Gibt es in Spring Integration Java DSL eine Möglichkeit, einen vorhandenen Nachrichtenkopf zu ändern?

Ich implementiere einen Download-Wiederholungsmechanismus mit SI Java DSL neu und möchte einen Nachrichtenkopf erhöhen, der die Download-Versuche enthält, wenn ein Fehler auftritt, bevor die Nachricht basierend auf der Anzahl der Versuche im Vergleich zu einem Grenzwert weitergeleitet wird.

Ich habe das Routing gut funktioniert, basierend auf den in SI enthaltenen RouterTests. Mit HeaderEnrichers kann ich leicht einen Header hinzufügen, aber ich sehe keine Möglichkeit, einen vorhandenen Header zu ändern.

Vielen Dan

/**
 * Unit test of {@link RetryRouter}.
 * 
 * Based on {@link RouterTests#testMethodInvokingRouter2()}.
 */
@ContextConfiguration
@RunWith(SpringJUnit4ClassRunner.class)
@DirtiesContext
public class RetryRouterTests {

    /** Failed download attempts are sent to this channel to be routed by {@link ContextConfiguration#failedDownloadRouting( ) } */
    @Autowired
    @Qualifier("failed")
    private MessageChannel failed;

    /** Retry attempts for failed downloads are sent to this channel by {@link ContextConfiguration#failedDownloadRouting( ) }*/
    @Autowired
    @Qualifier("retry-channel")
    private PollableChannel retryChannel;

    /** Failed download attempts which will not be retried, are sent to this channel by {@link ContextConfiguration#failedDownloadRouting( ) }*/
    @Autowired
    @Qualifier("exhausted-channel")
    private PollableChannel exhaustedChannel;

    /**
     * Unit test of {@link ContextConfiguration#failedDownloadRouting( ) } and {@link RetryRouter}.
     */
    @Test
    public void retryRouting() {

        final int limit = 2;

        for ( int attempt = 0 ; attempt <= limit + 1 ; attempt++ ){

            this.failed.send( failed( attempt, limit) );

            if ( attempt < limit){

                assertEquals( payload( attempt ) , this.retryChannel.receive( ).getPayload( ) );
                assertNull(this.exhaustedChannel.receive( 0 ) );

            }else{

                assertEquals( payload( attempt ) , this.exhaustedChannel.receive( ).getPayload( ) );
                assertNotNull( this.exhaustedChannel.receive( ).getPayload( ) );
            }
        }

    }

    private Message<String> failed( int retry , int limit ) {

        return MessageBuilder
            .withPayload(  payload( retry ) )
            .setHeader("retries", new AtomicInteger( retry ) )
            .setHeader("limit", limit)
            .build();
    }

    private String payload (int retry){
        return "retry attempt "+retry;
    }


    @Configuration
    @EnableIntegration
    public static class ContextConfiguration {

        @Bean
        public MessageChannel loggerChannel() {
            return MessageChannels.direct().get();
        }

        @Bean(name = "retry-channel")
        public MessageChannel retryChannel() {
            return new QueueChannel();
        }

        @Bean(name = "exhausted-channel")
        public MessageChannel exhaustedChannel() {
            return new QueueChannel();
        }


        /**
         * Decides if a failed download attempt can be retried or not, based upon the number of attempts already made 
         * and the limit to the number of attempts that may be made. Logic is in {@link RetryRouter}.
         * <p>
         * The number of download attempts already made is provided as a header {@link #attempts} from the connector doing the download, 
         * and the limit to the number of attempts is another header {@link #retryLimit} which is originally setup as
         * a header by {@link DownloadDispatcher} from retry configuration.
         * <p>
         * Messages for failed download attempts are listened to on channel {@link #failed}. 
         * Retry attempts are routed to {@link #retryChannel()}
         *  
         * @return
         */
        @Bean
        public IntegrationFlow failedDownloadRouting() {

            return IntegrationFlows.from( "failed" )

                .handle( "headers.retries.getAndIncrement()" )
                .handle( logMessage ( "failed" ) )
                .route(new RetryRouter())
                .get();
        }

        /**
         * Decides if a failed download attempt can be retried or not, based upon the number of attempts already made 
         * and the limit to the number of attempts that may be made. 
         * <p>
         */
        private static class RetryRouter {

            @Router
            public String routeByHeader(@Header("retries") AtomicInteger attempts , @Header("limit") Integer limit) {

                if (attempts.intValue() < limit.intValue()){
                    return "retry-channel";
                }
                return "exhausted-channel";
            }

            /** This method is not used but is required by Spring Integration otherwise application context doesn't load because of
             * {@code Caused by: java.lang.IllegalArgumentException: Target object of type 
             * [class org.springframework.integration.dsl.test.routers.RetryRouterTests$RetryRouter] has no eligible methods for handling Messages.}
             * 
             * @throws UnsupportedOperationException if called
             */
            @SuppressWarnings("unused")
            public String routeMessage(Message<?> message) {

                throw new UnsupportedOperationException( "should not be used." );
            }
        }
    }