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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.reflect.Method;

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 didWeStartWork = new ThreadLocal<>();

	public GuicedPersistenceTxnInterceptor()
	{
		//No config required
	}

	@Override
	@SuppressWarnings("Duplicates")
	public Object invoke(MethodInvocation methodInvocation) throws Throwable
	{
		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()));

		if (!emProvider.isWorking())
		{
			emProvider.begin();
			didWeStartWork.set(true);
		}
		Boolean startedWork = didWeStartWork.get() == null ? false : didWeStartWork.get();
		EntityManager em = emProvider.get();

		boolean transactionAlreadyStarted = false;
		for (ITransactionHandler handler : GuiceContext.get(ITransactionHandlerReader))
		{
			if (handler.active(unit) && 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)
		{
			if (rollbackIfNecessary(transactional, e, unit, em))
			{
				for (ITransactionHandler handler : GuiceContext.get(ITransactionHandlerReader))
				{
					if (handler.active(unit))
					{
						handler.commitTransacation(false, em, unit);
					}
				}
			}

			if (startedWork)
			{
				didWeStartWork.remove();
				unitOfWork.end();
			}

			throw e;
		}
		try
		{
			for (ITransactionHandler handler : GuiceContext.get(ITransactionHandlerReader))
			{
				if (handler.active(unit))
				{
					handler.commitTransacation(false, em, unit);
				}
			}
		}
		finally
		{
			if (startedWork)
			{
				didWeStartWork.remove();
				unitOfWork.end();
			}
		}
		return result;
	}

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

		transactional = method.getAnnotation(Transactional.class);
		if (null == transactional)
		{
			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
	 */
	@SuppressWarnings("Duplicates")
	private boolean rollbackIfNecessary(Transactional transactional, Exception e, PersistenceUnit unit, EntityManager em)
	{
		boolean commit = true;

		for (Class rollBackOn : transactional.rollbackOn())
		{
			if (rollBackOn.isInstance(e))
			{
				commit = false;

				for (Class exceptOn : transactional.ignore())
				{
					if (exceptOn.isInstance(e))
					{
						commit = true;
						break;
					}
				}

				if (!commit)
				{
					for (ITransactionHandler handler : GuiceContext.get(ITransactionHandlerReader))
					{
						if (handler.active(unit))
						{
							handler.rollbackTransacation(false, em, unit);
						}
					}
				}
				break;
			}
		}

		return commit;
	}
}