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.camel;
018    
019    /**
020     * An <a href="http://activemq.apache.org/camel/expression.html">expression</a>
021     * provides a plugin strategy for evaluating expressions on a message exchange to support things like
022     * <a href="http://activemq.apache.org/camel/scripting-languages.html">scripting languages</a>,
023     * <a href="http://activemq.apache.org/camel/xquery.html">XQuery</a>
024     * or <a href="http://activemq.apache.org/camel/sql.html">SQL</a> as well
025     * as any arbitrary Java expression.
026     *
027     *
028     * @version $Revision: 630591 $
029     */
030    public interface Expression<E extends Exchange> {
031    
032        /**
033         * Returns the value of the expression on the given exchange
034         *
035         * @param exchange the message exchange on which to evaluate the expression
036         * @return the value of the expression
037         */
038        Object evaluate(E exchange);
039    }