Inbound Channel Adapters: Polling Multiple Servers and Directories

Starting with version 5.0.7, the RotatingServerAdvice is available; when configured as a poller advice, the inbound adapters can poll multiple servers and directories. Configure the advice and add it to the poller’s advice chain as normal. A DelegatingSessionFactory is used to select the server see Delegating Session Factory for more information. The advice configuration consists of a list of RotationPolicy.KeyDirectory objects.spring-doc.cn

Example

@Bean
public RotatingServerAdvice advice() {
    List<RotationPolicy.KeyDirectory> keyDirectories = new ArrayList<>();
    keyDirectories.add(new RotationPolicy.KeyDirectory("one", "foo"));
    keyDirectories.add(new RotationPolicy.KeyDirectory("one", "bar"));
    keyDirectories.add(new RotationPolicy.KeyDirectory("two", "baz"));
    keyDirectories.add(new RotationPolicy.KeyDirectory("two", "qux"));
    keyDirectories.add(new RotationPolicy.KeyDirectory("three", "fiz"));
    keyDirectories.add(new RotationPolicy.KeyDirectory("three", "buz"));
    return new RotatingServerAdvice(delegatingSf(), keyDirectories);
}

This advice will poll directory foo on server one until no new files exist then move to directory bar and then directory baz on server two, etc.spring-doc.cn

This default behavior can be modified with the fair constructor arg:spring-doc.cn

fair

@Bean
public RotatingServerAdvice advice() {
    ...
    return new RotatingServerAdvice(delegatingSf(), keyDirectories, true);
}

In this case, the advice will move to the next server/directory regardless of whether the previous poll returned a file.spring-doc.cn

Alternatively, you can provide your own RotationPolicy to reconfigure the message source as needed:spring-doc.cn

policy

public interface RotationPolicy {

    void beforeReceive(MessageSource<?> source);

    void afterReceive(boolean messageReceived, MessageSource<?> source);

}

andspring-doc.cn

custom

@Bean
public RotatingServerAdvice advice() {
    return new RotatingServerAdvice(myRotationPolicy());
}

The local-filename-generator-expression attribute (localFilenameGeneratorExpression on the synchronizer) can now contain the #remoteDirectory variable. This allows files retrieved from different directories to be downloaded to similar directories locally:spring-doc.cn

@Bean
public IntegrationFlow flow() {
    return IntegrationFlow.from(Ftp.inboundAdapter(sf())
                    .filter(new FtpPersistentAcceptOnceFileListFilter(new SimpleMetadataStore(), "rotate"))
                    .localDirectory(new File(tmpDir))
                    .localFilenameExpression("#remoteDirectory + T(java.io.File).separator + #root")
                    .remoteDirectory("."),
                e -> e.poller(Pollers.fixedDelay(1).advice(advice())))
            .channel(MessageChannels.queue("files"))
            .get();
}

Do not configure a TaskExecutor on the poller when using this advice; see Conditional Pollers for Message Sources for more information.