https://github.com/spring-projects/spring-framework: Spring Object/Relational Mapping (Spring IO)
  • Juergen Hoeller 
/*
 * Copyright 2002-2018 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.orm.hibernate5.support;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.FlushMode;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;

import org.springframework.dao.DataAccessException;
import org.springframework.dao.DataAccessResourceFailureException;
import org.springframework.lang.Nullable;
import org.springframework.orm.hibernate5.SessionFactoryUtils;
import org.springframework.orm.hibernate5.SessionHolder;
import org.springframework.transaction.support.TransactionSynchronizationManager;
import org.springframework.ui.ModelMap;
import org.springframework.util.Assert;
import org.springframework.web.context.request.AsyncWebRequestInterceptor;
import org.springframework.web.context.request.WebRequest;
import org.springframework.web.context.request.async.CallableProcessingInterceptor;
import org.springframework.web.context.request.async.WebAsyncManager;
import org.springframework.web.context.request.async.WebAsyncUtils;


Spring web request interceptor that binds a Hibernate Session to the thread for the entire processing of the request. 
This class is a concrete expression of the "Open Session in View" pattern, which
is a pattern that allows for the lazy loading of associations in web views despite
the original transactions already being completed.

This interceptor makes Hibernate Sessions available via the current thread, which will be autodetected by transaction managers. It is suitable for service layer transactions via HibernateTransactionManager as well as for non-transactional execution (if configured appropriately). 
In contrast to OpenSessionInViewFilter, this interceptor is configured in a Spring application context and can thus take advantage of bean wiring. 
WARNING: Applying this interceptor to existing logic can cause issues that have not appeared before, through the use of a single Hibernate Session for the processing of an entire request. In particular, the reassociation of persistent objects with a Hibernate Session has to occur at the very beginning of request processing, to avoid clashes with already loaded instances of the same objects. 
Author:Juergen Hoeller
See Also:
Since:4.2
/**
 * Spring web request interceptor that binds a Hibernate {@code Session} to the
 * thread for the entire processing of the request.
 *
 * <p>This class is a concrete expression of the "Open Session in View" pattern, which
 * is a pattern that allows for the lazy loading of associations in web views despite
 * the original transactions already being completed.
 *
 * <p>This interceptor makes Hibernate Sessions available via the current thread,
 * which will be autodetected by transaction managers. It is suitable for service layer
 * transactions via {@link org.springframework.orm.hibernate5.HibernateTransactionManager}
 * as well as for non-transactional execution (if configured appropriately).
 *
 * <p>In contrast to {@link OpenSessionInViewFilter}, this interceptor is configured
 * in a Spring application context and can thus take advantage of bean wiring.
 *
 * <p><b>WARNING:</b> Applying this interceptor to existing logic can cause issues
 * that have not appeared before, through the use of a single Hibernate
 * {@code Session} for the processing of an entire request. In particular, the
 * reassociation of persistent objects with a Hibernate {@code Session} has to
 * occur at the very beginning of request processing, to avoid clashes with already
 * loaded instances of the same objects.
 *
 * @author Juergen Hoeller
 * @since 4.2
 * @see OpenSessionInViewFilter
 * @see OpenSessionInterceptor
 * @see org.springframework.orm.hibernate5.HibernateTransactionManager
 * @see TransactionSynchronizationManager
 * @see SessionFactory#getCurrentSession()
 */
public class OpenSessionInViewInterceptor implements AsyncWebRequestInterceptor {

	
Suffix that gets appended to the SessionFactory toString() representation for the "participate in existing session handling" request attribute. 
See Also:
/**
	 * Suffix that gets appended to the {@code SessionFactory}
	 * {@code toString()} representation for the "participate in existing
	 * session handling" request attribute.
	 * @see #getParticipateAttributeName
	 */
	public static final String PARTICIPATE_SUFFIX = ".PARTICIPATE";

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

	@Nullable
	private SessionFactory sessionFactory;


	
Set the Hibernate SessionFactory that should be used to create Hibernate Sessions.

/**
	 * Set the Hibernate SessionFactory that should be used to create Hibernate Sessions.
	 */
	public void setSessionFactory(@Nullable SessionFactory sessionFactory) {
		this.sessionFactory = sessionFactory;
	}

	
Return the Hibernate SessionFactory that should be used to create Hibernate Sessions.

/**
	 * Return the Hibernate SessionFactory that should be used to create Hibernate Sessions.
	 */
	@Nullable
	public SessionFactory getSessionFactory() {
		return this.sessionFactory;
	}

	private SessionFactory obtainSessionFactory() {
		SessionFactory sf = getSessionFactory();
		Assert.state(sf != null, "No SessionFactory set");
		return sf;
	}


	
Open a new Hibernate Session according and bind it to the thread via the TransactionSynchronizationManager. 
/**
	 * Open a new Hibernate {@code Session} according and bind it to the thread via the
	 * {@link TransactionSynchronizationManager}.
	 */
	@Override
	public void preHandle(WebRequest request) throws DataAccessException {
		String key = getParticipateAttributeName();
		WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
		if (asyncManager.hasConcurrentResult() && applySessionBindingInterceptor(asyncManager, key)) {
			return;
		}

		if (TransactionSynchronizationManager.hasResource(obtainSessionFactory())) {
			// Do not modify the Session: just mark the request accordingly.
			Integer count = (Integer) request.getAttribute(key, WebRequest.SCOPE_REQUEST);
			int newCount = (count != null ? count + 1 : 1);
			request.setAttribute(getParticipateAttributeName(), newCount, WebRequest.SCOPE_REQUEST);
		}
		else {
			logger.debug("Opening Hibernate Session in OpenSessionInViewInterceptor");
			Session session = openSession();
			SessionHolder sessionHolder = new SessionHolder(session);
			TransactionSynchronizationManager.bindResource(obtainSessionFactory(), sessionHolder);

			AsyncRequestInterceptor asyncRequestInterceptor =
					new AsyncRequestInterceptor(obtainSessionFactory(), sessionHolder);
			asyncManager.registerCallableInterceptor(key, asyncRequestInterceptor);
			asyncManager.registerDeferredResultInterceptor(key, asyncRequestInterceptor);
		}
	}

	@Override
	public void postHandle(WebRequest request, @Nullable ModelMap model) {
	}

	
Unbind the Hibernate Session from the thread and close it). 
See Also:
/**
	 * Unbind the Hibernate {@code Session} from the thread and close it).
	 * @see TransactionSynchronizationManager
	 */
	@Override
	public void afterCompletion(WebRequest request, @Nullable Exception ex) throws DataAccessException {
		if (!decrementParticipateCount(request)) {
			SessionHolder sessionHolder =
					(SessionHolder) TransactionSynchronizationManager.unbindResource(obtainSessionFactory());
			logger.debug("Closing Hibernate Session in OpenSessionInViewInterceptor");
			SessionFactoryUtils.closeSession(sessionHolder.getSession());
		}
	}

	private boolean decrementParticipateCount(WebRequest request) {
		String participateAttributeName = getParticipateAttributeName();
		Integer count = (Integer) request.getAttribute(participateAttributeName, WebRequest.SCOPE_REQUEST);
		if (count == null) {
			return false;
		}
		// Do not modify the Session: just clear the marker.
		if (count > 1) {
			request.setAttribute(participateAttributeName, count - 1, WebRequest.SCOPE_REQUEST);
		}
		else {
			request.removeAttribute(participateAttributeName, WebRequest.SCOPE_REQUEST);
		}
		return true;
	}

	@Override
	public void afterConcurrentHandlingStarted(WebRequest request) {
		if (!decrementParticipateCount(request)) {
			TransactionSynchronizationManager.unbindResource(obtainSessionFactory());
		}
	}

	
Open a Session for the SessionFactory that this interceptor uses.

The default implementation delegates to the SessionFactory.openSession method and sets the Session's flush mode to "MANUAL". 
Throws:
See Also:
Returns:the Session to use
/**
	 * Open a Session for the SessionFactory that this interceptor uses.
	 * <p>The default implementation delegates to the {@link SessionFactory#openSession}
	 * method and sets the {@link Session}'s flush mode to "MANUAL".
	 * @return the Session to use
	 * @throws DataAccessResourceFailureException if the Session could not be created
	 * @see FlushMode#MANUAL
	 */
	@SuppressWarnings("deprecation")
	protected Session openSession() throws DataAccessResourceFailureException {
		try {
			Session session = obtainSessionFactory().openSession();
			session.setFlushMode(FlushMode.MANUAL);
			return session;
		}
		catch (HibernateException ex) {
			throw new DataAccessResourceFailureException("Could not open Hibernate Session", ex);
		}
	}

	
Return the name of the request attribute that identifies that a request is
already intercepted.

The default implementation takes the toString() representation of the SessionFactory instance and appends PARTICIPATE_SUFFIX. 
/**
	 * Return the name of the request attribute that identifies that a request is
	 * already intercepted.
	 * <p>The default implementation takes the {@code toString()} representation
	 * of the {@code SessionFactory} instance and appends {@link #PARTICIPATE_SUFFIX}.
	 */
	protected String getParticipateAttributeName() {
		return obtainSessionFactory().toString() + PARTICIPATE_SUFFIX;
	}

	private boolean applySessionBindingInterceptor(WebAsyncManager asyncManager, String key) {
		CallableProcessingInterceptor cpi = asyncManager.getCallableInterceptor(key);
		if (cpi == null) {
			return false;
		}
		((AsyncRequestInterceptor) cpi).bindSession();
		return true;
	}

}