org.springframework.web.servlet.HandlerAdapter Maven / Gradle / Ivy
/*
* 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.
*
* 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.
*
*
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.
*
*
This interface is not intended for application developers. It is available
* to handlers who want to develop their own web workflow.
*
*
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.
*
A typical implementation:
*
{@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);
}