01: /*
02: * Copyright 2002-2006 The Apache Software Foundation.
03: *
04: * Licensed under the Apache License, Version 2.0 (the "License");
05: * you may not use this file except in compliance with the License.
06: * You may obtain a copy of the License at
07: *
08: * http://www.apache.org/licenses/LICENSE-2.0
09: *
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 evaluate(JexlContext context, String expression) {
64: Object val = context.getVars().get(expression);
65:
66: if (val == null && noValOnNull) {
67: return JexlExprResolver.NO_VALUE;
68: }
69:
70: return val;
71: }
72: }
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