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 java.util.Map; 020import javax.servlet.http.HttpServletRequest; 021import javax.servlet.http.HttpServletResponse; 022 023/** 024 * MVC View for a web interaction. Implementations are responsible for rendering 025 * content, and exposing the model. A single view exposes multiple model attributes. 026 * 027 * <p>This class and the MVC approach associated with it is discussed in Chapter 12 of 028 * <a href="https://www.amazon.com/exec/obidos/tg/detail/-/0764543857/">Expert One-On-One J2EE Design and Development</a> 029 * by Rod Johnson (Wrox, 2002). 030 * 031 * <p>View implementations may differ widely. An obvious implementation would be 032 * JSP-based. Other implementations might be XSLT-based, or use an HTML generation library. 033 * This interface is designed to avoid restricting the range of possible implementations. 034 * 035 * <p>Views should be beans. They are likely to be instantiated as beans by a ViewResolver. 036 * As this interface is stateless, view implementations should be thread-safe. 037 * 038 * @author Rod Johnson 039 * @author Arjen Poutsma 040 * @author Rossen Stoyanchev 041 * @see org.springframework.web.servlet.view.AbstractView 042 * @see org.springframework.web.servlet.view.InternalResourceView 043 */ 044public interface View { 045 046 /** 047 * Name of the {@link HttpServletRequest} attribute that contains the response status code. 048 * <p>Note: This attribute is not required to be supported by all View implementations. 049 * @since 3.0 050 */ 051 String RESPONSE_STATUS_ATTRIBUTE = View.class.getName() + ".responseStatus"; 052 053 /** 054 * Name of the {@link HttpServletRequest} attribute that contains a Map with path variables. 055 * The map consists of String-based URI template variable names as keys and their corresponding 056 * Object-based values -- extracted from segments of the URL and type converted. 057 * <p>Note: This attribute is not required to be supported by all View implementations. 058 * @since 3.1 059 */ 060 String PATH_VARIABLES = View.class.getName() + ".pathVariables"; 061 062 /** 063 * The {@link org.springframework.http.MediaType} selected during content negotiation, 064 * which may be more specific than the one the View is configured with. For example: 065 * "application/vnd.example-v1+xml" vs "application/*+xml". 066 * @since 3.2 067 */ 068 String SELECTED_CONTENT_TYPE = View.class.getName() + ".selectedContentType"; 069 070 071 /** 072 * Return the content type of the view, if predetermined. 073 * <p>Can be used to check the view's content type upfront, 074 * i.e. before an actual rendering attempt. 075 * @return the content type String (optionally including a character set), 076 * or {@code null} if not predetermined 077 */ 078 String getContentType(); 079 080 /** 081 * Render the view given the specified model. 082 * <p>The first step will be preparing the request: In the JSP case, this would mean 083 * setting model objects as request attributes. The second step will be the actual 084 * rendering of the view, for example including the JSP via a RequestDispatcher. 085 * @param model Map with name Strings as keys and corresponding model 086 * objects as values (Map can also be {@code null} in case of empty model) 087 * @param request current HTTP request 088 * @param response HTTP response we are building 089 * @throws Exception if rendering failed 090 */ 091 void render(Map<String, ?> model, HttpServletRequest request, HttpServletResponse response) throws Exception; 092 093}