/*
 * 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.web.context.request;

import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
import javax.servlet.http.HttpServletRequest;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.context.i18n.LocaleContextHolder;

/**
 * Servlet 2.4+ listener that exposes the request to the current thread,
 * through both {@link org.springframework.context.i18n.LocaleContextHolder} and
 * {@link RequestContextHolder}. To be registered as listener in <code>web.xml</code>.
 *
 * <p>Alternatively, Spring's {@link org.springframework.web.filter.RequestContextFilter}
 * and Spring's {@link org.springframework.web.servlet.DispatcherServlet} also expose
 * the same request context to the current thread. In contrast to this listener,
 * advanced options are available there (e.g. "threadContextInheritable").
 *
 * <p>This listener is mainly for use with third-party servlets, e.g. the JSF FacesServlet.
 * Within Spring's own web support, DispatcherServlet's processing is perfectly sufficient.
 *
 * @author Juergen Hoeller
 * @since 2.0
 * @see javax.servlet.ServletRequestListener
 * @see org.springframework.context.i18n.LocaleContextHolder
 * @see org.springframework.web.context.request.RequestContextHolder
 * @see org.springframework.web.filter.RequestContextFilter
 * @see org.springframework.web.servlet.DispatcherServlet
 */
public class RequestContextListener implements ServletRequestListener {

	private static final String REQUEST_ATTRIBUTES_ATTRIBUTE =
			RequestContextListener.class.getName() + ".REQUEST_ATTRIBUTES";

	/** Logger available to subclasses */
	protected final Log logger = LogFactory.getLog(getClass());


	public void requestInitialized(ServletRequestEvent requestEvent) {
		if (!(requestEvent.getServletRequest() instanceof HttpServletRequest)) {
			throw new IllegalArgumentException(
					"Request is not an HttpServletRequest: " + requestEvent.getServletRequest());
		}
		HttpServletRequest request = (HttpServletRequest) requestEvent.getServletRequest();
		ServletRequestAttributes attributes = new ServletRequestAttributes(request);
		request.setAttribute(REQUEST_ATTRIBUTES_ATTRIBUTE, attributes);
		LocaleContextHolder.setLocale(request.getLocale());
		RequestContextHolder.setRequestAttributes(attributes);
		if (logger.isDebugEnabled()) {
			logger.debug("Bound request context to thread: " + request);
		}
	}

	public void requestDestroyed(ServletRequestEvent requestEvent) {
		ServletRequestAttributes attributes =
				(ServletRequestAttributes) requestEvent.getServletRequest().getAttribute(REQUEST_ATTRIBUTES_ATTRIBUTE);
		ServletRequestAttributes threadAttributes =
				(ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
		if (threadAttributes != null) {
			// We're assumably within the original request thread...
			if (attributes == null) {
				attributes = threadAttributes;
			}
			RequestContextHolder.resetRequestAttributes();
			LocaleContextHolder.resetLocaleContext();
		}
		if (attributes != null) {
			attributes.requestCompleted();
			if (logger.isDebugEnabled()) {
				logger.debug("Cleared thread-bound request context: " + requestEvent.getServletRequest());
			}
		}
	}

}