Java tutorial
/* * Copyright 2002-2018 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 * * https://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; import org.springframework.lang.Nullable; /** * MVC framework SPI, allowing parameterization of the 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 {@code 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}. This is to enable * handlers from other frameworks to be integrated with this framework without * custom coding, as well as to allow for annotation-driven 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: {@code HandlerAdapter} implementors 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 the {@code 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 {@code 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); * } * @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} method of this interface, which must have * returned {@code true}. * @throws Exception in case of errors * @return a ModelAndView object with the name of the view and the required * model data, or {@code null} if the request has been handled directly */ @Nullable ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception; /** * Same contract as for HttpServlet's {@code getLastModified} 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); }