HttpRequestHandler


1   /*
2    * Copyright 2002-2006 the original author or authors.
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package org.springframework.web;
18  
19  import java.io.IOException  ;
20  
21  import javax.servlet.ServletException  ;
22  import javax.servlet.http.HttpServletRequest  ;
23  import javax.servlet.http.HttpServletResponse  ;
24  
25  /**
26   * Plain handler interface for components that process HTTP requests,
27   * analogous to a Servlet. Only throws ServletException and IOException,
28   * to allow for usage within any HttpServlet. Essentially the direct
29   * equivalent of an HttpServlet, reduced to a handle method.
30   *
31   * <p>The easiest way to expose an HttpRequestHandler bean in Spring style
32   * is to define it in Spring's root web application context and define
33   * an HttpRequestHandlerServlet in <code>web.xml</code>, pointing at the
34   * target HttpRequestHandler bean through its servlet-name which needs
35   * to match the target bean name.
36   *
37   * <p>Supported as a handler type within Spring's DispatcherServlet,
38   * being able to leverage the dispatcher's advanced mapping and interception
39   * facilities. This is the recommended way of exposing an HttpRequestHandler,
40   * while keeping the handler implementations free of direct dependencies
41   * on a DispatcherServlet environment.
42   *
43   * <p>Typically implemented to generate binary responses directly,
44   * with no separate view resource involved. This differentiates it from
45   * a Controller within Spring's Web MVC framework. The lack of a ModelAndView
46   * return value gives a clearer signature to callers other than the
47   * DispatcherServlet, indicating there will never be a view to render.
48   *
49   * <p>As of Spring 2.0, Spring's HTTP-based remote exporters, such as
50   * HttpInvokerServiceExporter and HessianServiceExporter, implement this
51   * interface rather than the more extensive Controller interface,
52   * for minimal dependencies on Spring-specific web infrastructure.
53   *
54   * <p>Note that RequestHandlers can optionally implement the LastModified
55   * interface, just like Controllers can, provided that they run within
56   * Spring's DispatcherServlet.
57   *
58   * @author Juergen Hoeller
59   * @since 2.0
60   * @see org.springframework.web.context.support.HttpRequestHandlerServlet
61   * @see org.springframework.web.servlet.DispatcherServlet
62   * @see org.springframework.web.servlet.ModelAndView
63   * @see org.springframework.web.servlet.mvc.Controller
64   * @see org.springframework.web.servlet.mvc.LastModified
65   * @see org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter
66   * @see org.springframework.remoting.httpinvoker.HttpInvokerServiceExporter
67   * @see org.springframework.remoting.caucho.HessianServiceExporter
68   * @see org.springframework.remoting.caucho.BurlapServiceExporter
69   */
70  public interface HttpRequestHandler {
71  
72      /**
73       * Process the given request, generating a response.
74       * @param request current HTTP request
75       * @param response current HTTP response
76       * @throws ServletException in case of general errors
77       * @throws IOException in case of I/O errors
78       */
79      void handleRequest(HttpServletRequest   request, HttpServletResponse   response)
80              throws ServletException  , IOException  ;
81  
82  }
83
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