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Java > Open Source Codes > org > apache > commons > jexl > resolver > FlatResolver


1 /*
2  * Copyright 2002-2006 The Apache Software Foundation.
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 package org.apache.commons.jexl.resolver;
17
18 import org.apache.commons.jexl.JexlExprResolver;
19 import org.apache.commons.jexl.JexlContext;
20
21 /**
22  * Simple resolver to try the expression as-is from the context.
23  *
24  * For example, you could resolve ant-ish properties (foo.bar.woogie)
25  * using this...
26  *
27  * hint, hint...
28  *
29  * @since 1.0
30  * @author <a HREF="mailto:geirm@adeptra.com">Geir Magnusson Jr.</a>
31  * @version $Id: FlatResolver.java 397542 2006-04-27 13:43:47Z dion $
32  */
33 public class FlatResolver implements JexlExprResolver {
34     /**
35      * Flag to return NO_VALUE on null from context.
36      * this allows jexl to try to evaluate
37      */
38     protected boolean noValOnNull = true;
39
40     /**
41      * Default CTOR.
42      */
43     public FlatResolver() {
44     }
45
46     /**
47      * CTOR that lets you override the default behavior of
48      * noValOnNull, which is true. (jexl gets a shot after if null)
49      *
50      * @param valOnNull Whether NO_VALUE will be returned instead of null.
51      */
52     public FlatResolver(boolean valOnNull) {
53         noValOnNull = valOnNull;
54     }
55
56     /**
57      * Try to resolve expression as-is.
58      *
59      * @param context The context for resolution.
60      * @param expression The flat expression.
61      * @return The resolved value.
62      */
63     public Object JavaDoc evaluate(JexlContext context, String JavaDoc expression) {
64         Object JavaDoc val = context.getVars().get(expression);
65
66         if (val == null && noValOnNull) {
67             return JexlExprResolver.NO_VALUE;
68         }
69
70         return val;
71     }
72 }
73
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