https://github.com/spring-projects/spring-framework: Spring Web (Spring IO)
  • Juergen Hoeller 
/*
 * Copyright 2002-2016 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;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


Plain handler interface for components that process HTTP requests, analogous to a Servlet. Only declares ServletException and IOException, to allow for usage within any HttpServlet. This interface is essentially the direct equivalent of an HttpServlet, reduced to a central handle method. 
The easiest way to expose an HttpRequestHandler bean in Spring style is to define it in Spring's root web application context and define an HttpRequestHandlerServlet in web.xml, pointing to the target HttpRequestHandler bean through its servlet-name which needs to match the target bean name. 
Supported as a handler type within Spring's DispatcherServlet, being able to interact with the dispatcher's advanced mapping and interception facilities. This is the recommended way of exposing an HttpRequestHandler, while keeping the handler implementations free of direct dependencies on a DispatcherServlet environment. 
Typically implemented to generate binary responses directly, with no separate view resource involved. This differentiates it from a Controller within Spring's Web MVC framework. The lack of a ModelAndView return value gives a clearer signature to callers other than the DispatcherServlet, indicating that there will never be a view to render. 
As of Spring 2.0, Spring's HTTP-based remote exporters, such as HttpInvokerServiceExporter and HessianServiceExporter, implement this interface rather than the more extensive Controller interface, for minimal dependencies on Spring-specific web infrastructure. 
Note that HttpRequestHandlers may optionally implement the LastModified interface, just like Controllers can, provided that they run within Spring's
DispatcherServlet. However, this is usually not necessary, since HttpRequestHandlers typically only support POST requests to begin with. Alternatively, a handler may implement the "If-Modified-Since" HTTP header processing manually within its handle method. 
Author:Juergen Hoeller
See Also:
Since:2.0
/**
 * Plain handler interface for components that process HTTP requests,
 * analogous to a Servlet. Only declares {@link javax.servlet.ServletException}
 * and {@link java.io.IOException}, to allow for usage within any
 * {@link javax.servlet.http.HttpServlet}. This interface is essentially the
 * direct equivalent of an HttpServlet, reduced to a central handle method.
 *
 * <p>The easiest way to expose an HttpRequestHandler bean in Spring style
 * is to define it in Spring's root web application context and define
 * an {@link org.springframework.web.context.support.HttpRequestHandlerServlet}
 * in {@code web.xml}, pointing to the target HttpRequestHandler bean
 * through its {@code servlet-name} which needs to match the target bean name.
 *
 * <p>Supported as a handler type within Spring's
 * {@link org.springframework.web.servlet.DispatcherServlet}, being able
 * to interact with the dispatcher's advanced mapping and interception
 * facilities. This is the recommended way of exposing an HttpRequestHandler,
 * while keeping the handler implementations free of direct dependencies
 * on a DispatcherServlet environment.
 *
 * <p>Typically implemented to generate binary responses directly,
 * with no separate view resource involved. This differentiates it from a
 * {@link org.springframework.web.servlet.mvc.Controller} within Spring's Web MVC
 * framework. The lack of a {@link org.springframework.web.servlet.ModelAndView}
 * return value gives a clearer signature to callers other than the
 * DispatcherServlet, indicating that there will never be a view to render.
 *
 * <p>As of Spring 2.0, Spring's HTTP-based remote exporters, such as
 * {@link org.springframework.remoting.httpinvoker.HttpInvokerServiceExporter}
 * and {@link org.springframework.remoting.caucho.HessianServiceExporter},
 * implement this interface rather than the more extensive Controller interface,
 * for minimal dependencies on Spring-specific web infrastructure.
 *
 * <p>Note that HttpRequestHandlers may optionally implement the
 * {@link org.springframework.web.servlet.mvc.LastModified} interface,
 * just like Controllers can, <i>provided that they run within Spring's
 * DispatcherServlet</i>. However, this is usually not necessary, since
 * HttpRequestHandlers typically only support POST requests to begin with.
 * Alternatively, a handler may implement the "If-Modified-Since" HTTP
 * header processing manually within its {@code handle} method.
 *
 * @author Juergen Hoeller
 * @since 2.0
 * @see org.springframework.web.context.support.HttpRequestHandlerServlet
 * @see org.springframework.web.servlet.DispatcherServlet
 * @see org.springframework.web.servlet.ModelAndView
 * @see org.springframework.web.servlet.mvc.Controller
 * @see org.springframework.web.servlet.mvc.LastModified
 * @see org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter
 * @see org.springframework.remoting.httpinvoker.HttpInvokerServiceExporter
 * @see org.springframework.remoting.caucho.HessianServiceExporter
 */
@FunctionalInterface
public interface HttpRequestHandler {

	
Process the given request, generating a response.

Params:
  • request – current HTTP request
  • response – current HTTP response
Throws:
/**
	 * Process the given request, generating a response.
	 * @param request current HTTP request
	 * @param response current HTTP response
	 * @throws ServletException in case of general errors
	 * @throws IOException in case of I/O errors
	 */
	void handleRequest(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException;

}