/*
 * Copyright 2002-2019 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.beans.factory.annotation;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.lang.annotation.Annotation;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanCreationException;
import org.springframework.beans.factory.config.DestructionAwareBeanPostProcessor;
import org.springframework.beans.factory.support.MergedBeanDefinitionPostProcessor;
import org.springframework.beans.factory.support.RootBeanDefinition;
import org.springframework.core.Ordered;
import org.springframework.core.PriorityOrdered;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.lang.Nullable;
import org.springframework.util.ClassUtils;
import org.springframework.util.ReflectionUtils;

BeanPostProcessor implementation that invokes annotated init and destroy methods. Allows for an annotation alternative to Spring's InitializingBean and DisposableBean callback interfaces. 
The actual annotation types that this post-processor checks for can be configured through the "initAnnotationType" and "destroyAnnotationType" properties. Any custom annotation can be used, since there are no required annotation attributes. 
Init and destroy annotations may be applied to methods of any visibility:
public, package-protected, protected, or private. Multiple such methods
may be annotated, but it is recommended to only annotate one single
init method and destroy method, respectively.
Spring's CommonAnnotationBeanPostProcessor supports the JSR-250 PostConstruct and PreDestroy annotations out of the box, as init annotation and destroy annotation, respectively. Furthermore, it also supports the Resource annotation for annotation-driven injection of named beans. 
Author:
Juergen Hoeller
See Also:
setInitAnnotationType
setDestroyAnnotationType
Since:
2.5/**
 * {@link org.springframework.beans.factory.config.BeanPostProcessor} implementation
 * that invokes annotated init and destroy methods. Allows for an annotation
 * alternative to Spring's {@link org.springframework.beans.factory.InitializingBean}
 * and {@link org.springframework.beans.factory.DisposableBean} callback interfaces.
 *
 * <p>The actual annotation types that this post-processor checks for can be
 * configured through the {@link #setInitAnnotationType "initAnnotationType"}
 * and {@link #setDestroyAnnotationType "destroyAnnotationType"} properties.
 * Any custom annotation can be used, since there are no required annotation
 * attributes.
 *
 * <p>Init and destroy annotations may be applied to methods of any visibility:
 * public, package-protected, protected, or private. Multiple such methods
 * may be annotated, but it is recommended to only annotate one single
 * init method and destroy method, respectively.
 *
 * <p>Spring's {@link org.springframework.context.annotation.CommonAnnotationBeanPostProcessor}
 * supports the JSR-250 {@link javax.annotation.PostConstruct} and {@link javax.annotation.PreDestroy}
 * annotations out of the box, as init annotation and destroy annotation, respectively.
 * Furthermore, it also supports the {@link javax.annotation.Resource} annotation
 * for annotation-driven injection of named beans.
 *
 * @author Juergen Hoeller
 * @since 2.5
 * @see #setInitAnnotationType
 * @see #setDestroyAnnotationType
 */
@SuppressWarnings("serial")
public class InitDestroyAnnotationBeanPostProcessor
		implements DestructionAwareBeanPostProcessor, MergedBeanDefinitionPostProcessor, PriorityOrdered, Serializable {

	private final transient LifecycleMetadata emptyLifecycleMetadata =
			new LifecycleMetadata(Object.class, Collections.emptyList(), Collections.emptyList()) {
				@Override
				public void checkConfigMembers(RootBeanDefinition beanDefinition) {
				}
				@Override
				public void invokeInitMethods(Object target, String beanName) {
				}
				@Override
				public void invokeDestroyMethods(Object target, String beanName) {
				}
				@Override
				public boolean hasDestroyMethods() {
					return false;
				}
			};


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

	@Nullable
	private Class<? extends Annotation> initAnnotationType;

	@Nullable
	private Class<? extends Annotation> destroyAnnotationType;

	private int order = Ordered.LOWEST_PRECEDENCE;

	@Nullable
	private final transient Map<Class<?>, LifecycleMetadata> lifecycleMetadataCache = new ConcurrentHashMap<>(256);


	
Specify the init annotation to check for, indicating initialization
methods to call after configuration of a bean.
Any custom annotation can be used, since there are no required annotation attributes. There is no default, although a typical choice is the JSR-250 PostConstruct annotation. /**
	 * Specify the init annotation to check for, indicating initialization
	 * methods to call after configuration of a bean.
	 * <p>Any custom annotation can be used, since there are no required
	 * annotation attributes. There is no default, although a typical choice
	 * is the JSR-250 {@link javax.annotation.PostConstruct} annotation.
	 */
	public void setInitAnnotationType(Class<? extends Annotation> initAnnotationType) {
		this.initAnnotationType = initAnnotationType;
	}

	
Specify the destroy annotation to check for, indicating destruction
methods to call when the context is shutting down.
Any custom annotation can be used, since there are no required annotation attributes. There is no default, although a typical choice is the JSR-250 PreDestroy annotation. /**
	 * Specify the destroy annotation to check for, indicating destruction
	 * methods to call when the context is shutting down.
	 * <p>Any custom annotation can be used, since there are no required
	 * annotation attributes. There is no default, although a typical choice
	 * is the JSR-250 {@link javax.annotation.PreDestroy} annotation.
	 */
	public void setDestroyAnnotationType(Class<? extends Annotation> destroyAnnotationType) {
		this.destroyAnnotationType = destroyAnnotationType;
	}

	public void setOrder(int order) {
		this.order = order;
	}

	@Override
	public int getOrder() {
		return this.order;
	}


	@Override
	public void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName) {
		LifecycleMetadata metadata = findLifecycleMetadata(beanType);
		metadata.checkConfigMembers(beanDefinition);
	}

	@Override
	public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
		LifecycleMetadata metadata = findLifecycleMetadata(bean.getClass());
		try {
			metadata.invokeInitMethods(bean, beanName);
		}
		catch (InvocationTargetException ex) {
			throw new BeanCreationException(beanName, "Invocation of init method failed", ex.getTargetException());
		}
		catch (Throwable ex) {
			throw new BeanCreationException(beanName, "Failed to invoke init method", ex);
		}
		return bean;
	}

	@Override
	public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
		return bean;
	}

	@Override
	public void postProcessBeforeDestruction(Object bean, String beanName) throws BeansException {
		LifecycleMetadata metadata = findLifecycleMetadata(bean.getClass());
		try {
			metadata.invokeDestroyMethods(bean, beanName);
		}
		catch (InvocationTargetException ex) {
			String msg = "Destroy method on bean with name '" + beanName + "' threw an exception";
			if (logger.isDebugEnabled()) {
				logger.warn(msg, ex.getTargetException());
			}
			else {
				logger.warn(msg + ": " + ex.getTargetException());
			}
		}
		catch (Throwable ex) {
			logger.warn("Failed to invoke destroy method on bean with name '" + beanName + "'", ex);
		}
	}

	@Override
	public boolean requiresDestruction(Object bean) {
		return findLifecycleMetadata(bean.getClass()).hasDestroyMethods();
	}


	private LifecycleMetadata findLifecycleMetadata(Class<?> clazz) {
		if (this.lifecycleMetadataCache == null) {
			// Happens after deserialization, during destruction...
			return buildLifecycleMetadata(clazz);
		}
		// Quick check on the concurrent map first, with minimal locking.
		LifecycleMetadata metadata = this.lifecycleMetadataCache.get(clazz);
		if (metadata == null) {
			synchronized (this.lifecycleMetadataCache) {
				metadata = this.lifecycleMetadataCache.get(clazz);
				if (metadata == null) {
					metadata = buildLifecycleMetadata(clazz);
					this.lifecycleMetadataCache.put(clazz, metadata);
				}
				return metadata;
			}
		}
		return metadata;
	}

	private LifecycleMetadata buildLifecycleMetadata(final Class<?> clazz) {
		if (!AnnotationUtils.isCandidateClass(clazz, Arrays.asList(this.initAnnotationType, this.destroyAnnotationType))) {
			return this.emptyLifecycleMetadata;
		}

		List<LifecycleElement> initMethods = new ArrayList<>();
		List<LifecycleElement> destroyMethods = new ArrayList<>();
		Class<?> targetClass = clazz;

		do {
			final List<LifecycleElement> currInitMethods = new ArrayList<>();
			final List<LifecycleElement> currDestroyMethods = new ArrayList<>();

			ReflectionUtils.doWithLocalMethods(targetClass, method -> {
				if (this.initAnnotationType != null && method.isAnnotationPresent(this.initAnnotationType)) {
					LifecycleElement element = new LifecycleElement(method);
					currInitMethods.add(element);
					if (logger.isTraceEnabled()) {
						logger.trace("Found init method on class [" + clazz.getName() + "]: " + method);
					}
				}
				if (this.destroyAnnotationType != null && method.isAnnotationPresent(this.destroyAnnotationType)) {
					currDestroyMethods.add(new LifecycleElement(method));
					if (logger.isTraceEnabled()) {
						logger.trace("Found destroy method on class [" + clazz.getName() + "]: " + method);
					}
				}
			});

			initMethods.addAll(0, currInitMethods);
			destroyMethods.addAll(currDestroyMethods);
			targetClass = targetClass.getSuperclass();
		}
		while (targetClass != null && targetClass != Object.class);

		return (initMethods.isEmpty() && destroyMethods.isEmpty() ? this.emptyLifecycleMetadata :
				new LifecycleMetadata(clazz, initMethods, destroyMethods));
	}


	//---------------------------------------------------------------------
	// 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.logger = LogFactory.getLog(getClass());
	}


	
Class representing information about annotated init and destroy methods.
/**
	 * Class representing information about annotated init and destroy methods.
	 */
	private class LifecycleMetadata {

		private final Class<?> targetClass;

		private final Collection<LifecycleElement> initMethods;

		private final Collection<LifecycleElement> destroyMethods;

		@Nullable
		private volatile Set<LifecycleElement> checkedInitMethods;

		@Nullable
		private volatile Set<LifecycleElement> checkedDestroyMethods;

		public LifecycleMetadata(Class<?> targetClass, Collection<LifecycleElement> initMethods,
				Collection<LifecycleElement> destroyMethods) {

			this.targetClass = targetClass;
			this.initMethods = initMethods;
			this.destroyMethods = destroyMethods;
		}

		public void checkConfigMembers(RootBeanDefinition beanDefinition) {
			Set<LifecycleElement> checkedInitMethods = new LinkedHashSet<>(this.initMethods.size());
			for (LifecycleElement element : this.initMethods) {
				String methodIdentifier = element.getIdentifier();
				if (!beanDefinition.isExternallyManagedInitMethod(methodIdentifier)) {
					beanDefinition.registerExternallyManagedInitMethod(methodIdentifier);
					checkedInitMethods.add(element);
					if (logger.isTraceEnabled()) {
						logger.trace("Registered init method on class [" + this.targetClass.getName() + "]: " + element);
					}
				}
			}
			Set<LifecycleElement> checkedDestroyMethods = new LinkedHashSet<>(this.destroyMethods.size());
			for (LifecycleElement element : this.destroyMethods) {
				String methodIdentifier = element.getIdentifier();
				if (!beanDefinition.isExternallyManagedDestroyMethod(methodIdentifier)) {
					beanDefinition.registerExternallyManagedDestroyMethod(methodIdentifier);
					checkedDestroyMethods.add(element);
					if (logger.isTraceEnabled()) {
						logger.trace("Registered destroy method on class [" + this.targetClass.getName() + "]: " + element);
					}
				}
			}
			this.checkedInitMethods = checkedInitMethods;
			this.checkedDestroyMethods = checkedDestroyMethods;
		}

		public void invokeInitMethods(Object target, String beanName) throws Throwable {
			Collection<LifecycleElement> checkedInitMethods = this.checkedInitMethods;
			Collection<LifecycleElement> initMethodsToIterate =
					(checkedInitMethods != null ? checkedInitMethods : this.initMethods);
			if (!initMethodsToIterate.isEmpty()) {
				for (LifecycleElement element : initMethodsToIterate) {
					if (logger.isTraceEnabled()) {
						logger.trace("Invoking init method on bean '" + beanName + "': " + element.getMethod());
					}
					element.invoke(target);
				}
			}
		}

		public void invokeDestroyMethods(Object target, String beanName) throws Throwable {
			Collection<LifecycleElement> checkedDestroyMethods = this.checkedDestroyMethods;
			Collection<LifecycleElement> destroyMethodsToUse =
					(checkedDestroyMethods != null ? checkedDestroyMethods : this.destroyMethods);
			if (!destroyMethodsToUse.isEmpty()) {
				for (LifecycleElement element : destroyMethodsToUse) {
					if (logger.isTraceEnabled()) {
						logger.trace("Invoking destroy method on bean '" + beanName + "': " + element.getMethod());
					}
					element.invoke(target);
				}
			}
		}

		public boolean hasDestroyMethods() {
			Collection<LifecycleElement> checkedDestroyMethods = this.checkedDestroyMethods;
			Collection<LifecycleElement> destroyMethodsToUse =
					(checkedDestroyMethods != null ? checkedDestroyMethods : this.destroyMethods);
			return !destroyMethodsToUse.isEmpty();
		}
	}


	
Class representing injection information about an annotated method.
/**
	 * Class representing injection information about an annotated method.
	 */
	private static class LifecycleElement {

		private final Method method;

		private final String identifier;

		public LifecycleElement(Method method) {
			if (method.getParameterCount() != 0) {
				throw new IllegalStateException("Lifecycle method annotation requires a no-arg method: " + method);
			}
			this.method = method;
			this.identifier = (Modifier.isPrivate(method.getModifiers()) ?
					ClassUtils.getQualifiedMethodName(method) : method.getName());
		}

		public Method getMethod() {
			return this.method;
		}

		public String getIdentifier() {
			return this.identifier;
		}

		public void invoke(Object target) throws Throwable {
			ReflectionUtils.makeAccessible(this.method);
			this.method.invoke(target, (Object[]) null);
		}

		@Override
		public boolean equals(@Nullable Object other) {
			if (this == other) {
				return true;
			}
			if (!(other instanceof LifecycleElement)) {
				return false;
			}
			LifecycleElement otherElement = (LifecycleElement) other;
			return (this.identifier.equals(otherElement.identifier));
		}

		@Override
		public int hashCode() {
			return this.identifier.hashCode();
		}
	}

}