01: /*
02: * Copyright 2002-2006 the original author or authors.
03: *
04: * Licensed under the Apache License, Version 2.0 (the "License");
05: * you may not use this file except in compliance with the License.
06: * You may obtain a copy of the License at
07: *
08: * http://www.apache.org/licenses/LICENSE-2.0
09: *
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,
74: HttpServletResponse response, Object handler)
75: throws Exception;
76:
77: /**
78: * Same contract as for HttpServlet's <code>getLastModified</code> method.
79: * Can simply return -1 if there's no support in the handler class.
80: * @param request current HTTP request
81: * @param handler handler to use
82: * @return the lastModified value for the given handler
83: * @see javax.servlet.http.HttpServlet#getLastModified
84: * @see org.springframework.web.servlet.mvc.LastModified#getLastModified
85: */
86: long getLastModified(HttpServletRequest request, Object handler);
87:
88: }
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