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.spi;
018    
019    /**
020     * Access to a repository of Message IDs to implement the
021     * <a href="http://camel.apache.org/idempotent-consumer.html">Idempotent Consumer</a> pattern.
022     * <p/>
023     * The <tt>add</tt> and <tt>contains</tt> methods is operating according to the {@link java.util.Set} contract.
024     *
025     * @version $Revision: 738604 $
026     */
027    public interface IdempotentRepository<E> {
028    
029        /**
030         * Adds the key to the repository.
031         *
032         * @param key the key of the message for duplicate test
033         * @return <tt>true</tt> if this repository did <b>not</b> already contain the specified element
034         */
035        boolean add(E key);
036    
037        /**
038         * Returns <tt>true</tt> if this repository contains the specified element.
039         *
040         * @param key the key of the message
041         * @return <tt>true</tt> if this repository contains the specified element
042         */
043        boolean contains(E key);
044    }