001/* 002 * Copyright 2002-2013 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.web.servlet; 018 019import javax.servlet.http.HttpServletRequest; 020import javax.servlet.http.HttpServletResponse; 021 022/** 023 * MVC framework SPI, allowing parameterization of the core MVC workflow. 024 * 025 * <p>Interface that must be implemented for each handler type to handle a request. 026 * This interface is used to allow the {@link DispatcherServlet} to be indefinitely 027 * extensible. The {@code DispatcherServlet} accesses all installed handlers through 028 * this interface, meaning that it does not contain code specific to any handler type. 029 * 030 * <p>Note that a handler can be of type {@code Object}. This is to enable 031 * handlers from other frameworks to be integrated with this framework without 032 * custom coding, as well as to allow for annotation-driven handler objects that 033 * do not obey any specific Java interface. 034 * 035 * <p>This interface is not intended for application developers. It is available 036 * to handlers who want to develop their own web workflow. 037 * 038 * <p>Note: {@code HandlerAdapter} implementors may implement the {@link 039 * org.springframework.core.Ordered} interface to be able to specify a sorting 040 * order (and thus a priority) for getting applied by the {@code DispatcherServlet}. 041 * Non-Ordered instances get treated as lowest priority. 042 * 043 * @author Rod Johnson 044 * @author Juergen Hoeller 045 * @see org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter 046 * @see org.springframework.web.servlet.handler.SimpleServletHandlerAdapter 047 */ 048public interface HandlerAdapter { 049 050 /** 051 * Given a handler instance, return whether or not this {@code HandlerAdapter} 052 * can support it. Typical HandlerAdapters will base the decision on the handler 053 * type. HandlerAdapters will usually only support one handler type each. 054 * <p>A typical implementation: 055 * <p>{@code 056 * return (handler instanceof MyHandler); 057 * } 058 * @param handler handler object to check 059 * @return whether or not this object can use the given handler 060 */ 061 boolean supports(Object handler); 062 063 /** 064 * Use the given handler to handle this request. 065 * The workflow that is required may vary widely. 066 * @param request current HTTP request 067 * @param response current HTTP response 068 * @param handler handler to use. This object must have previously been passed 069 * to the {@code supports} method of this interface, which must have 070 * returned {@code true}. 071 * @throws Exception in case of errors 072 * @return ModelAndView object with the name of the view and the required 073 * model data, or {@code null} if the request has been handled directly 074 */ 075 ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception; 076 077 /** 078 * Same contract as for HttpServlet's {@code getLastModified} method. 079 * Can simply return -1 if there's no support in the handler class. 080 * @param request current HTTP request 081 * @param handler handler to use 082 * @return the lastModified value for the given handler 083 * @see javax.servlet.http.HttpServlet#getLastModified 084 * @see org.springframework.web.servlet.mvc.LastModified#getLastModified 085 */ 086 long getLastModified(HttpServletRequest request, Object handler); 087 088}