Externalizer


1   /*
2    * $Id: Externalizer.java,v 1.3 2004/12/01 07:54:08 hengels Exp $
3    * Copyright 2000,2005 wingS development team.
4    *
5    * This file is part of wingS (http://www.j-wings.org).
6    *
7    * wingS is free software; you can redistribute it and/or modify
8    * it under the terms of the GNU Lesser General Public License
9    * as published by the Free Software Foundation; either version 2.1
10   * of the License, or (at your option) any later version.
11   *
12   * Please see COPYING for the complete licence.
13   */
14  package org.wings.externalizer;
15  
16  import org.wings.io.Device;
17  
18  import java.io.IOException  ;
19  import java.util.Collection  ;
20  
21  /**
22   * Externalizer Interface
23   * <p/>
24   * The {@link ExternalizeManager} uses a Externalizer to deliver an
25   * external representation of a java object to the output device (usually
26   * an HTTP connection).
27   * A SFrame'es external representation would be HTML, an Images content the
28   * GIF-byte stream, for instance.
29   * <p/>
30   * <p>An Externalizer must be
31   * {@link ExternalizeManager#addExternalizer(Externalizer) registered} at the
32   * {@link ExternalizeManager} of the current
33   * {@link org.wings.session.Session Session} to work seamlessly.
34   * <p/>
35   * Each Externalizer supports one or more classes it is able to externalize.
36   *
37   * @author <a HREF="mailto:mreinsch@to.com">Michael Reinsch</a>
38   * @author <a HREF="mailto:haaf@mercatis.de">Armin Haaf</a>
39   * @version $Revision: 1.3 $
40   */
41  public interface Externalizer {
42      /**
43       * Returns the file extension of the given object. Some (old) browsers use
44       * this information instead of the mime type. This is especially necessary
45       * if delivering anything different than HTML.
46       */
47      String   getExtension(Object   obj);
48  
49      /**
50       * returns the mime type of the given object.
51       */
52      String   getMimeType(Object   obj);
53  
54      /**
55       * Returns the externalized length of this Object. This value is set as
56       * content length in the HttpServletResponse. If it return -1 no content
57       * length is set.
58       */
59      int getLength(Object   obj);
60  
61      /**
62       * Returns true if the object is final, false if transient. It is used to
63       * control the caching in the browser.
64       */
65      boolean isFinal(Object   obj);
66  
67      /**
68       * Writes the given object into the given Device.
69       */
70      void write(Object   obj, Device out)
71              throws IOException  ;
72  
73      /**
74       * Returns the supported classes. The {@link ExternalizeManager}
75       * chooses the Externalizer (if not specified as parameter) by objects
76       * class.
77       */
78      Class  [] getSupportedClasses();
79  
80      /**
81       * Returns the supported mime types. The {@link ExternalizeManager}
82       * chooses the Externalizer by mime type (if specified as parameter)
83       */
84      String  [] getSupportedMimeTypes();
85  
86      /**
87       * Get additional http-headers.
88       * Returns <tt>null</tt>, if there are no additional headers to be set.
89       *
90       * @param obj get headers for this object
91       * @return Set of {@link java.util.Map.Entry} (key-value pairs)
92       */
93      Collection   getHeaders(Object   obj);
94  }
95  
96  
97
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