org.springframework.web.servlet.mvc.Controller Maven / Gradle / Ivy
/* * Copyright 2002-2006 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.mvc; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.springframework.web.servlet.ModelAndView; /** * Base Controller interface, representing a component that receives *
has received a request and has * done its work to resolve locales, themes and suchlike, it then tries * to resolve a Controller, using a * {@link org.springframework.web.servlet.HandlerMapping HandlerMapping}. * When a Controller has been found to handle the request, the * {@link #handleRequest(HttpServletRequest, HttpServletResponse) handleRequest} * method of the located Controller will be invoked; the located Controller * is then responsible for handling the actual request and - if applicable - * returning an appropriate * {@link org.springframework.web.servlet.ModelAndView ModelAndView}. * So actually, this method is the main entrypoint for the * {@link org.springframework.web.servlet.DispatcherServlet DispatcherServlet} * which delegates requests to controllers. This method - and also this interface - * should preferrably not be implemented by custom controllers directly, since * abstract controller also provided by this package already provide a lot of * functionality for typical use cases in web applications. A few examples of * those controllers: * {@link AbstractController AbstractController}, * {@link AbstractCommandController AbstractCommandController}, * {@link SimpleFormController SimpleFormController}. * *HttpServletRequest
andHttpServletResponse
* instances just like aHttpServlet
but is able to * participate in an MVC workflow. Controllers are comparable to the * notion of a StrutsAction
. * *Any implementation of the Controller interface should be a * reusable, thread-safe class, capable of handling multiple * HTTP requests throughout the lifecycle of an application. To be able to * configure a Controller easily, Controller implementations are encouraged * to be (and usually are) JavaBeans. *
* * * ** After a
DispatcherServlet So basically any direct implementation of the Controller interface * just handles HttpServletRequests and should return a ModelAndView, to be further * interpreted by the DispatcherServlet. Any additional functionality such as * optional validation, form handling, etc should be obtained through extending * one of the abstract controller classes mentioned above.
* *Notes on design and testing
* *The Controller interface is explicitly designed to operate on HttpServletRequest * and HttpServletResponse objects, just like an HttpServlet. It does not aim to * decouple itself from the Servlet API, in contrast to, for example, WebWork, JSF or Tapestry. * Instead, the full power of the Servlet API is available, allowing Controllers to be * general-purpose: a Controller is able to not only handle web user interface * requests but also to process remoting protocols or to generate reports on demand.
* *Controllers can easily be tested by passing in mock objects for the * HttpServletRequest and HttpServletResponse objects as parameters to the * {@link #handleRequest(HttpServletRequest, HttpServletResponse) handleRequest} * method. As a convenience, Spring ships with a set of Servlet API mocks * that are suitable for testing any kind of web components, but are particularly * suitable for testing Spring web controllers. In contrast to a Struts Action, * there is no need to mock the ActionServlet or any other infrastructure; * HttpServletRequest and HttpServletResponse are sufficient.
* *If Controllers need to be aware of specific environment references, they can * choose to implement specific awareness interfaces, just like any other bean in a * Spring (web) application context can do, for example:
*
-
*
org.springframework.context.ApplicationContextAware
* org.springframework.context.ResourceLoaderAware
* org.springframework.web.context.ServletContextAware
*
Such environment references can easily be passed in testing environments, * through the corresponding setters defined in the respective awareness interfaces. * In general, it is recommended to keep the dependencies as minimal as possible: * for example, if all you need is resource loading, implement ResourceLoaderAware only. * Alternatively, derive from the WebApplicationObjectSupport base class, which gives * you all those references through convenient accessors - but requires an * ApplicationContext reference on initialization. * *
Controllers can optionally implement the LastModified interface.
*
* @author Rod Johnson
* @author Juergen Hoeller
* @see LastModified
* @see SimpleControllerHandlerAdapter
* @see AbstractController
* @see AbstractCommandController
* @see SimpleFormController
* @see org.springframework.mock.web.MockHttpServletRequest
* @see org.springframework.mock.web.MockHttpServletResponse
* @see org.springframework.context.ApplicationContextAware
* @see org.springframework.context.ResourceLoaderAware
* @see org.springframework.web.context.ServletContextAware
* @see org.springframework.web.context.support.WebApplicationObjectSupport
*/
public interface Controller {
/**
* Process the request and return a ModelAndView object which the DispatcherServlet
* will render. A null
return value is not an error: It indicates that
* this object completed request processing itself, thus there is no ModelAndView
* to render.
* @param request current HTTP request
* @param response current HTTP response
* @return a ModelAndView to render, or null
if handled directly
* @throws Exception in case of errors
*/
ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception;
}