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/*
 * Copyright 2002-2007 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.
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package org.springframework.web.servlet;

import javax.servlet.http.HttpServletRequest;

/**
 * Interface to be implemented by objects that define a mapping between
 * requests and handler objects.
 *
 * 

This class can be implemented by application developers, although this is not * necessary, as {@link org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping} * and {@link org.springframework.web.servlet.handler.SimpleUrlHandlerMapping} * are included in the framework. The former is the default if no * HandlerMapping bean is registered in the application context. * *

HandlerMapping implementations can support mapped interceptors but do not * have to. A handler will always be wrapped in a {@link HandlerExecutionChain} * instance, optionally accompanied by some {@link HandlerInterceptor} instances. * The DispatcherServlet will first call each HandlerInterceptor's * preHandle method in the given order, finally invoking the handler * itself if all preHandle methods have returned true. * *

The ability to parameterize this mapping is a powerful and unusual * capability of this MVC framework. For example, it is possible to write * a custom mapping based on session state, cookie state or many other * variables. No other MVC framework seems to be equally flexible. * *

Note: Implementations can implement the {@link org.springframework.core.Ordered} * interface to be able to specify a sorting order and thus a priority for getting * applied by DispatcherServlet. Non-Ordered instances get treated as lowest priority. * * @author Rod Johnson * @author Juergen Hoeller * @see org.springframework.core.Ordered * @see org.springframework.web.servlet.handler.AbstractHandlerMapping * @see org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping * @see org.springframework.web.servlet.handler.SimpleUrlHandlerMapping */ public interface HandlerMapping { /** * Name of the {@link HttpServletRequest} attribute that contains the path * within the handler mapping, in case of a pattern match, or the full * relevant URI (typically within the DispatcherServlet's mapping) else. *

Note: This attribute is not required to be supported by all * HandlerMapping implementations. URL-based HandlerMappings will * typically support it, but handlers should not necessarily expect * this request attribute to be present in all scenarios. */ String PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE = HandlerMapping.class.getName() + ".pathWithinHandlerMapping"; /** * Return a handler and any interceptors for this request. The choice may be made * on request URL, session state, or any factor the implementing class chooses. *

The returned HandlerExecutionChain contains a handler Object, rather than * even a tag interface, so that handlers are not constrained in any way. * For example, a HandlerAdapter could be written to allow another framework's * handler objects to be used. *

Returns null if no match was found. This is not an error. * The DispatcherServlet will query all registered HandlerMapping beans to find * a match, and only decide there is an error if none can find a handler. * @param request current HTTP request * @return a HandlerExecutionChain instance containing handler object and * any interceptors, or null if no mapping found * @throws Exception if there is an internal error */ HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception; }





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