001/*
002 * Copyright 2002-2014 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.web;
018
019import java.io.IOException;
020import javax.servlet.ServletException;
021import javax.servlet.http.HttpServletRequest;
022import javax.servlet.http.HttpServletResponse;
023
024/**
025 * Plain handler interface for components that process HTTP requests,
026 * analogous to a Servlet. Only declares {@link javax.servlet.ServletException}
027 * and {@link java.io.IOException}, to allow for usage within any
028 * {@link javax.servlet.http.HttpServlet}. This interface is essentially the
029 * direct equivalent of an HttpServlet, reduced to a central handle method.
030 *
031 * <p>The easiest way to expose an HttpRequestHandler bean in Spring style
032 * is to define it in Spring's root web application context and define
033 * an {@link org.springframework.web.context.support.HttpRequestHandlerServlet}
034 * in {@code web.xml}, pointing to the target HttpRequestHandler bean
035 * through its {@code servlet-name} which needs to match the target bean name.
036 *
037 * <p>Supported as a handler type within Spring's
038 * {@link org.springframework.web.servlet.DispatcherServlet}, being able
039 * to interact with the dispatcher's advanced mapping and interception
040 * facilities. This is the recommended way of exposing an HttpRequestHandler,
041 * while keeping the handler implementations free of direct dependencies
042 * on a DispatcherServlet environment.
043 *
044 * <p>Typically implemented to generate binary responses directly,
045 * with no separate view resource involved. This differentiates it from a
046 * {@link org.springframework.web.servlet.mvc.Controller} within Spring's Web MVC
047 * framework. The lack of a {@link org.springframework.web.servlet.ModelAndView}
048 * return value gives a clearer signature to callers other than the
049 * DispatcherServlet, indicating that there will never be a view to render.
050 *
051 * <p>As of Spring 2.0, Spring's HTTP-based remote exporters, such as
052 * {@link org.springframework.remoting.httpinvoker.HttpInvokerServiceExporter}
053 * and {@link org.springframework.remoting.caucho.HessianServiceExporter},
054 * implement this interface rather than the more extensive Controller interface,
055 * for minimal dependencies on Spring-specific web infrastructure.
056 *
057 * <p>Note that HttpRequestHandlers may optionally implement the
058 * {@link org.springframework.web.servlet.mvc.LastModified} interface,
059 * just like Controllers can, <i>provided that they run within Spring's
060 * DispatcherServlet</i>. However, this is usually not necessary, since
061 * HttpRequestHandlers typically only support POST requests to begin with.
062 * Alternatively, a handler may implement the "If-Modified-Since" HTTP
063 * header processing manually within its {@code handle} method.
064 *
065 * @author Juergen Hoeller
066 * @since 2.0
067 * @see org.springframework.web.context.support.HttpRequestHandlerServlet
068 * @see org.springframework.web.servlet.DispatcherServlet
069 * @see org.springframework.web.servlet.ModelAndView
070 * @see org.springframework.web.servlet.mvc.Controller
071 * @see org.springframework.web.servlet.mvc.LastModified
072 * @see org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter
073 * @see org.springframework.remoting.httpinvoker.HttpInvokerServiceExporter
074 * @see org.springframework.remoting.caucho.HessianServiceExporter
075 * @see org.springframework.remoting.caucho.BurlapServiceExporter
076 */
077public interface HttpRequestHandler {
078
079        /**
080         * Process the given request, generating a response.
081         * @param request current HTTP request
082         * @param response current HTTP response
083         * @throws ServletException in case of general errors
084         * @throws IOException in case of I/O errors
085         */
086        void handleRequest(HttpServletRequest request, HttpServletResponse response)
087                        throws ServletException, IOException;
088
089}