001 /** 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 package org.apache.geronimo.system.configuration.condition; 018 019 import java.util.HashMap; 020 import java.util.Map; 021 import java.util.Properties; 022 023 import org.apache.commons.jexl.Expression; 024 import org.apache.commons.jexl.ExpressionFactory; 025 import org.apache.commons.jexl.JexlContext; 026 import org.apache.commons.jexl.JexlHelper; 027 import org.apache.commons.jexl.context.HashMapContext; 028 import org.apache.commons.logging.Log; 029 import org.apache.commons.logging.LogFactory; 030 031 /** 032 * Provides a simple facility to evaluate condition expressions using the 033 * <a href="http://jakarta.apache.org/commons/jexl">Jexl</a> language. 034 * 035 * <p> 036 * This class is thread-safe. 037 * </p> 038 * 039 * @version $Rev: 706640 $ $Date: 2008-10-21 14:44:05 +0000 (Tue, 21 Oct 2008) $ 040 */ 041 public class JexlConditionParser 042 implements ConditionParser 043 { 044 private static final Log log = LogFactory.getLog(JexlConditionParser.class); 045 046 private final Map<String, Object> vars; 047 048 public JexlConditionParser(final Map vars) { 049 if (vars == null) { 050 throw new IllegalArgumentException("vars"); 051 } 052 this.vars = vars; 053 } 054 055 public JexlConditionParser() { 056 // Setup the default vars 057 vars = new HashMap<String, Object>(); 058 ParserUtils.addDefaultVariables(vars); 059 } 060 061 /** 062 * Evaluate a condition expression. 063 * 064 * @param expression The condition expression to evaluate; must not be null 065 * @return True if the condition is satisfied 066 * 067 * @throws org.apache.geronimo.system.configuration.condition.ConditionParserException Failed to evaluate condition expression 068 */ 069 public boolean evaluate(final String expression) throws ConditionParserException { 070 if (expression == null) { 071 throw new IllegalArgumentException("Expression must not be null"); 072 } 073 074 // Empty expressions are true 075 if (expression.trim().length() == 0) { 076 log.debug("Expression is empty; skipping evaluation"); 077 078 return true; 079 } 080 081 Object result; 082 try { 083 result = doEvaluate(expression); 084 } 085 catch (Exception e) { 086 throw new ConditionParserException("Failed to evaluate expression: " + expression, e); 087 } 088 089 if (result instanceof Boolean) { 090 return (Boolean) result; 091 } 092 else { 093 throw new ConditionParserException("Expression '" + expression + "' did not evaluate to a boolean value; found: " + result); 094 } 095 } 096 097 private Object doEvaluate(final String expression) throws Exception { 098 assert expression != null; 099 100 boolean debug = log.isDebugEnabled(); 101 102 if (debug) { 103 log.debug("Evaluating expression: " + expression); 104 } 105 106 Expression expr = ExpressionFactory.createExpression(expression); 107 108 JexlContext ctx = JexlHelper.createContext(); 109 ctx.setVars(vars); 110 111 Object result = expr.evaluate(ctx); 112 if (debug) { 113 log.debug("Result: " + result); 114 } 115 116 return result; 117 } 118 }