/*
* Copyright 2010 Alibaba Group Holding Limited.
* All rights reserved.
*
* Licensed 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 com.alibaba.citrus.expr.jexl;
import static com.alibaba.citrus.util.Assert.*;
import org.apache.commons.jexl2.Expression;
import org.apache.commons.jexl2.JexlContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.alibaba.citrus.expr.ExpressionContext;
import com.alibaba.citrus.expr.support.ExpressionSupport;
/**
* ����һ��jexl���ʽ��
*
* @author Michael Zhou
*/
public class JexlExpression extends ExpressionSupport {
private static final Logger log = LoggerFactory.getLogger(JexlExpression.class);
private Expression expression;
/**
* ����һ��Jexl���ʽ��
*
* @param expr jexl���ʽ����
*/
public JexlExpression(Expression expr) {
this.expression = expr;
}
/**
* ȡ�ñ��ʽ�ַ�����ʾ��
*
* @return ���ʽ�ַ�����ʾ
*/
public String getExpressionText() {
return expression.getExpression();
}
/**
* ��ָ�����������м�����ʽ��
*
* @param context <code>ExpressionContext</code>������
* @return ���ʽ�ļ�����
*/
public Object evaluate(ExpressionContext context) {
try {
JexlContext jexlContext = new JexlContextAdapter(context);
if (log.isDebugEnabled()) {
log.debug("Evaluating EL: " + expression.getExpression());
}
Object value = expression.evaluate(jexlContext);
if (log.isDebugEnabled()) {
log.debug("value of expression: " + value);
}
return value;
} catch (Exception e) {
log.warn("Caught exception evaluating: " + expression + ". Reason: " + e, e);
return null;
}
}
/**
* ��<code>ExpressionContext</code>���䵽<code>JexlContext</code>��
*/
private static class JexlContextAdapter implements JexlContext {
private ExpressionContext expressionContext;
public JexlContextAdapter(ExpressionContext expressionContext) {
this.expressionContext = assertNotNull(expressionContext, "expressionContext");
}
public Object get(String key) {
return expressionContext.get(key);
}
public void set(String key, Object value) {
expressionContext.put(key, value);
}
public boolean has(String key) {
return expressionContext.get(key) != null;
}
}
}