Retrieve message based on the payload

[ttruong]

The API allows me to deal either with Spring's message or the payload itself:

public class SomeEndpoint {
Message<SomePayloadClass> doSomething(AnotherPayloadClass payload)
{
...
}
}

What if I deal only with the payload and later I realize I need the message (e.g. the get some header information)?

I am concerned that when using SI over time there will be lots of classes and I do not want to refactor them only the deal with messages instead of payloads.

Is there a convenient way of getting the message for a certain payload?

Thanks Tai

[Mark Fisher]

If you need to access the Message, you can change the signature to accept the Message itself (return type does not necessarily need to change):

Message<SomePayloadClass> doSomething(Message message) {...}

Alternatively, if you need to access specific header values, you can add additional parameters with the @Header annotation:

Message<SomePayloadClass> doSomething(AnotherPayloadClass payload, @Header("x") String x, @Header("y") int y) {...}

[ttruong]

The @Header annotation is very useful. But imagine the following Type Hierarchy:

Class A
Class B and C extends from A; where B overrides:
PayloadClass doSomething(AnotherPayloadClass inputPayload)

In case for class C I realize that I need some header information. It would be ugly to refactor all classes to use the header annotation as a parameter.

I do also not know what happens at runtime with overloaded methods like in the C class:

//new method including header annotation along with the unchange method from B
PayloadClass doSomething(AnotherPayloadClass inputPayload, @Header("x") String headerX)

Both approaches aren't that nice (especially when dealing with legacy code). Maybe the best practice is to always deal with Spring's Message class for a parameter instead of the payload? Which isn't the best solution either (dependency to Spring, payload must be explicitely retrieved) .

[ttruong]

Maybe there should something like MesseageHeadersAware (with a set/getHeaders() - similar to the ApplicationContextAware).

Meaning: I just need to implement the interface and when the message handler calls the bean it attaches the header.

Would that be a proper solution?