org.springframework.web.servlet.HandlerMapping Maven / Gradle / Ivy
/*
* Copyright 2002-2004 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.
*/
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 BeanNameUrlHandlerMapping and 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 HandlerExecutionChain
* instance, optionally accompanied by some 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 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 {
/**
* 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;
}