/*
* Copyright 2002-2008 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;
import javax.servlet.http.HttpServletResponse;
/**
* MVC framework SPI interface, allowing parameterization of core MVC workflow.
*
* <p>Interface that must be implemented for each handler type to handle a request.
* This interface is used to allow the {@link DispatcherServlet} to be indefinitely
* extensible. The DispatcherServlet accesses all installed handlers through this
* interface, meaning that it does not contain code specific to any handler type.
*
* <p>Note that a handler can be of type <code>Object</code>. This is to enable
* handlers from other frameworks to be integrated with this framework without
* custom coding, as well as to allow for annotation handler objects that do
* not obey any specific Java interface.
*
* <p>This interface is not intended for application developers. It is available
* to handlers who want to develop their own web workflow.
*
* <p>Note: HandlerAdaptger implementators may 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.web.servlet.mvc.SimpleControllerHandlerAdapter
* @see org.springframework.web.servlet.handler.SimpleServletHandlerAdapter
*/
public interface HandlerAdapter {
/**
* Given a handler instance, return whether or not this HandlerAdapter can
* support it. Typical HandlerAdapters will base the decision on the handler
* type. HandlerAdapters will usually only support one handler type each.
* <p>A typical implementation:
* <p><code>
* return (handler instanceof MyHandler);
* </code>
* @param handler handler object to check
* @return whether or not this object can use the given handler
*/
boolean supports(Object handler);
/**
* Use the given handler to handle this request.
* The workflow that is required may vary widely.
* @param request current HTTP request
* @param response current HTTP response
* @param handler handler to use. This object must have previously been passed
* to the <code>supports</code> method of this interface, which must have
* returned <code>true</code>.
* @throws Exception in case of errors
* @return ModelAndView object with the name of the view and the required
* model data, or <code>null</code> if the request has been handled directly
*/
ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception;
/**
* Same contract as for HttpServlet's <code>getLastModified</code> method.
* Can simply return -1 if there's no support in the handler class.
* @param request current HTTP request
* @param handler handler to use
* @return the lastModified value for the given handler
* @see javax.servlet.http.HttpServlet#getLastModified
* @see org.springframework.web.servlet.mvc.LastModified#getLastModified
*/
long getLastModified(HttpServletRequest request, Object handler);
}
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