01: /*
02: * Copyright 2002-2007 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:
21: /**
22: * Interface to be implemented by objects that define a mapping between
23: * requests and handler objects.
24: *
25: * <p>This class can be implemented by application developers, although this is not
26: * necessary, as {@link org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping}
27: * and {@link org.springframework.web.servlet.handler.SimpleUrlHandlerMapping}
28: * are included in the framework. The former is the default if no
29: * HandlerMapping bean is registered in the application context.
30: *
31: * <p>HandlerMapping implementations can support mapped interceptors but do not
32: * have to. A handler will always be wrapped in a {@link HandlerExecutionChain}
33: * instance, optionally accompanied by some {@link HandlerInterceptor} instances.
34: * The DispatcherServlet will first call each HandlerInterceptor's
35: * <code>preHandle</code> method in the given order, finally invoking the handler
36: * itself if all <code>preHandle</code> methods have returned <code>true</code>.
37: *
38: * <p>The ability to parameterize this mapping is a powerful and unusual
39: * capability of this MVC framework. For example, it is possible to write
40: * a custom mapping based on session state, cookie state or many other
41: * variables. No other MVC framework seems to be equally flexible.
42: *
43: * <p>Note: Implementations can implement the {@link org.springframework.core.Ordered}
44: * interface to be able to specify a sorting order and thus a priority for getting
45: * applied by DispatcherServlet. Non-Ordered instances get treated as lowest priority.
46: *
47: * @author Rod Johnson
48: * @author Juergen Hoeller
49: * @see org.springframework.core.Ordered
50: * @see org.springframework.web.servlet.handler.AbstractHandlerMapping
51: * @see org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping
52: * @see org.springframework.web.servlet.handler.SimpleUrlHandlerMapping
53: */
54: public interface HandlerMapping {
55:
56: /**
57: * Name of the {@link HttpServletRequest} attribute that contains the path
58: * within the handler mapping, in case of a pattern match, or the full
59: * relevant URI (typically within the DispatcherServlet's mapping) else.
60: * <p>Note: This attribute is not required to be supported by all
61: * HandlerMapping implementations. URL-based HandlerMappings will
62: * typically support it, but handlers should not necessarily expect
63: * this request attribute to be present in all scenarios.
64: */
65: String PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE = HandlerMapping.class
66: .getName()
67: + ".pathWithinHandlerMapping";
68:
69: /**
70: * Return a handler and any interceptors for this request. The choice may be made
71: * on request URL, session state, or any factor the implementing class chooses.
72: * <p>The returned HandlerExecutionChain contains a handler Object, rather than
73: * even a tag interface, so that handlers are not constrained in any way.
74: * For example, a HandlerAdapter could be written to allow another framework's
75: * handler objects to be used.
76: * <p>Returns <code>null</code> if no match was found. This is not an error.
77: * The DispatcherServlet will query all registered HandlerMapping beans to find
78: * a match, and only decide there is an error if none can find a handler.
79: * @param request current HTTP request
80: * @return a HandlerExecutionChain instance containing handler object and
81: * any interceptors, or <code>null</code> if no mapping found
82: * @throws Exception if there is an internal error
83: */
84: HandlerExecutionChain getHandler(HttpServletRequest request)
85: throws Exception;
86:
87: }
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