1 /*
2 * Copyright 2002-2012 the original author or authors.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 package org.springframework.web.servlet;
18
19 import java.util.Map;
20 import javax.servlet.http.HttpServletRequest;
21 import javax.servlet.http.HttpServletResponse;
22
23 import org.springframework.http.MediaType;
24
25 /**
26 * MVC View for a web interaction. Implementations are responsible for rendering
27 * content, and exposing the model. A single view exposes multiple model attributes.
28 *
29 * <p>This class and the MVC approach associated with it is discussed in Chapter 12 of
30 * <a href="http://www.amazon.com/exec/obidos/tg/detail/-/0764543857/">Expert One-On-One J2EE Design and Development</a>
31 * by Rod Johnson (Wrox, 2002).
32 *
33 * <p>View implementations may differ widely. An obvious implementation would be
34 * JSP-based. Other implementations might be XSLT-based, or use an HTML generation library.
35 * This interface is designed to avoid restricting the range of possible implementations.
36 *
37 * <p>Views should be beans. They are likely to be instantiated as beans by a ViewResolver.
38 * As this interface is stateless, view implementations should be thread-safe.
39 *
40 * @author Rod Johnson
41 * @author Arjen Poutsma
42 * @see org.springframework.web.servlet.view.AbstractView
43 * @see org.springframework.web.servlet.view.InternalResourceView
44 */
45 public interface View {
46
47 /**
48 * Name of the {@link HttpServletRequest} attribute that contains the response status code.
49 * <p>Note: This attribute is not required to be supported by all View implementations.
50 */
51 String RESPONSE_STATUS_ATTRIBUTE = View.class.getName() + ".responseStatus";
52
53 /**
54 * Name of the {@link HttpServletRequest} attribute that contains a Map with path variables.
55 * The map consists of String-based URI template variable names as keys and their corresponding
56 * Object-based values -- extracted from segments of the URL and type converted.
57 *
58 * <p>Note: This attribute is not required to be supported by all View implementations.
59 */
60 String PATH_VARIABLES = View.class.getName() + ".pathVariables";
61
62 /**
63 * The {@link MediaType} selected during content negotiation, which may be
64 * more specific than the one the View is configured with. For example:
65 * "application/vnd.example-v1+xml" vs "application/*+xml".
66 */
67 String SELECTED_CONTENT_TYPE = View.class.getName() + ".selectedContentType";
68
69 /**
70 * Return the content type of the view, if predetermined.
71 * <p>Can be used to check the content type upfront,
72 * before the actual rendering process.
73 * @return the content type String (optionally including a character set),
74 * or {@code null} if not predetermined.
75 */
76 String getContentType();
77
78 /**
79 * Render the view given the specified model.
80 * <p>The first step will be preparing the request: In the JSP case,
81 * this would mean setting model objects as request attributes.
82 * The second step will be the actual rendering of the view,
83 * for example including the JSP via a RequestDispatcher.
84 * @param model Map with name Strings as keys and corresponding model
85 * objects as values (Map can also be {@code null} in case of empty model)
86 * @param request current HTTP request
87 * @param response HTTP response we are building
88 * @throws Exception if rendering failed
89 */
90 void render(Map<String, ?> model, HttpServletRequest request, HttpServletResponse response) throws Exception;
91
92 }