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.processor;
018    
019    import org.apache.camel.Exchange;
020    
021    /**
022     * An advice (before and after) to execute cross cutting functionality in the Camel routing engine.
023     * <p/>
024     * The Camel routing engine will execute the {@link #before(org.apache.camel.Exchange)} and
025     * {@link #after(org.apache.camel.Exchange, Object)} methods during routing in correct order.
026     *
027     * @param <T>
028     * @see CamelInternalProcessor
029     */
030    public interface CamelInternalProcessorAdvice<T> {
031    
032        /**
033         * Callback executed before processing a step in the route.
034         *
035         * @param exchange  the current exchange
036         * @return any state to keep and provide as data to the {@link #after(org.apache.camel.Exchange, Object)} method, or use <tt>null</tt> for no state.
037         * @throws Exception is thrown if error during the call.
038         */
039        T before(Exchange exchange) throws Exception;
040    
041        /**
042         * Callback executed after processing a step in the route.
043         *
044         * @param exchange  the current exchange
045         * @param data      the state, if any, returned in the {@link #before(org.apache.camel.Exchange)} method.
046         * @throws Exception is thrown if error during the call.
047         */
048        void after(Exchange exchange, T data) throws Exception;
049    }