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


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 com.caucho.loader.EnvironmentClassLoader;
32
33 import javax.el.ELContext;
34 import javax.el.ELResolver;
35
36 /**
37  * Creates a variable resolver based on the classloader.
38  */
39 public class EnvironmentResolver extends AbstractVariableResolver {
40   private ClassLoader JavaDoc _loader;
41   
42   /**
43    * Creates the resolver
44    */
45   public EnvironmentResolver(ClassLoader JavaDoc loader, ELResolver parent)
46   {
47     super(parent);
48     
49     _loader = loader;
50   }
51   
52   /**
53    * Returns the named variable value.
54    */
55   public Object JavaDoc getValue(ELContext context,
56              Object JavaDoc base,
57              Object JavaDoc property)
58   {
59     String JavaDoc var = (String JavaDoc) base;
60     
61     for (ClassLoader JavaDoc loader = _loader;
62      loader != null;
63      loader = loader.getParent()) {
64       if (loader instanceof EnvironmentClassLoader) {
65     Object JavaDoc value = EL.getLevelVar(var, loader);
66
67     if (value == EL.NULL)
68       return null;
69     else if (value != null)
70       return value;
71       }
72     }
73
74     Object JavaDoc value = EL.getLevelVar(var, null);
75     
76     if (value == EL.NULL)
77       return null;
78     else if (value != null)
79       return value;
80     else
81       return super.getValue(context, var, property);
82   }
83 }
84
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