/*
* 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.servlet.mvc;
import javax.servlet.http.HttpServletRequest;
/**
* Supports last-modified HTTP requests to facilitate content caching.
* Same contract as for the Servlet API's <code>getLastModified</code> method.
*
* <p>Delegated to by a {@link org.springframework.web.servlet.HandlerAdapter#getLastModified}
* implementation. By default, any Controller or HttpRequestHandler within Spring's
* default framework can implement this interface to enable last-modified checking.
*
* <p><b>Note:</b> Alternative handler implementation approaches have different
* last-modified handling styles. For example, Spring 2.5's annotated controller
* approach (using <code>@RequestMapping</code>) provides last-modified support
* through the {@link org.springframework.web.context.request.WebRequest#checkNotModified}
* method, allowing for last-modified checking within the main handler method.
*
* @author Rod Johnson
* @author Juergen Hoeller
* @see javax.servlet.http.HttpServlet#getLastModified
* @see Controller
* @see SimpleControllerHandlerAdapter
* @see org.springframework.web.HttpRequestHandler
* @see HttpRequestHandlerAdapter
*/
public interface LastModified {
/**
* Same contract as for HttpServlet's <code>getLastModified</code> method.
* Invoked <b>before</b> request processing.
* <p>The return value will be sent to the HTTP client as Last-Modified header,
* and compared with If-Modified-Since headers that the client sends back.
* The content will only get regenerated if there has been a modification.
* @param request current HTTP request
* @return the time the underlying resource was last modified, or -1
* meaning that the content must always be regenerated
* @see org.springframework.web.servlet.HandlerAdapter#getLastModified
* @see javax.servlet.http.HttpServlet#getLastModified
*/
long getLastModified(HttpServletRequest request);
}
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