core/camel-api/src/main/java/org/apache/camel/RecipientList.java

/*
 * 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;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * Indicates that this method is to be used as a 
 * <a href="http://camel.apache.org/recipient-list.html">Dynamic Recipient List</a> routing the incoming message
 * to one or more endpoints.
 *
 * When a message {@link org.apache.camel.Exchange} is received from an {@link org.apache.camel.Endpoint} then the
 * <a href="http://camel.apache.org/bean-integration.html">Bean Integration</a>
 * mechanism is used to map the incoming {@link org.apache.camel.Message} to the method parameters.
 *
 * The return value of the method is then converted to either a {@link java.util.Collection} or array of objects where each
 * element is converted to an {@link Endpoint} or a {@link String}, or if it is not a collection/array then it is converted
 * to an {@link Endpoint} or {@link String}.
 *
 * Then for each endpoint or URI the message is forwarded a separate copy.
 */
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Target({ElementType.FIELD, ElementType.METHOD, ElementType.CONSTRUCTOR })
public @interface RecipientList {

    /**
     * Delimiter used if the Expression returned multiple endpoints. Can be turned off using the value <tt>false</tt>.
     * <p/>
     * The default value is ,
     */
    String delimiter() default ",";

    /**
     * If enabled then sending messages to the recipients occurs concurrently.
     * Note the caller thread will still wait until all messages has been fully processed, before it continues.
     * Its only the sending and processing the replies from the recipients which happens concurrently.
     */
    boolean parallelProcessing() default false;

    /**
     * If enabled then the aggregate method on AggregationStrategy can be called concurrently.
     * Notice that this would require the implementation of AggregationStrategy to be implemented as thread-safe.
     * By default this is false meaning that Camel synchronizes the call to the aggregate method.
     * Though in some use-cases this can be used to archive higher performance when the AggregationStrategy is implemented as thread-safe.
     */
    boolean parallelAggregate() default false;

    /**
     * Will now stop further processing if an exception or failure occurred during processing of an
     * {@link org.apache.camel.Exchange} and the caused exception will be thrown.
     * <p/>
     * Will also stop if processing the exchange failed (has a fault message) or an exception
     * was thrown and handled by the error handler (such as using onException). In all situations
     * the recipient list will stop further processing. This is the same behavior as in pipeline, which
     * is used by the routing engine.
     * <p/>
     * The default behavior is to <b>not</b> stop but continue processing till the end
     */
    boolean stopOnException() default false;

    /**
     * If enabled, unwind exceptions occurring at aggregation time to the error handler when parallelProcessing is used.
     * Currently, aggregation time exceptions do not stop the route processing when parallelProcessing is used.
     * Enabling this option allows to work around this behavior.
     *
     * The default value is <code>false</code> for the sake of backward compatibility.
     */
    boolean stopOnAggregateException() default false;

    /**
     * If enabled then Camel will process replies out-of-order, eg in the order they come back.
     * If disabled, Camel will process replies in the same order as defined by the recipient list.
     */
    boolean streaming() default false;

    /**
     * Whether to ignore the invalidate endpoint exception when try to create a producer with that endpoint
     */
    boolean ignoreInvalidEndpoints() default false;

    /**
     * Sets a reference to the AggregationStrategy to be used to assemble the replies from the recipients, into a single outgoing message from the RecipientList.
     * By default Camel will use the last reply as the outgoing message. You can also use a POJO as the AggregationStrategy
     */
    String strategyRef() default "";

    /**
     * Refers to a custom Thread Pool to be used for parallel processing.
     * Notice if you set this option, then parallel processing is automatic implied, and you do not have to enable that option as well.
     */
    String executorServiceRef() default "";

    /**
     * Sets a total timeout specified in millis, when using parallel processing.
     * If the Recipient List hasn't been able to send and process all replies within the given timeframe,
     * then the timeout triggers and the Recipient List breaks out and continues.
     * Notice if you provide a TimeoutAwareAggregationStrategy then the timeout method is invoked before breaking out.
     * If the timeout is reached with running tasks still remaining, certain tasks for which it is difficult for Camel
     * to shut down in a graceful manner may continue to run. So use this option with a bit of care.
     */
    long timeout() default 0;

    /**
     * Uses the {@link Processor} when preparing the {@link org.apache.camel.Exchange} to be send.
     * This can be used to deep-clone messages that should be send, or any custom logic needed before
     * the exchange is send.
     */
    String onPrepareRef() default "";

    /**
     * Shares the {@link org.apache.camel.spi.UnitOfWork} with the parent and each of the sub messages.
     * Recipient List will by default not share unit of work between the parent exchange and each recipient exchange.
     * This means each sub exchange has its own individual unit of work.
     */
    @Deprecated
    boolean shareUnitOfWork() default false;
}