/*
* Copyright 2002-2008 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.hibernate3.support;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.springframework.dao.DataAccessException;
import org.springframework.orm.hibernate3.HibernateAccessor;
import org.springframework.orm.hibernate3.SessionFactoryUtils;
import org.springframework.orm.hibernate3.SessionHolder;
import org.springframework.transaction.support.TransactionSynchronizationManager;
import org.springframework.ui.ModelMap;
import org.springframework.web.context.request.WebRequest;
import org.springframework.web.context.request.WebRequestInterceptor;
/**
* Spring web request interceptor that binds a Hibernate <code>Session</code> 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 <code>Sessions</code> available via the current
* thread, which will be autodetected by transaction managers. It is suitable for
* service layer transactions via
* {@link org.springframework.orm.hibernate3.HibernateTransactionManager} or
* {@link org.springframework.transaction.jta.JtaTransactionManager} as well as for
* non-transactional execution (if configured appropriately).
*
* <p><b>NOTE</b>: This interceptor will by default <i>not</i> flush the Hibernate
* <code>Session</code>, with the flush mode being set to <code>FlushMode.NEVER</code>.
* It assumes that it will be used in combination with service layer transactions
* that handle the flushing: the active transaction manager will temporarily change
* the flush mode to <code>FlushMode.AUTO</code> during a read-write transaction,
* with the flush mode reset to <code>FlushMode.NEVER</code> at the end of each
* transaction. If you intend to use this interceptor without transactions, consider
* changing the default flush mode (through the
* {@link #setFlushMode(int) "flushMode"} property).
*
* <p>In contrast to {@link OpenSessionInViewFilter}, this interceptor is
* configured in a Spring application context and can thus take advantage of bean
* wiring. It inherits common Hibernate configuration properties from
* {@link org.springframework.orm.hibernate3.HibernateAccessor},
* to be configured in a bean definition.
*
* <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</code> for the processing of an entire request. In particular, the
* reassociation of persistent objects with a Hibernate <code>Session</code> has to
* occur at the very beginning of request processing, to avoid clashes with already
* loaded instances of the same objects.
*
* <p>Alternatively, turn this interceptor into deferred close mode, by specifying
* "singleSession"="false": It will not use a single session per request then,
* but rather let each data access operation or transaction use its own session
* (as would be the case without Open Session in View). Each of those sessions will
* be registered for deferred close though, which will actually be processed at
* request completion.
*
* <p>A single session per request allows for the most efficient first-level caching,
* but can cause side effects, for example on <code>saveOrUpdate</code> or when
* continuing after a rolled-back transaction. The deferred close strategy is as safe
* as no Open Session in View in that respect, while still allowing for lazy loading
* in views (but not providing a first-level cache for the entire request).
*
* @author Juergen Hoeller
* @since 1.2
* @see #setSingleSession
* @see #setFlushMode
* @see OpenSessionInViewFilter
* @see org.springframework.orm.hibernate3.HibernateInterceptor
* @see org.springframework.orm.hibernate3.HibernateTransactionManager
* @see org.springframework.orm.hibernate3.SessionFactoryUtils#getSession
* @see org.springframework.transaction.support.TransactionSynchronizationManager
*/
public class OpenSessionInViewInterceptor extends HibernateAccessor implements WebRequestInterceptor {
/**
* Suffix that gets appended to the <code>SessionFactory</code>
* <code>toString()</code> representation for the "participate in existing
* session handling" request attribute.
* @see #getParticipateAttributeName
*/
public static final String PARTICIPATE_SUFFIX = ".PARTICIPATE";
private boolean singleSession = true;
/**
* Create a new <code>OpenSessionInViewInterceptor</code>,
* turning the default flushMode to <code>FLUSH_NEVER</code>.
* @see #setFlushMode
*/
public OpenSessionInViewInterceptor() {
setFlushMode(FLUSH_NEVER);
}
/**
* Set whether to use a single session for each request. Default is "true".
* <p>If set to false, each data access operation or transaction will use
* its own session (like without Open Session in View). Each of those
* sessions will be registered for deferred close, though, actually
* processed at request completion.
* @see SessionFactoryUtils#initDeferredClose
* @see SessionFactoryUtils#processDeferredClose
*/
public void setSingleSession(boolean singleSession) {
this.singleSession = singleSession;
}
/**
* Return whether to use a single session for each request.
*/
protected boolean isSingleSession() {
return singleSession;
}
/**
* Open a new Hibernate <code>Session</code> according to the settings of this
* <code>HibernateAccessor</code> and bind it to the thread via the
* {@link TransactionSynchronizationManager}.
* @see org.springframework.orm.hibernate3.SessionFactoryUtils#getSession
*/
public void preHandle(WebRequest request) throws DataAccessException {
if ((isSingleSession() && TransactionSynchronizationManager.hasResource(getSessionFactory())) ||
SessionFactoryUtils.isDeferredCloseActive(getSessionFactory())) {
// Do not modify the Session: just mark the request accordingly.
String participateAttributeName = getParticipateAttributeName();
Integer count = (Integer) request.getAttribute(participateAttributeName, WebRequest.SCOPE_REQUEST);
int newCount = (count != null ? count + 1 : 1);
request.setAttribute(getParticipateAttributeName(), newCount, WebRequest.SCOPE_REQUEST);
}
else {
if (isSingleSession()) {
// single session mode
logger.debug("Opening single Hibernate Session in OpenSessionInViewInterceptor");
Session session = SessionFactoryUtils.getSession(
getSessionFactory(), getEntityInterceptor(), getJdbcExceptionTranslator());
applyFlushMode(session, false);
TransactionSynchronizationManager.bindResource(getSessionFactory(), new SessionHolder(session));
}
else {
// deferred close mode
SessionFactoryUtils.initDeferredClose(getSessionFactory());
}
}
}
/**
* Flush the Hibernate <code>Session</code> before view rendering, if necessary.
* <p>Note that this just applies in {@link #isSingleSession() single session mode}!
* <p>The default is <code>FLUSH_NEVER</code> to avoid this extra flushing,
* assuming that service layer transactions have flushed their changes on commit.
* @see #setFlushMode
*/
public void postHandle(WebRequest request, ModelMap model) throws DataAccessException {
if (isSingleSession()) {
// Only potentially flush in single session mode.
SessionHolder sessionHolder =
(SessionHolder) TransactionSynchronizationManager.getResource(getSessionFactory());
logger.debug("Flushing single Hibernate Session in OpenSessionInViewInterceptor");
try {
flushIfNecessary(sessionHolder.getSession(), false);
}
catch (HibernateException ex) {
throw convertHibernateAccessException(ex);
}
}
}
/**
* Unbind the Hibernate <code>Session</code> from the thread and close it (in
* single session mode), or process deferred close for all sessions that have
* been opened during the current request (in deferred close mode).
* @see org.springframework.transaction.support.TransactionSynchronizationManager
*/
public void afterCompletion(WebRequest request, Exception ex) throws DataAccessException {
String participateAttributeName = getParticipateAttributeName();
Integer count = (Integer) request.getAttribute(participateAttributeName, WebRequest.SCOPE_REQUEST);
if (count != null) {
// 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);
}
}
else {
if (isSingleSession()) {
// single session mode
SessionHolder sessionHolder =
(SessionHolder) TransactionSynchronizationManager.unbindResource(getSessionFactory());
logger.debug("Closing single Hibernate Session in OpenSessionInViewInterceptor");
SessionFactoryUtils.closeSession(sessionHolder.getSession());
}
else {
// deferred close mode
SessionFactoryUtils.processDeferredClose(getSessionFactory());
}
}
}
/**
* Return the name of the request attribute that identifies that a request is
* already intercepted.
* <p>The default implementation takes the <code>toString()</code> representation
* of the <code>SessionFactory</code> instance and appends {@link #PARTICIPATE_SUFFIX}.
*/
protected String getParticipateAttributeName() {
return getSessionFactory().toString() + PARTICIPATE_SUFFIX;
}
}
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