/*
 * 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 java.io.IOException;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.hibernate.FlushMode;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;

import org.springframework.dao.DataAccessResourceFailureException;
import org.springframework.orm.hibernate5.SessionFactoryUtils;
import org.springframework.orm.hibernate5.SessionHolder;
import org.springframework.transaction.support.TransactionSynchronizationManager;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.request.async.CallableProcessingInterceptor;
import org.springframework.web.context.request.async.WebAsyncManager;
import org.springframework.web.context.request.async.WebAsyncUtils;
import org.springframework.web.context.support.WebApplicationContextUtils;
import org.springframework.web.filter.OncePerRequestFilter;

Servlet Filter that binds a Hibernate Session to the thread for the entire
processing of the request. Intended for the "Open Session in View" pattern,
i.e. to allow for lazy loading in web views despite the original transactions
already being completed.
This filter 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). 
NOTE: This filter will by default not flush the Hibernate Session, with the flush mode set to FlushMode.NEVER. It assumes to be used in combination with service layer transactions that care for the flushing: The active transaction manager will temporarily change the flush mode to FlushMode.AUTO during a read-write transaction, with the flush mode reset to FlushMode.NEVER at the end of each transaction. 
WARNING: Applying this filter 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.
Looks up the SessionFactory in Spring's root web application context. Supports a "sessionFactoryBeanName" filter init-param in web.xml; the default bean name is "sessionFactory". 
Author:
Juergen Hoeller
See Also:
lookupSessionFactory
OpenSessionInViewInterceptor
OpenSessionInterceptor
HibernateTransactionManager
TransactionSynchronizationManager
SessionFactory.getCurrentSession()
Since:
4.2/**
 * Servlet Filter that binds a Hibernate Session to the thread for the entire
 * processing of the request. Intended for the "Open Session in View" pattern,
 * i.e. to allow for lazy loading in web views despite the original transactions
 * already being completed.
 *
 * <p>This filter 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><b>NOTE</b>: This filter will by default <i>not</i> flush the Hibernate Session,
 * with the flush mode set to {@code FlushMode.NEVER}. It assumes to be used
 * in combination with service layer transactions that care for the flushing: The
 * active transaction manager will temporarily change the flush mode to
 * {@code FlushMode.AUTO} during a read-write transaction, with the flush
 * mode reset to {@code FlushMode.NEVER} at the end of each transaction.
 *
 * <p><b>WARNING:</b> Applying this filter 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.
 *
 * <p>Looks up the SessionFactory in Spring's root web application context.
 * Supports a "sessionFactoryBeanName" filter init-param in {@code web.xml};
 * the default bean name is "sessionFactory".
 *
 * @author Juergen Hoeller
 * @since 4.2
 * @see #lookupSessionFactory
 * @see OpenSessionInViewInterceptor
 * @see OpenSessionInterceptor
 * @see org.springframework.orm.hibernate5.HibernateTransactionManager
 * @see TransactionSynchronizationManager
 * @see SessionFactory#getCurrentSession()
 */
public class OpenSessionInViewFilter extends OncePerRequestFilter {

	
The default bean name used for the session factory.
/**
	 * The default bean name used for the session factory.
	 */
	public static final String DEFAULT_SESSION_FACTORY_BEAN_NAME = "sessionFactory";

	private String sessionFactoryBeanName = DEFAULT_SESSION_FACTORY_BEAN_NAME;


	
Set the bean name of the SessionFactory to fetch from Spring's
root application context. Default is "sessionFactory".
See Also:
DEFAULT_SESSION_FACTORY_BEAN_NAME/**
	 * Set the bean name of the SessionFactory to fetch from Spring's
	 * root application context. Default is "sessionFactory".
	 * @see #DEFAULT_SESSION_FACTORY_BEAN_NAME
	 */
	public void setSessionFactoryBeanName(String sessionFactoryBeanName) {
		this.sessionFactoryBeanName = sessionFactoryBeanName;
	}

	
Return the bean name of the SessionFactory to fetch from Spring's
root application context.
/**
	 * Return the bean name of the SessionFactory to fetch from Spring's
	 * root application context.
	 */
	protected String getSessionFactoryBeanName() {
		return this.sessionFactoryBeanName;
	}


	
Returns "false" so that the filter may re-bind the opened Hibernate Session to each asynchronously dispatched thread and postpone closing it until the very last asynchronous dispatch. /**
	 * Returns "false" so that the filter may re-bind the opened Hibernate
	 * {@code Session} to each asynchronously dispatched thread and postpone
	 * closing it until the very last asynchronous dispatch.
	 */
	@Override
	protected boolean shouldNotFilterAsyncDispatch() {
		return false;
	}

	
Returns "false" so that the filter may provide a Hibernate Session to each error dispatches. /**
	 * Returns "false" so that the filter may provide a Hibernate
	 * {@code Session} to each error dispatches.
	 */
	@Override
	protected boolean shouldNotFilterErrorDispatch() {
		return false;
	}

	@Override
	protected void doFilterInternal(
			HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
			throws ServletException, IOException {

		SessionFactory sessionFactory = lookupSessionFactory(request);
		boolean participate = false;

		WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
		String key = getAlreadyFilteredAttributeName();

		if (TransactionSynchronizationManager.hasResource(sessionFactory)) {
			// Do not modify the Session: just set the participate flag.
			participate = true;
		}
		else {
			boolean isFirstRequest = !isAsyncDispatch(request);
			if (isFirstRequest || !applySessionBindingInterceptor(asyncManager, key)) {
				logger.debug("Opening Hibernate Session in OpenSessionInViewFilter");
				Session session = openSession(sessionFactory);
				SessionHolder sessionHolder = new SessionHolder(session);
				TransactionSynchronizationManager.bindResource(sessionFactory, sessionHolder);

				AsyncRequestInterceptor interceptor = new AsyncRequestInterceptor(sessionFactory, sessionHolder);
				asyncManager.registerCallableInterceptor(key, interceptor);
				asyncManager.registerDeferredResultInterceptor(key, interceptor);
			}
		}

		try {
			filterChain.doFilter(request, response);
		}

		finally {
			if (!participate) {
				SessionHolder sessionHolder =
						(SessionHolder) TransactionSynchronizationManager.unbindResource(sessionFactory);
				if (!isAsyncStarted(request)) {
					logger.debug("Closing Hibernate Session in OpenSessionInViewFilter");
					SessionFactoryUtils.closeSession(sessionHolder.getSession());
				}
			}
		}
	}

	
Look up the SessionFactory that this filter should use,
taking the current HTTP request as argument.
The default implementation delegates to the lookupSessionFactory() variant without arguments. 
Params:
request – the current request
Returns:
the SessionFactory to use/**
	 * Look up the SessionFactory that this filter should use,
	 * taking the current HTTP request as argument.
	 * <p>The default implementation delegates to the {@link #lookupSessionFactory()}
	 * variant without arguments.
	 * @param request the current request
	 * @return the SessionFactory to use
	 */
	protected SessionFactory lookupSessionFactory(HttpServletRequest request) {
		return lookupSessionFactory();
	}

	
Look up the SessionFactory that this filter should use.
The default implementation looks for a bean with the specified name
in Spring's root application context.
See Also:
getSessionFactoryBeanName
Returns:
the SessionFactory to use/**
	 * Look up the SessionFactory that this filter should use.
	 * <p>The default implementation looks for a bean with the specified name
	 * in Spring's root application context.
	 * @return the SessionFactory to use
	 * @see #getSessionFactoryBeanName
	 */
	protected SessionFactory lookupSessionFactory() {
		if (logger.isDebugEnabled()) {
			logger.debug("Using SessionFactory '" + getSessionFactoryBeanName() + "' for OpenSessionInViewFilter");
		}
		WebApplicationContext wac = WebApplicationContextUtils.getRequiredWebApplicationContext(getServletContext());
		return wac.getBean(getSessionFactoryBeanName(), SessionFactory.class);
	}

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

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

}