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;
17:
18: /**
19: * A Resolver allows custom resolution of the expression, and can be
20: * added in front of the jexl engine, or after in the evaluation.
21: *
22: * @todo This needs to be explained in detail. Why do this?
23: * @since 1.0
24: * @author <a href="mailto:geirm@adeptra.com">Geir Magnusson Jr.</a>
25: * @version $Id: JexlExprResolver.java 397092 2006-04-26 05:11:28Z dion $
26: */
27: public interface JexlExprResolver {
28: /** represents an expression result of no value. */
29: Object NO_VALUE = new Object();
30:
31: /**
32: * Evaluates an expression against the context.
33: *
34: * @todo Must detail the expectations and effects of this resolver.
35: * @param context current data context
36: * @param expression expression to evauluate
37: * @return value (may be null) or the NO_VALUE object to
38: * indicate no resolution.
39: */
40: Object evaluate(JexlContext context, String expression);
41: }
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