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Java > Open Source Codes > com > caucho > el > SystemPropertiesResolver


1 /*
2  * Copyright (c) 1998-2006 Caucho Technology -- all rights reserved
3  *
4  * This file is part of Resin(R) Open Source
5  *
6  * Each copy or derived work must preserve the copyright notice and this
7  * notice unmodified.
8  *
9  * Resin Open Source is free software; you can redistribute it and/or modify
10  * it under the terms of the GNU General Public License as published by
11  * the Free Software Foundation; either version 2 of the License, or
12  * (at your option) any later version.
13  *
14  * Resin Open Source is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, or any warranty
17  * of NON-INFRINGEMENT. See the GNU General Public License for more
18  * details.
19  *
20  * You should have received a copy of the GNU General Public License
21  * along with Resin Open Source; if not, write to the
22  * Free SoftwareFoundation, Inc.
23  * 59 Temple Place, Suite 330
24  * Boston, MA 02111-1307 USA
25  *
26  * @author Scott Ferguson
27  */
28
29 package com.caucho.el;
30
31 import javax.el.ELContext;
32 import javax.el.ELResolver;
33
34 /**
35  * Variable resolver using the system properties (@link System#getProperty()}
36  * and the environment {@link System@getenv()}.
37  *
38  */
39 public class SystemPropertiesResolver extends AbstractVariableResolver {
40   /**
41    * Creates the resolver
42    */
43   public SystemPropertiesResolver()
44   {
45   }
46   
47   /**
48    * Creates the resolver
49    */
50   public SystemPropertiesResolver(ELResolver next)
51   {
52     super(next);
53   }
54   
55   /**
56    * Returns the named variable value.
57    */
58   @Override JavaDoc
59   public Object JavaDoc getValue(ELContext env,
60              Object JavaDoc base,
61              Object JavaDoc property)
62   {
63     String JavaDoc var;
64     
65     if (base == null && property instanceof String JavaDoc)
66       var = (String JavaDoc) property;
67     else if (base == this && property instanceof String JavaDoc)
68       var = (String JavaDoc) property;
69     else
70       return null;
71     
72     Object JavaDoc value = System.getProperty(var);
73
74     if (value != null) {
75       env.setPropertyResolved(true);
76       return value;
77     }
78
79     value = System.getenv(var);
80
81     if (value != null) {
82       env.setPropertyResolved(true);
83       return value;
84     }
85
86     if ("Var".equals(var)) {
87       env.setPropertyResolved(true);
88       return this;
89     }
90
91     return null;
92   }
93
94   /**
95    * Returns the system property resolver.
96    */
97   public String JavaDoc toString()
98   {
99     return "SystemPropertiesResolver[]";
100   }
101 }
102
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