/*
 * Copyright 2002-2015 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.springframework.context.i18n.LocaleContextHolder;

Servlet listener that exposes the request to the current thread, through both LocaleContextHolder and RequestContextHolder. To be registered as listener in web.xml. 
Alternatively, Spring's RequestContextFilter and Spring's DispatcherServlet also expose the same request context to the current thread. In contrast to this listener, advanced options are available there (e.g. "threadContextInheritable"). 
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
See Also:
ServletRequestListener
LocaleContextHolder
RequestContextHolder
RequestContextFilter
DispatcherServlet
Since:
2.0/**
 * Servlet 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}.
 *
 * <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 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";


	@Override
	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);
	}

	@Override
	public void requestDestroyed(ServletRequestEvent requestEvent) {
		ServletRequestAttributes attributes = null;
		Object reqAttr = requestEvent.getServletRequest().getAttribute(REQUEST_ATTRIBUTES_ATTRIBUTE);
		if (reqAttr instanceof ServletRequestAttributes) {
			attributes = (ServletRequestAttributes) reqAttr;
		}
		RequestAttributes threadAttributes = RequestContextHolder.getRequestAttributes();
		if (threadAttributes != null) {
			// We're assumably within the original request thread...
			LocaleContextHolder.resetLocaleContext();
			RequestContextHolder.resetRequestAttributes();
			if (attributes == null && threadAttributes instanceof ServletRequestAttributes) {
				attributes = (ServletRequestAttributes) threadAttributes;
			}
		}
		if (attributes != null) {
			attributes.requestCompleted();
		}
	}

}