Transformer not accepting Message as the input

Question

I've just begun migrating the java DSL we've used for our project from Java 7 to 8, and i'm facing weird issues. I have a success channel for an ExpressionEvaluatingRequestHandlerAdvice which is expecting an AdviceMessage . In the Java 7 version, it was working fine with:

.transform(new GenericTransformer<AdviceMessage, Message<?>>() {
    @Override
    public Message<?> transform(AdviceMessage source) {
        return source.getInputMessage();
    }
})

but when i convert it to Java 8:

.<AdviceMessage, Message<?>>transform(advice -> advice.getInputMessage())

it gives me an exception:

org.springframework.integration.handler.advice.ExpressionEvaluatingRequestHandlerAdvice$ MessageHandlingExpressionEvaluatingAdviceException: Handler Failed; nested exception is org.springframework.integration.transformer.MessageTransformationException: Failed to transform Message; nested exception is org.springframework.messaging.MessageHandlingException: nested exception is java.lang.ClassCastException: java.lang.Boolean cannot be cast to org.springframework.integration.message.AdviceMessage

Boolean was the result of the success expression i had given so it turns out that the method is expecting the payload and not letting me get hold of the whole message.

When i tried to change other parts of the flow the error consistently started popping up wherever I've tried to put a generic argument expecting a Message<?> instead of the payload of the message.

I can't figure out if i'm doing any of the Java 8 syntax wrong, or the error is due to something else entirely, since the Java 7 version is working perfectly.

I couldn't find any Java DSL examples on the web where there were generic casts to Message instead of the payload, so i don't even know if it's supposed to work.

Thanks for the help.

Answer 1

That the problem of genetics erasure. Since that one becomes just an Object , we don't have choice unless try to extract only payload from the message, because this is most common use-case.

To fix your concern you have to use overload .transform() version with the AdviceMesaage.class as a first argument.

That way we know the expected type and can make the method invocation with the proper argument call.