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The Core Camel Java DSL based router
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/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.camel.spi;

import org.apache.camel.Service;

/**
 * Access to a repository of Message IDs to implement the
 * Idempotent Consumer pattern.
 * 
 * The add and contains methods is operating according to the {@link java.util.Set} contract.
 * 

 * The repository supports eager (default) and non-eager mode.
 * 

 *     eager: calls add and confirm if complete, or remove if failed
 *     non-eager: calls contains and add if complete, or remove if failed
 * 
 * Notice the remove callback, can be configured to be disabled.
 * 
 * Implementations for the idempotent consumer EIP
 * should favor using {@link org.apache.camel.spi.ExchangeIdempotentRepository} instead.
 *
 * @version
 * @see org.apache.camel.spi.ExchangeIdempotentRepository
 */
public interface IdempotentRepository extends Service {

    /**
     * Adds the key to the repository.
     * 

     * Important: Read the class javadoc about eager vs non-eager mode.
     *
     * @param key the key of the message for duplicate test
     * @return true if this repository did not already contain the specified element
     */
    boolean add(E key);

    /**
     * Returns true if this repository contains the specified element.
     * 

     * Important: Read the class javadoc about eager vs non-eager mode.
     *
     * @param key the key of the message
     * @return true if this repository contains the specified element
     */
    boolean contains(E key);

    /**
     * Removes the key from the repository.
     * 

     * Is usually invoked if the exchange failed.
     * 

     * Important: Read the class javadoc about eager vs non-eager mode.
     *
     * @param key the key of the message for duplicate test
     * @return true if the key was removed
     */
    boolean remove(E key);

    /**
     * Confirms the key, after the exchange has been processed successfully.
     * 

     * Important: Read the class javadoc about eager vs non-eager mode.
     *
     * @param key the key of the message for duplicate test
     * @return true if the key was confirmed
     */
    boolean confirm(E key);
    
    /**
     * Clear the repository.
     * 
     * Important: Read the class javadoc about eager vs non-eager mode.
     */
    void clear();

}