/*
 * Copyright 2002-2007 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.interceptor;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Properties;

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

import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.TransactionStatus;
import org.springframework.transaction.support.CallbackPreferringPlatformTransactionManager;
import org.springframework.transaction.support.TransactionCallback;

/**
 * AOP Alliance MethodInterceptor for declarative transaction
 * management using the common Spring transaction infrastructure
 * ({@link org.springframework.transaction.PlatformTransactionManager}).
 *
 * <p>Derives from the {@link TransactionAspectSupport} class which
 * contains the integration with Spring's underlying transaction API.
 * TransactionInterceptor simply calls the relevant superclass methods
 * such as {@link #createTransactionIfNecessary} in the correct order.
 *
 * <p>TransactionInterceptors are thread-safe.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see TransactionProxyFactoryBean
 * @see org.springframework.aop.framework.ProxyFactoryBean
 * @see org.springframework.aop.framework.ProxyFactory
 */
public class TransactionInterceptor extends TransactionAspectSupport implements MethodInterceptor, Serializable {

	/**
	 * Create a new TransactionInterceptor.
	 * <p>Transaction manager and transaction attributes still need to be set.
	 * @see #setTransactionManager
	 * @see #setTransactionAttributes(java.util.Properties)
	 * @see #setTransactionAttributeSource(TransactionAttributeSource)
	 */
	public TransactionInterceptor() {
	}

	/**
	 * Create a new TransactionInterceptor.
	 * @param ptm the transaction manager to perform the actual transaction management
	 * @param attributes the transaction attributes in properties format
	 * @see #setTransactionManager
	 * @see #setTransactionAttributes(java.util.Properties)
	 */
	public TransactionInterceptor(PlatformTransactionManager ptm, Properties attributes) {
		setTransactionManager(ptm);
		setTransactionAttributes(attributes);
	}

	/**
	 * Create a new TransactionInterceptor.
	 * @param ptm the transaction manager to perform the actual transaction management
	 * @param tas the attribute source to be used to find transaction attributes
	 * @see #setTransactionManager
	 * @see #setTransactionAttributeSource(TransactionAttributeSource)
	 */
	public TransactionInterceptor(PlatformTransactionManager ptm, TransactionAttributeSource tas) {
		setTransactionManager(ptm);
		setTransactionAttributeSource(tas);
	}


	public Object invoke(final MethodInvocation invocation) throws Throwable {
		// Work out the target class: may be <code>null</code>.
		// The TransactionAttributeSource should be passed the target class
		// as well as the method, which may be from an interface.
		Class targetClass = (invocation.getThis() != null ? invocation.getThis().getClass() : null);

		// If the transaction attribute is null, the method is non-transactional.
		final TransactionAttribute txAttr =
				getTransactionAttributeSource().getTransactionAttribute(invocation.getMethod(), targetClass);
		final String joinpointIdentification = methodIdentification(invocation.getMethod());

		if (txAttr == null || !(getTransactionManager() instanceof CallbackPreferringPlatformTransactionManager)) {
			// Standard transaction demarcation with getTransaction and commit/rollback calls.
			TransactionInfo txInfo = createTransactionIfNecessary(txAttr, joinpointIdentification);
			Object retVal = null;
			try {
				// This is an around advice: Invoke the next interceptor in the chain.
				// This will normally result in a target object being invoked.
				retVal = invocation.proceed();
			}
			catch (Throwable ex) {
				// target invocation exception
				completeTransactionAfterThrowing(txInfo, ex);
				throw ex;
			}
			finally {
				cleanupTransactionInfo(txInfo);
			}
			commitTransactionAfterReturning(txInfo);
			return retVal;
		}

		else {
			// It's a CallbackPreferringPlatformTransactionManager: pass a TransactionCallback in.
			try {
				Object result = ((CallbackPreferringPlatformTransactionManager) getTransactionManager()).execute(txAttr,
						new TransactionCallback() {
							public Object doInTransaction(TransactionStatus status) {
								TransactionInfo txInfo = prepareTransactionInfo(txAttr, joinpointIdentification, status);
								try {
									return invocation.proceed();
								}
								catch (Throwable ex) {
									if (txAttr.rollbackOn(ex)) {
										// A RuntimeException: will lead to a rollback.
										if (ex instanceof RuntimeException) {
											throw (RuntimeException) ex;
										}
										else {
											throw new ThrowableHolderException(ex);
										}
									}
									else {
										// A normal return value: will lead to a commit.
										return new ThrowableHolder(ex);
									}
								}
								finally {
									cleanupTransactionInfo(txInfo);
								}
							}
						});

				// Check result: It might indicate a Throwable to rethrow.
				if (result instanceof ThrowableHolder) {
					throw ((ThrowableHolder) result).getThrowable();
				}
				else {
					return result;
				}
			}
			catch (ThrowableHolderException ex) {
				throw ex.getCause();
			}
		}
	}


	//---------------------------------------------------------------------
	// Serialization support
	//---------------------------------------------------------------------

	private void readObject(ObjectInputStream ois) throws IOException, ClassNotFoundException {
		// Rely on default serialization, although this class itself doesn't carry state anyway...
		ois.defaultReadObject();

		// Serialize all relevant superclass fields.
		// Superclass can't implement Serializable because it also serves as base class
		// for AspectJ aspects (which are not allowed to implement Serializable)!
		setTransactionManager((PlatformTransactionManager) ois.readObject());
		setTransactionAttributeSource((TransactionAttributeSource) ois.readObject());
	}

	private void writeObject(ObjectOutputStream oos) throws IOException {
		// Rely on default serialization, although this class itself doesn't carry state anyway...
		oos.defaultWriteObject();

		// Deserialize superclass fields.
		oos.writeObject(getTransactionManager());
		oos.writeObject(getTransactionAttributeSource());
	}


	/**
	 * Internal holder class for a Throwable, used as a return value
	 * from a TransactionCallback (to be subsequently unwrapped again).
	 */
	private static class ThrowableHolder {

		private final Throwable throwable;

		public ThrowableHolder(Throwable throwable) {
			this.throwable = throwable;
		}

		public final Throwable getThrowable() {
			return this.throwable;
		}
	}


	/**
	 * Internal holder class for a Throwable, used as a RuntimeException to be
	 * thrown from a TransactionCallback (and subsequently unwrapped again).
	 */
	private static class ThrowableHolderException extends RuntimeException {

		public ThrowableHolderException(Throwable throwable) {
			super(throwable);
		}

		public String toString() {
			return getCause().toString();
		}
	}

}
