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A complete JPA 2.1 implementation for Standalone or EE Implementation. Enables Multiple Persistence units with full JTA Support using BTM. Perfect for Guice implementations, test suites, and Guice enabled Web Applications or EAR Projects. Requires JDK 8
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/*
 * Copyright (C) 2010 Google, Inc.
 *
 * 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 com.jwebmp.guicedpersistence.injectors;

import com.google.inject.Key;
import com.google.inject.persist.UnitOfWork;
import com.jwebmp.guicedinjection.GuiceContext;
import com.jwebmp.guicedpersistence.db.annotations.Transactional;
import com.jwebmp.guicedpersistence.services.ITransactionHandler;
import com.oracle.jaxb21.PersistenceUnit;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;

import javax.persistence.EntityManager;
import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import static com.jwebmp.guicedpersistence.scanners.PersistenceServiceLoadersBinder.*;

/**
 * @author Dhanji R. Prasanna ([email protected])
 */
public class GuicedPersistenceTxnInterceptor
		implements MethodInterceptor
{
	/**
	 * Tracks if the unit of work was begun implicitly by this transaction.
	 */
	private final ThreadLocal, Boolean>> didWeStartWork = new ThreadLocal<>();

	public GuicedPersistenceTxnInterceptor()
	{
		//No config required
	}

	@Override
	public Object invoke(MethodInvocation methodInvocation) throws Throwable
	{
		if (didWeStartWork.get() == null)
		{
			didWeStartWork.set(new ConcurrentHashMap<>(5, 2, 1));
		}

		Transactional transactional = readTransactionMetadata(methodInvocation);

		CustomJpaPersistService emProvider = GuiceContext.get(Key.get(CustomJpaPersistService.class, transactional.entityManagerAnnotation()));
		UnitOfWork unitOfWork = GuiceContext.get(Key.get(UnitOfWork.class, transactional.entityManagerAnnotation()));
		PersistenceUnit unit = GuiceContext.get(Key.get(PersistenceUnit.class, transactional.entityManagerAnnotation()));

		// Should we start a unit of work?
		if (!emProvider.isWorking())
		{
			emProvider.begin();
			Map, Boolean> runningMap = didWeStartWork.get();
			runningMap.put(transactional.entityManagerAnnotation(), true);
		}
		Map, Boolean> mappedOut = didWeStartWork.get();
		Boolean startedWork = mappedOut != null && mappedOut.get(transactional.entityManagerAnnotation()) != null;

		EntityManager em = emProvider.get();

		// Allow 'joining' of transactions if there is an enclosing @Transactional method.
		boolean transactionAlreadyStarted = false;
		for (ITransactionHandler handler : GuiceContext.get(ITransactionHandlerReader))
		{
			if (handler.transactionExists(em, unit))
			{
				transactionAlreadyStarted = true;
				break;
			}
		}

		if (!startedWork && transactionAlreadyStarted)
		{
			return methodInvocation.proceed();
		}


		for (ITransactionHandler handler : GuiceContext.get(ITransactionHandlerReader))
		{
			if (handler.active(unit))
			{
				handler.beginTransacation(false, em, unit);
			}
		}

		Object result;
		try
		{
			result = methodInvocation.proceed();
		}
		catch (Exception e)
		{
			//commit transaction only if rollback didn't occur
			if (rollbackIfNecessary(transactional, e, unit, em))
			{
				for (ITransactionHandler handler : GuiceContext.get(ITransactionHandlerReader))
				{
					if (handler.active(unit))
					{
						handler.commitTransacation(false, em, unit);
					}
				}
			}
			//close the em if necessary
			if (startedWork)
			{
				mappedOut.remove(transactional.entityManagerAnnotation());
				unitOfWork.end();
			}
			//propagate whatever exception is thrown anyway
			throw e;
		}

		//everything was normal so commit the txn (do not move into try block above as it
		//  interferes with the advised method's throwing semantics)
		try
		{
			for (ITransactionHandler handler : GuiceContext.get(ITransactionHandlerReader))
			{
				if (handler.active(unit))
				{
					handler.commitTransacation(false, em, unit);
				}
			}
		}
		finally
		{
			//close the em if necessary
			if (startedWork)
			{
				mappedOut.remove(transactional.entityManagerAnnotation());
				unitOfWork.end();
			}
		}

		//or return result
		return result;
	}

	/**
	 * Method readTransactionMetadata ...
	 *
	 * @param methodInvocation
	 * 		of type MethodInvocation
	 *
	 * @return Transactional
	 */
	private Transactional readTransactionMetadata(MethodInvocation methodInvocation)
	{
		Transactional transactional;
		Method method = methodInvocation.getMethod();
		Class targetClass = methodInvocation.getThis()
		                                       .getClass();

		transactional = method.getAnnotation(Transactional.class);
		if (null == transactional)
		{
			// If none on method, try the class.
			transactional = targetClass.getAnnotation(Transactional.class);
		}
		return transactional;
	}

	/**
	 * Returns True if rollback DID NOT HAPPEN (i.e. if commit should continue).
	 *
	 * @param transactional
	 * 		The metadata annotation of the method
	 * @param e
	 * 		The exception to test for rollback
	 * @param em
	 * 		Entity Manager
	 * @param unit
	 * 		The associated persistence unit
	 */
	private boolean rollbackIfNecessary(Transactional transactional, Exception e, PersistenceUnit unit, EntityManager em)
	{
		boolean commit = true;

		//check rollback clauses
		for (Class rollBackOn : transactional.rollbackOn())
		{

			//if one matched, try to perform a rollback
			if (rollBackOn.isInstance(e))
			{
				commit = false;

				//check ignore clauses (supercedes rollback clause)
				for (Class exceptOn : transactional.ignore())
				{
					//An exception to the rollback clause was found, DON'T rollback
					// (i.e. commit and throw anyway)
					if (exceptOn.isInstance(e))
					{
						commit = true;
						break;
					}
				}

				//rollback only if nothing matched the ignore check
				if (!commit)
				{
					for (ITransactionHandler handler : GuiceContext.get(ITransactionHandlerReader))
					{
						if (handler.active(unit))
						{
							handler.rollbackTransacation(false, em, unit);
						}
					}
				}
				//otherwise continue to commit
				break;
			}
		}

		return commit;
	}
}