001/*
002 * Copyright 2002-2016 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;
020
021import javax.servlet.ServletException;
022import javax.servlet.http.HttpServletRequest;
023import javax.servlet.http.HttpServletResponse;
024
025/**
026 * Plain handler interface for components that process HTTP requests,
027 * analogous to a Servlet. Only declares {@link javax.servlet.ServletException}
028 * and {@link java.io.IOException}, to allow for usage within any
029 * {@link javax.servlet.http.HttpServlet}. This interface is essentially the
030 * direct equivalent of an HttpServlet, reduced to a central handle method.
031 *
032 * <p>The easiest way to expose an HttpRequestHandler bean in Spring style
033 * is to define it in Spring's root web application context and define
034 * an {@link org.springframework.web.context.support.HttpRequestHandlerServlet}
035 * in {@code web.xml}, pointing to the target HttpRequestHandler bean
036 * through its {@code servlet-name} which needs to match the target bean name.
037 *
038 * <p>Supported as a handler type within Spring's
039 * {@link org.springframework.web.servlet.DispatcherServlet}, being able
040 * to interact with the dispatcher's advanced mapping and interception
041 * facilities. This is the recommended way of exposing an HttpRequestHandler,
042 * while keeping the handler implementations free of direct dependencies
043 * on a DispatcherServlet environment.
044 *
045 * <p>Typically implemented to generate binary responses directly,
046 * with no separate view resource involved. This differentiates it from a
047 * {@link org.springframework.web.servlet.mvc.Controller} within Spring's Web MVC
048 * framework. The lack of a {@link org.springframework.web.servlet.ModelAndView}
049 * return value gives a clearer signature to callers other than the
050 * DispatcherServlet, indicating that there will never be a view to render.
051 *
052 * <p>As of Spring 2.0, Spring's HTTP-based remote exporters, such as
053 * {@link org.springframework.remoting.httpinvoker.HttpInvokerServiceExporter}
054 * and {@link org.springframework.remoting.caucho.HessianServiceExporter},
055 * implement this interface rather than the more extensive Controller interface,
056 * for minimal dependencies on Spring-specific web infrastructure.
057 *
058 * <p>Note that HttpRequestHandlers may optionally implement the
059 * {@link org.springframework.web.servlet.mvc.LastModified} interface,
060 * just like Controllers can, <i>provided that they run within Spring's
061 * DispatcherServlet</i>. However, this is usually not necessary, since
062 * HttpRequestHandlers typically only support POST requests to begin with.
063 * Alternatively, a handler may implement the "If-Modified-Since" HTTP
064 * header processing manually within its {@code handle} method.
065 *
066 * @author Juergen Hoeller
067 * @since 2.0
068 * @see org.springframework.web.context.support.HttpRequestHandlerServlet
069 * @see org.springframework.web.servlet.DispatcherServlet
070 * @see org.springframework.web.servlet.ModelAndView
071 * @see org.springframework.web.servlet.mvc.Controller
072 * @see org.springframework.web.servlet.mvc.LastModified
073 * @see org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter
074 * @see org.springframework.remoting.httpinvoker.HttpInvokerServiceExporter
075 * @see org.springframework.remoting.caucho.HessianServiceExporter
076 */
077@FunctionalInterface
078public interface HttpRequestHandler {
079
080        /**
081         * Process the given request, generating a response.
082         * @param request current HTTP request
083         * @param response current HTTP response
084         * @throws ServletException in case of general errors
085         * @throws IOException in case of I/O errors
086         */
087        void handleRequest(HttpServletRequest request, HttpServletResponse response)
088                        throws ServletException, IOException;
089
090}