HandlerAdapter


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.servlet;
18  
19  import javax.servlet.http.HttpServletRequest  ;
20  import javax.servlet.http.HttpServletResponse  ;
21  
22  /**
23   * MVC framework SPI interface, allowing parameterization of core MVC workflow.
24   *
25   * <p>Interface that must be implemented for each handler type to handle a request.
26   * This interface is used to allow the DispatcherServlet to be indefinitely
27   * extensible. The DispatcherServlet accesses all installed handlers through this
28   * interface, meaning that it does not contain code specific to any handler type.
29   *
30   * <p>Note that a handler can be of type Object. This is to enable handlers from
31   * other frameworks to be integrated with this framework without custom coding.
32   *
33   * <p>This interface is not intended for application developers. It is available
34   * to handlers who want to develop their own web workflow.
35   *
36   * <p>Note: Implementations can implement the Ordered interface to be able to
37   * specify a sorting order and thus a priority for getting applied by
38   * DispatcherServlet. Non-Ordered instances get treated as lowest priority.
39   *
40   * @author Rod Johnson
41   * @author Juergen Hoeller
42   * @see org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter
43   * @see org.springframework.web.servlet.mvc.throwaway.ThrowawayControllerHandlerAdapter
44   * @see org.springframework.web.servlet.handler.SimpleServletHandlerAdapter
45   */
46  public interface HandlerAdapter {
47      
48      /**
49       * Given a handler instance, return whether or not this HandlerAdapter can
50       * support it. Typical HandlerAdapters will base the decision on the handler
51       * type. HandlerAdapters will usually only support one handler type each.
52       * <p>A typical implementation:
53       * <p><code>
54       * return (handler instanceof MyHandler);
55       * </code>
56       * @param handler handler object to check
57       * @return whether or not this object can use the given handler
58       */
59      boolean supports(Object   handler); 
60      
61      /**
62       * Use the given handler to handle this request.
63       * The workflow that is required may vary widely.
64       * @param request current HTTP request
65       * @param response current HTTP response
66       * @param handler handler to use. This object must have previously been passed
67       * to the <code>supports</code> method of this interface, which must have
68       * returned <code>true</code>.
69       * @throws Exception in case of errors
70       * @return ModelAndView object with the name of the view and the required
71       * model data, or <code>null</code> if the request has been handled directly
72       */
73      ModelAndView handle(HttpServletRequest   request, HttpServletResponse   response, Object   handler) throws Exception  ;
74  
75      /**
76       * Same contract as for HttpServlet's <code>getLastModified</code> method.
77       * Can simply return -1 if there's no support in the handler class.
78       * @param request current HTTP request
79       * @param handler handler to use
80       * @return the lastModified value for the given handler
81       * @see javax.servlet.http.HttpServlet#getLastModified
82       * @see org.springframework.web.servlet.mvc.LastModified#getLastModified
83       */
84      long getLastModified(HttpServletRequest   request, Object   handler);
85  
86  }
87
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