001/* 002 * Copyright 2002-2018 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 022import org.springframework.lang.Nullable; 023 024/** 025 * MVC framework SPI, allowing parameterization of the core MVC workflow. 026 * 027 * <p>Interface that must be implemented for each handler type to handle a request. 028 * This interface is used to allow the {@link DispatcherServlet} to be indefinitely 029 * extensible. The {@code DispatcherServlet} accesses all installed handlers through 030 * this interface, meaning that it does not contain code specific to any handler type. 031 * 032 * <p>Note that a handler can be of type {@code Object}. This is to enable 033 * handlers from other frameworks to be integrated with this framework without 034 * custom coding, as well as to allow for annotation-driven handler objects that 035 * do not obey any specific Java interface. 036 * 037 * <p>This interface is not intended for application developers. It is available 038 * to handlers who want to develop their own web workflow. 039 * 040 * <p>Note: {@code HandlerAdapter} implementors may implement the {@link 041 * org.springframework.core.Ordered} interface to be able to specify a sorting 042 * order (and thus a priority) for getting applied by the {@code DispatcherServlet}. 043 * Non-Ordered instances get treated as lowest priority. 044 * 045 * @author Rod Johnson 046 * @author Juergen Hoeller 047 * @see org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter 048 * @see org.springframework.web.servlet.handler.SimpleServletHandlerAdapter 049 */ 050public interface HandlerAdapter { 051 052 /** 053 * Given a handler instance, return whether or not this {@code HandlerAdapter} 054 * can support it. Typical HandlerAdapters will base the decision on the handler 055 * type. HandlerAdapters will usually only support one handler type each. 056 * <p>A typical implementation: 057 * <p>{@code 058 * return (handler instanceof MyHandler); 059 * } 060 * @param handler the handler object to check 061 * @return whether or not this object can use the given handler 062 */ 063 boolean supports(Object handler); 064 065 /** 066 * Use the given handler to handle this request. 067 * The workflow that is required may vary widely. 068 * @param request current HTTP request 069 * @param response current HTTP response 070 * @param handler the handler to use. This object must have previously been passed 071 * to the {@code supports} method of this interface, which must have 072 * returned {@code true}. 073 * @throws Exception in case of errors 074 * @return a ModelAndView object with the name of the view and the required 075 * model data, or {@code null} if the request has been handled directly 076 */ 077 @Nullable 078 ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception; 079 080 /** 081 * Same contract as for HttpServlet's {@code getLastModified} method. 082 * Can simply return -1 if there's no support in the handler class. 083 * @param request current HTTP request 084 * @param handler the handler to use 085 * @return the lastModified value for the given handler 086 * @see javax.servlet.http.HttpServlet#getLastModified 087 * @see org.springframework.web.servlet.mvc.LastModified#getLastModified 088 */ 089 long getLastModified(HttpServletRequest request, Object handler); 090 091}