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Incoming Metadata Injection

Experimental

Metadata injection is an experimental feature.

When using reactive messaging, Message flow in your system. Each message has a payload but can also contain metadata, as explained in Messages, Payload, Metadata.

You can inject the incoming message metadata as a parameter depending on the method signature. Only methods receiving the payload as a parameter can also receive the metadata. For example, @Incoming("in") void consume(String s) can also receive the metadata using the following signature: @Incoming("in") void consume(String s, MyMetadata m). Note that the payload must be the first parameter.

The metadata can be injected using the class of the metadata to inject. In this case, the method is invoked with null if the metadata is missing. You can also inject the metadata using Optional<MetadataClass>, which would be empty if the incoming message does not contain metadata of type MetadataClass.

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@Incoming("in")
@Outgoing("out")
public String process(String payload, MyMetadata metadata) {
    // ...
    return payload.toUpperCase();
}

@Incoming("in")
@Outgoing("out")
public Uni<String> process2(String payload, MyMetadata metadata) {
    // ...
    return Uni.createFrom().item(payload.toUpperCase());
}

// ...
@Incoming("in")
public void consume(String payload, Optional<MyMetadata> metadata, Period metadata2) {
    // ...
}

@Incoming("in")
public CompletionStage<Void> consume2(String payload, Optional<MyMetadata> metadata, Period metadata2) {
    // ...
    return CompletableFuture.completedFuture(null);
}