View


1   /*
2    * Copyright 2002-2005 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  
21  import javax.servlet.http.HttpServletRequest  ;
22  import javax.servlet.http.HttpServletResponse  ;
23  
24  /**
25   * MVC View for a web interaction. Implementations are responsible for rendering
26   * content, and exposing the model. A single view exposes multiple model attributes.
27   *
28   * <p>This class and the MVC approach associated with it is discussed in Chapter 12 of
29   * <a HREF="http://www.amazon.com/exec/obidos/tg/detail/-/0764543857/">Expert One-On-One J2EE Design and Development</a>
30   * by Rod Johnson (Wrox, 2002).
31   *
32   * <p>View implementations may differ widely. An obvious implementation would be
33   * JSP-based. Other implementations might be XSLT-based, or use an HTML generation library.
34   * This interface is designed to avoid restricting the range of possible implementations.
35   *
36   * <p>Views should be beans. They are likely to be instantiated as beans by a ViewResolver.
37   * As this interface is stateless, view implementations should be thread-safe.
38   *
39   * @author Rod Johnson
40   * @see org.springframework.web.servlet.view.AbstractView
41   * @see org.springframework.web.servlet.view.InternalResourceView
42   */
43  public interface View {
44  
45      /**
46       * Return the content type of the view, if predetermined.
47       * <p>Can be used to check the content type upfront,
48       * before the actual rendering process.
49       * @return the content type String (optionally including a character set),
50       * or <code>null</code> if not predetermined.
51       */
52      String   getContentType();
53  
54      /**
55       * Render the view given the specified model.
56       * <p>The first step will be preparing the request: In the JSP case,
57       * this would mean setting model objects as request attributes.
58       * The second step will be the actual rendering of the view,
59       * for example including the JSP via a RequestDispatcher.
60       * @param model Map with name Strings as keys and corresponding model
61       * objects as values (Map can also be <code>null</code> in case of empty model)
62       * @param request current HTTP request
63       * @param response HTTP response we are building
64       * @throws Exception if rendering failed
65       */
66      void render(Map   model, HttpServletRequest   request, HttpServletResponse   response) throws Exception  ;
67  
68  }
69
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