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1 /**
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.geronimo.system.configuration.condition;
18
19 import java.util.HashMap;
20 import java.util.Map;
21 import java.util.Properties;
22
23 import org.apache.commons.jexl.Expression;
24 import org.apache.commons.jexl.ExpressionFactory;
25 import org.apache.commons.jexl.JexlContext;
26 import org.apache.commons.jexl.JexlHelper;
27 import org.apache.commons.jexl.context.HashMapContext;
28 import org.slf4j.Logger;
29 import org.slf4j.LoggerFactory;
30
31 /**
32 * Provides a simple facility to evaluate condition expressions using the
33 * <a href="http://jakarta.apache.org/commons/jexl">Jexl</a> language.
34 *
35 * <p>
36 * This class is thread-safe.
37 * </p>
38 *
39 * @version $Rev: 653740 $ $Date: 2008-05-06 03:44:18 -0700 (Tue, 06 May 2008) $
40 */
41 public class JexlConditionParser
42 implements ConditionParser
43 {
44 private static final Logger log = LoggerFactory.getLogger(JexlConditionParser.class);
45
46 private final Map<String, Object> vars;
47
48 public JexlConditionParser(final Map vars) {
49 if (vars == null) {
50 throw new IllegalArgumentException("vars");
51 }
52 this.vars = vars;
53 }
54
55 public JexlConditionParser() {
56 // Setup the default vars
57 vars = new HashMap<String, Object>();
58 ParserUtils.addDefaultVariables(vars);
59 }
60
61 /**
62 * Evaluate a condition expression.
63 *
64 * @param expression The condition expression to evaluate; must not be null
65 * @return True if the condition is satisfied
66 *
67 * @throws org.apache.geronimo.system.configuration.condition.ConditionParserException Failed to evaluate condition expression
68 */
69 public boolean evaluate(final String expression) throws ConditionParserException {
70 if (expression == null) {
71 throw new IllegalArgumentException("Expression must not be null");
72 }
73
74 // Empty expressions are true
75 if (expression.trim().length() == 0) {
76 log.debug("Expression is empty; skipping evaluation");
77
78 return true;
79 }
80
81 Object result;
82 try {
83 result = doEvaluate(expression);
84 }
85 catch (Exception e) {
86 throw new ConditionParserException("Failed to evaluate expression: " + expression, e);
87 }
88
89 if (result instanceof Boolean) {
90 return (Boolean) result;
91 }
92 else {
93 throw new ConditionParserException("Expression '" + expression + "' did not evaluate to a boolean value; found: " + result);
94 }
95 }
96
97 private Object doEvaluate(final String expression) throws Exception {
98 assert expression != null;
99
100 log.debug("Evaluating expression: {}", expression);
101
102 Expression expr = ExpressionFactory.createExpression(expression);
103
104 JexlContext ctx = JexlHelper.createContext();
105 ctx.setVars(vars);
106
107 Object result = expr.evaluate(ctx);
108 log.debug("Result: {}", result);
109
110 return result;
111 }
112 }