Spring Framework example source code file (OpenEntityManagerInViewInterceptor.java)

This example Spring Framework source code file (OpenEntityManagerInViewInterceptor.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Spring Framework tags/keywords

dataaccessexception, entitymanager, entitymanager, entitymanagerholder, integer, integer, jpa, jpa, openentitymanagerinviewinterceptor, opening, participate_suffix, persistenceexception, string, string

The Spring Framework OpenEntityManagerInViewInterceptor.java source code

/*
 * 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.jpa.support;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceException;

import org.springframework.dao.DataAccessException;
import org.springframework.dao.DataAccessResourceFailureException;
import org.springframework.orm.jpa.EntityManagerFactoryAccessor;
import org.springframework.orm.jpa.EntityManagerHolder;
import org.springframework.orm.jpa.EntityManagerFactoryUtils;
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 JPA EntityManager to the
 * thread for the entire processing of the request. Intended for the "Open
 * EntityManager in View" pattern, i.e. to allow for lazy loading in
 * web views despite the original transactions already being completed.
 *
 * <p>This interceptor makes JPA EntityManagers available via the current thread,
 * which will be autodetected by transaction managers. It is suitable for service
 * layer transactions via {@link org.springframework.orm.jpa.JpaTransactionManager}
 * or {@link org.springframework.transaction.jta.JtaTransactionManager} as well
 * as for non-transactional read-only execution.
 *
 * <p>In contrast to {@link OpenEntityManagerInViewFilter}, this interceptor
 * is set up in a Spring application context and can thus take advantage of
 * bean wiring. It inherits common JPA configuration properties from
 * {@link org.springframework.orm.jpa.JpaAccessor}, to be configured in a
 * bean definition.
 *
 * @author Juergen Hoeller
 * @since 2.0
 * @see OpenEntityManagerInViewFilter
 * @see org.springframework.orm.jpa.JpaInterceptor
 * @see org.springframework.orm.jpa.JpaTransactionManager
 * @see org.springframework.orm.jpa.JpaTemplate#execute
 * @see org.springframework.orm.jpa.SharedEntityManagerCreator
 * @see org.springframework.transaction.support.TransactionSynchronizationManager
 */
public class OpenEntityManagerInViewInterceptor extends EntityManagerFactoryAccessor implements WebRequestInterceptor {

	/**
	 * Suffix that gets appended to the EntityManagerFactory toString
	 * representation for the "participate in existing entity manager
	 * handling" request attribute.
	 * @see #getParticipateAttributeName
	 */
	public static final String PARTICIPATE_SUFFIX = ".PARTICIPATE";


	public void preHandle(WebRequest request) throws DataAccessException {
		if (TransactionSynchronizationManager.hasResource(getEntityManagerFactory())) {
			// do not modify the EntityManager: just mark the request accordingly
			String participateAttributeName = getParticipateAttributeName();
			Integer count = (Integer) request.getAttribute(participateAttributeName, WebRequest.SCOPE_REQUEST);
			int newCount = (count != null) ? count.intValue() + 1 : 1;
			request.setAttribute(getParticipateAttributeName(), new Integer(newCount), WebRequest.SCOPE_REQUEST);
		}
		else {
			logger.debug("Opening JPA EntityManager in OpenEntityManagerInViewInterceptor");
			try {
				EntityManager em = createEntityManager();
				TransactionSynchronizationManager.bindResource(getEntityManagerFactory(), new EntityManagerHolder(em));
			}
			catch (PersistenceException ex) {
				throw new DataAccessResourceFailureException("Could not create JPA EntityManager", ex);
			}
		}
	}

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

	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 EntityManager: just clear the marker.
			if (count.intValue() > 1) {
				request.setAttribute(participateAttributeName, new Integer(count.intValue() - 1), WebRequest.SCOPE_REQUEST);
			}
			else {
				request.removeAttribute(participateAttributeName, WebRequest.SCOPE_REQUEST);
			}
		}
		else {
			EntityManagerHolder emHolder = (EntityManagerHolder)
					TransactionSynchronizationManager.unbindResource(getEntityManagerFactory());
			logger.debug("Closing JPA EntityManager in OpenEntityManagerInViewInterceptor");
			EntityManagerFactoryUtils.closeEntityManager(emHolder.getEntityManager());
		}
	}

	/**
	 * Return the name of the request attribute that identifies that a request is
	 * already filtered. Default implementation takes the toString representation
	 * of the EntityManagerFactory instance and appends ".FILTERED".
	 * @see #PARTICIPATE_SUFFIX
	 */
	protected String getParticipateAttributeName() {
		return getEntityManagerFactory().toString() + PARTICIPATE_SUFFIX;
	}

}