/*
 * Copyright 2002-2017 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.transaction.event;

import java.lang.reflect.Method;

import org.springframework.context.ApplicationEvent;
import org.springframework.context.event.ApplicationListenerMethodAdapter;
import org.springframework.context.event.EventListener;
import org.springframework.context.event.GenericApplicationListener;
import org.springframework.core.annotation.AnnotatedElementUtils;
import org.springframework.transaction.support.TransactionSynchronization;
import org.springframework.transaction.support.TransactionSynchronizationAdapter;
import org.springframework.transaction.support.TransactionSynchronizationManager;

GenericApplicationListener adapter that delegates the processing of an event to a TransactionalEventListener annotated method. Supports the exact same features as any regular EventListener annotated method but is aware of the transactional context of the event publisher. 
Processing of TransactionalEventListener is enabled automatically when Spring's transaction management is enabled. For other cases, registering a bean of type TransactionalEventListenerFactory is required. 
Author:
Stephane Nicoll, Juergen Hoeller
See Also:
ApplicationListenerMethodAdapter
TransactionalEventListener
Since:
4.2/**
 * {@link GenericApplicationListener} adapter that delegates the processing of
 * an event to a {@link TransactionalEventListener} annotated method. Supports
 * the exact same features as any regular {@link EventListener} annotated method
 * but is aware of the transactional context of the event publisher.
 *
 * <p>Processing of {@link TransactionalEventListener} is enabled automatically
 * when Spring's transaction management is enabled. For other cases, registering
 * a bean of type {@link TransactionalEventListenerFactory} is required.
 *
 * @author Stephane Nicoll
 * @author Juergen Hoeller
 * @since 4.2
 * @see ApplicationListenerMethodAdapter
 * @see TransactionalEventListener
 */
class ApplicationListenerMethodTransactionalAdapter extends ApplicationListenerMethodAdapter {

	private final TransactionalEventListener annotation;


	public ApplicationListenerMethodTransactionalAdapter(String beanName, Class<?> targetClass, Method method) {
		super(beanName, targetClass, method);
		TransactionalEventListener ann = AnnotatedElementUtils.findMergedAnnotation(method, TransactionalEventListener.class);
		if (ann == null) {
			throw new IllegalStateException("No TransactionalEventListener annotation found on method: " + method);
		}
		this.annotation = ann;
	}


	@Override
	public void onApplicationEvent(ApplicationEvent event) {
		if (TransactionSynchronizationManager.isSynchronizationActive()) {
			TransactionSynchronization transactionSynchronization = createTransactionSynchronization(event);
			TransactionSynchronizationManager.registerSynchronization(transactionSynchronization);
		}
		else if (this.annotation.fallbackExecution()) {
			if (this.annotation.phase() == TransactionPhase.AFTER_ROLLBACK && logger.isWarnEnabled()) {
				logger.warn("Processing " + event + " as a fallback execution on AFTER_ROLLBACK phase");
			}
			processEvent(event);
		}
		else {
			// No transactional event execution at all
			if (logger.isDebugEnabled()) {
				logger.debug("No transaction is active - skipping " + event);
			}
		}
	}

	private TransactionSynchronization createTransactionSynchronization(ApplicationEvent event) {
		return new TransactionSynchronizationEventAdapter(this, event, this.annotation.phase());
	}


	private static class TransactionSynchronizationEventAdapter extends TransactionSynchronizationAdapter {

		private final ApplicationListenerMethodAdapter listener;

		private final ApplicationEvent event;

		private final TransactionPhase phase;

		public TransactionSynchronizationEventAdapter(ApplicationListenerMethodAdapter listener,
				ApplicationEvent event, TransactionPhase phase) {

			this.listener = listener;
			this.event = event;
			this.phase = phase;
		}

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

		@Override
		public void beforeCommit(boolean readOnly) {
			if (this.phase == TransactionPhase.BEFORE_COMMIT) {
				processEvent();
			}
		}

		@Override
		public void afterCompletion(int status) {
			if (this.phase == TransactionPhase.AFTER_COMMIT && status == STATUS_COMMITTED) {
				processEvent();
			}
			else if (this.phase == TransactionPhase.AFTER_ROLLBACK && status == STATUS_ROLLED_BACK) {
				processEvent();
			}
			else if (this.phase == TransactionPhase.AFTER_COMPLETION) {
				processEvent();
			}
		}

		protected void processEvent() {
			this.listener.processEvent(this.event);
		}
	}

}