001    /**
002     *
003     * Licensed to the Apache Software Foundation (ASF) under one or more
004     * contributor license agreements.  See the NOTICE file distributed with
005     * this work for additional information regarding copyright ownership.
006     * The ASF licenses this file to You under the Apache License, Version 2.0
007     * (the "License"); you may not use this file except in compliance with
008     * the License.  You may obtain a copy of the License at
009     *
010     * http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    package org.apache.camel.util;
019    
020    import org.apache.camel.Exchange;
021    import org.apache.camel.Expression;
022    
023    /**
024     * A collection of helper methods for working with expressions.
025     *
026     * @version $Revision: 1.1 $
027     */
028    public class ExpressionHelper {
029    
030        /**
031         * Evaluates the given expression on the exchange as a String value
032         *
033         * @param expression the expression to evaluate
034         * @param exchange the exchange to use to evaluate the expression
035         * @return the result of the evaluation as a string.
036         */
037        public static <E extends Exchange> String evaluateAsString(Expression<E> expression, E exchange) {
038            return evaluateAsType(expression, exchange, String.class);
039        }
040    
041        /**
042         * Evaluates the given expression on the exchange, converting the result to the given type
043         *
044         * @param expression the expression to evaluate
045         * @param exchange the exchange to use to evaluate the expression
046         * @param resultType the type of the result that is required
047         * @return the result of the evaluation as the specified type.
048         */
049        public static <T, E extends Exchange> T evaluateAsType(Expression<E> expression, E exchange, Class<T> resultType) {
050            Object value = expression.evaluate(exchange);
051            return exchange.getContext().getTypeConverter().convertTo(resultType, value);
052        }
053    }