/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.geronimo.system.configuration.condition;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;
import org.apache.commons.jexl.Expression;
import org.apache.commons.jexl.ExpressionFactory;
import org.apache.commons.jexl.JexlContext;
import org.apache.commons.jexl.JexlHelper;
import org.apache.commons.jexl.context.HashMapContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Provides a simple facility to evaluate condition expressions using the
* <a href="http://jakarta.apache.org/commons/jexl">Jexl</a> language.
*
* <p>
* This class is thread-safe.
* </p>
*
* @version $Rev: 653740 $ $Date: 2008-05-06 18:44:18 +0800 (Tue, 06 May 2008) $
*/
public class JexlConditionParser
implements ConditionParser
{
private static final Logger log = LoggerFactory.getLogger(JexlConditionParser.class);
private final Map<String, Object> vars;
public JexlConditionParser(final Map vars) {
if (vars == null) {
throw new IllegalArgumentException("vars");
}
this.vars = vars;
}
public JexlConditionParser() {
// Setup the default vars
vars = new HashMap<String, Object>();
ParserUtils.addDefaultVariables(vars);
}
/**
* Evaluate a condition expression.
*
* @param expression The condition expression to evaluate; must not be null
* @return True if the condition is satisfied
*
* @throws org.apache.geronimo.system.configuration.condition.ConditionParserException Failed to evaluate condition expression
*/
public boolean evaluate(final String expression) throws ConditionParserException {
if (expression == null) {
throw new IllegalArgumentException("Expression must not be null");
}
// Empty expressions are true
if (expression.trim().length() == 0) {
log.debug("Expression is empty; skipping evaluation");
return true;
}
Object result;
try {
result = doEvaluate(expression);
}
catch (Exception e) {
throw new ConditionParserException("Failed to evaluate expression: " + expression, e);
}
if (result instanceof Boolean) {
return (Boolean) result;
}
else {
throw new ConditionParserException("Expression '" + expression + "' did not evaluate to a boolean value; found: " + result);
}
}
private Object doEvaluate(final String expression) throws Exception {
assert expression != null;
log.debug("Evaluating expression: {}", expression);
Expression expr = ExpressionFactory.createExpression(expression);
JexlContext ctx = JexlHelper.createContext();
ctx.setVars(vars);
Object result = expr.evaluate(ctx);
log.debug("Result: {}", result);
return result;
}
}