01: /*
02: * This file is part of the Echo Web Application Framework (hereinafter "Echo").
03: * Copyright (C) 2002-2005 NextApp, Inc.
04: *
05: * Version: MPL 1.1/GPL 2.0/LGPL 2.1
06: *
07: * The contents of this file are subject to the Mozilla Public License Version
08: * 1.1 (the "License"); you may not use this file except in compliance with
09: * the License. You may obtain a copy of the License at
10: * http://www.mozilla.org/MPL/
11: *
12: * Software distributed under the License is distributed on an "AS IS" basis,
13: * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
14: * for the specific language governing rights and limitations under the
15: * License.
16: *
17: * Alternatively, the contents of this file may be used under the terms of
18: * either the GNU General Public License Version 2 or later (the "GPL"), or
19: * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
20: * in which case the provisions of the GPL or the LGPL are applicable instead
21: * of those above. If you wish to allow use of your version of this file only
22: * under the terms of either the GPL or the LGPL, and not to allow others to
23: * use your version of this file under the terms of the MPL, indicate your
24: * decision by deleting the provisions above and replace them with the notice
25: * and other provisions required by the GPL or the LGPL. If you do not delete
26: * the provisions above, a recipient may use your version of this file under
27: * the terms of any one of the MPL, the GPL or the LGPL.
28: */
29:
30: package nextapp.echo2.webrender.service;
31:
32: import java.io.IOException;
33:
34: import nextapp.echo2.webrender.Connection;
35: import nextapp.echo2.webrender.ContentType;
36: import nextapp.echo2.webrender.Service;
37: import nextapp.echo2.webrender.UserInstance;
38:
39: /**
40: * Abstract base service for handling server poll requests to determine if any
41: * asynchronous operations affecting a <code>UserInstance</code> have been
42: * performed since the last server interaction, such that the client might
43: * resynchronize with the server.
44: * <p>
45: * An instance of this service must be registered with the
46: * <code>ServiceRegistry</code> if asynchronous polling is required.
47: */
48: public abstract class AsyncMonitorService implements Service {
49:
50: /**
51: * Asynchronous monitoring service identifier.
52: */
53: public static final String SERVICE_ID = "Echo.AsyncMonitor";
54:
55: /**
56: * @see nextapp.echo2.webrender.Service#getId()
57: */
58: public String getId() {
59: return SERVICE_ID;
60: }
61:
62: /**
63: * @see nextapp.echo2.webrender.Service#getVersion()
64: */
65: public int getVersion() {
66: return DO_NOT_CACHE;
67: }
68:
69: /**
70: * Determines if the specified <code>UserInstance</code> requires
71: * immediate synchronization.
72: *
73: * @param userInstance the <code>UserInstance</code>
74: * @return true if the <code>UserInstance</code> requires immediate
75: * client-server synchronization
76: */
77: protected abstract boolean isSynchronizationRequired(
78: UserInstance userInstance);
79:
80: /**
81: * @see nextapp.echo2.webrender.Service#service(nextapp.echo2.webrender.Connection)
82: */
83: public void service(Connection conn) throws IOException {
84: conn.setContentType(ContentType.TEXT_XML);
85: if (isSynchronizationRequired(conn.getUserInstance())) {
86: conn.getWriter().write(
87: "<async-monitor request-sync=\"true\"/>");
88: } else {
89: conn.getWriter().write(
90: "<async-monitor request-sync=\"false\"/>");
91: }
92: }
93: }
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