 *
 *      https://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.aspectj.annotation;

import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.aspectj.lang.reflect.PerClauseKind;

import org.springframework.aop.Advisor;
import org.springframework.aop.aspectj.AspectJProxyUtils;
import org.springframework.aop.aspectj.SimpleAspectInstanceFactory;
import org.springframework.aop.framework.ProxyCreatorSupport;
import org.springframework.aop.support.AopUtils;
import org.springframework.core.annotation.AnnotationAwareOrderComparator;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;

AspectJ-based proxy factory, allowing for programmatic building
of proxies which include AspectJ aspects (code style as well
Java 5 annotation style).
Author:
Rob Harrop, Juergen Hoeller, Ramnivas Laddad
See Also:
addAspect(Object)
addAspect(Class<?>)
getProxy()
getProxy(ClassLoader)
ProxyFactory
Since:
2.0/**
 * AspectJ-based proxy factory, allowing for programmatic building
 * of proxies which include AspectJ aspects (code style as well
 * Java 5 annotation style).
 *
 * @author Rob Harrop
 * @author Juergen Hoeller
 * @author Ramnivas Laddad
 * @since 2.0
 * @see #addAspect(Object)
 * @see #addAspect(Class)
 * @see #getProxy()
 * @see #getProxy(ClassLoader)
 * @see org.springframework.aop.framework.ProxyFactory
 */
@SuppressWarnings("serial")
public class AspectJProxyFactory extends ProxyCreatorSupport {

	
Cache for singleton aspect instances. /** Cache for singleton aspect instances. */
	private static final Map<Class<?>, Object> aspectCache = new ConcurrentHashMap<>();

	private final AspectJAdvisorFactory aspectFactory = new ReflectiveAspectJAdvisorFactory();


	
Create a new AspectJProxyFactory.
/**
	 * Create a new AspectJProxyFactory.
	 */
	public AspectJProxyFactory() {
	}

	
Create a new AspectJProxyFactory.
Will proxy all interfaces that the given target implements.
Params:
target – the target object to be proxied/**
	 * Create a new AspectJProxyFactory.
	 * <p>Will proxy all interfaces that the given target implements.
	 * @param target the target object to be proxied
	 */
	public AspectJProxyFactory(Object target) {
		Assert.notNull(target, "Target object must not be null");
		setInterfaces(ClassUtils.getAllInterfaces(target));
		setTarget(target);
	}

	
Create a new AspectJProxyFactory. No target, only interfaces. Must add interceptors. /**
	 * Create a new {@code AspectJProxyFactory}.
	 * No target, only interfaces. Must add interceptors.
	 */
	public AspectJProxyFactory(Class<?>... interfaces) {
		setInterfaces(interfaces);
	}


	
Add the supplied aspect instance to the chain. The type of the aspect instance
supplied must be a singleton aspect. True singleton lifecycle is not honoured when
using this method - the caller is responsible for managing the lifecycle of any
aspects added in this way.
Params:
aspectInstance – the AspectJ aspect instance/**
	 * Add the supplied aspect instance to the chain. The type of the aspect instance
	 * supplied must be a singleton aspect. True singleton lifecycle is not honoured when
	 * using this method - the caller is responsible for managing the lifecycle of any
	 * aspects added in this way.
	 * @param aspectInstance the AspectJ aspect instance
	 */
	public void addAspect(Object aspectInstance) {
		Class<?> aspectClass = aspectInstance.getClass();
		String aspectName = aspectClass.getName();
		AspectMetadata am = createAspectMetadata(aspectClass, aspectName);
		if (am.getAjType().getPerClause().getKind() != PerClauseKind.SINGLETON) {
			throw new IllegalArgumentException(
					"Aspect class [" + aspectClass.getName() + "] does not define a singleton aspect");
		}
		addAdvisorsFromAspectInstanceFactory(
				new SingletonMetadataAwareAspectInstanceFactory(aspectInstance, aspectName));
	}

	
Add an aspect of the supplied type to the end of the advice chain.
Params:
aspectClass – the AspectJ aspect class/**
	 * Add an aspect of the supplied type to the end of the advice chain.
	 * @param aspectClass the AspectJ aspect class
	 */
	public void addAspect(Class<?> aspectClass) {
		String aspectName = aspectClass.getName();
		AspectMetadata am = createAspectMetadata(aspectClass, aspectName);
		MetadataAwareAspectInstanceFactory instanceFactory = createAspectInstanceFactory(am, aspectClass, aspectName);
		addAdvisorsFromAspectInstanceFactory(instanceFactory);
	}


	
Add all Advisors from the supplied MetadataAwareAspectInstanceFactory to the current chain. Exposes any special purpose Advisors if needed. 
See Also:
AspectJProxyUtils.makeAdvisorChainAspectJCapableIfNecessary(List<Advisor>)/**
	 * Add all {@link Advisor Advisors} from the supplied {@link MetadataAwareAspectInstanceFactory}
	 * to the current chain. Exposes any special purpose {@link Advisor Advisors} if needed.
	 * @see AspectJProxyUtils#makeAdvisorChainAspectJCapableIfNecessary(List)
	 */
	private void addAdvisorsFromAspectInstanceFactory(MetadataAwareAspectInstanceFactory instanceFactory) {
		List<Advisor> advisors = this.aspectFactory.getAdvisors(instanceFactory);
		Class<?> targetClass = getTargetClass();
		Assert.state(targetClass != null, "Unresolvable target class");
		advisors = AopUtils.findAdvisorsThatCanApply(advisors, targetClass);
		AspectJProxyUtils.makeAdvisorChainAspectJCapableIfNecessary(advisors);
		AnnotationAwareOrderComparator.sort(advisors);
		addAdvisors(advisors);
	}

	
Create an AspectMetadata instance for the supplied aspect type. /**
	 * Create an {@link AspectMetadata} instance for the supplied aspect type.
	 */
	private AspectMetadata createAspectMetadata(Class<?> aspectClass, String aspectName) {
		AspectMetadata am = new AspectMetadata(aspectClass, aspectName);
		if (!am.getAjType().isAspect()) {
			throw new IllegalArgumentException("Class [" + aspectClass.getName() + "] is not a valid aspect type");
		}
		return am;
	}

	
Create a MetadataAwareAspectInstanceFactory for the supplied aspect type. If the aspect type has no per clause, then a SingletonMetadataAwareAspectInstanceFactory is returned, otherwise a PrototypeAspectInstanceFactory is returned. /**
	 * Create a {@link MetadataAwareAspectInstanceFactory} for the supplied aspect type. If the aspect type
	 * has no per clause, then a {@link SingletonMetadataAwareAspectInstanceFactory} is returned, otherwise
	 * a {@link PrototypeAspectInstanceFactory} is returned.
	 */
	private MetadataAwareAspectInstanceFactory createAspectInstanceFactory(
			AspectMetadata am, Class<?> aspectClass, String aspectName) {

		MetadataAwareAspectInstanceFactory instanceFactory;
		if (am.getAjType().getPerClause().getKind() == PerClauseKind.SINGLETON) {
			// Create a shared aspect instance.
			Object instance = getSingletonAspectInstance(aspectClass);
			instanceFactory = new SingletonMetadataAwareAspectInstanceFactory(instance, aspectName);
		}
		else {
			// Create a factory for independent aspect instances.
			instanceFactory = new SimpleMetadataAwareAspectInstanceFactory(aspectClass, aspectName);
		}
		return instanceFactory;
	}

	
Get the singleton aspect instance for the supplied aspect type.
An instance is created if one cannot be found in the instance cache.
/**
	 * Get the singleton aspect instance for the supplied aspect type.
	 * An instance is created if one cannot be found in the instance cache.
	 */
	private Object getSingletonAspectInstance(Class<?> aspectClass) {
		return aspectCache.computeIfAbsent(aspectClass,
				clazz -> new SimpleAspectInstanceFactory(clazz).getAspectInstance());
	}


	
Create a new proxy according to the settings in this factory.
Can be called repeatedly. Effect will vary if we've added
or removed interfaces. Can add and remove interceptors.
Uses a default class loader: Usually, the thread context class loader
(if necessary for proxy creation).
Returns:
the new proxy/**
	 * Create a new proxy according to the settings in this factory.
	 * <p>Can be called repeatedly. Effect will vary if we've added
	 * or removed interfaces. Can add and remove interceptors.
	 * <p>Uses a default class loader: Usually, the thread context class loader
	 * (if necessary for proxy creation).
	 * @return the new proxy
	 */
	@SuppressWarnings("unchecked")
	public <T> T getProxy() {
		return (T) createAopProxy().getProxy();
	}

	
Create a new proxy according to the settings in this factory.
Can be called repeatedly. Effect will vary if we've added
or removed interfaces. Can add and remove interceptors.
Uses the given class loader (if necessary for proxy creation).
Params:
classLoader – the class loader to create the proxy with
Returns:
the new proxy/**
	 * Create a new proxy according to the settings in this factory.
	 * <p>Can be called repeatedly. Effect will vary if we've added
	 * or removed interfaces. Can add and remove interceptors.
	 * <p>Uses the given class loader (if necessary for proxy creation).
	 * @param classLoader the class loader to create the proxy with
	 * @return the new proxy
	 */
	@SuppressWarnings("unchecked")
	public <T> T getProxy(ClassLoader classLoader) {
		return (T) createAopProxy().getProxy(classLoader);
	}

}