How to keep only some message headers and remove all others?

Question

How do I keep only specific headers but get rid of all other headers?

I'm trying to remove irrelevant headers that were set by an upstream HttpRequestHandlingMessagingGateway.

I tried specifying a handle() function that returns a new message containing only the headers I'm interested in but it does not seem to work. The log message contains a bunch of HTTP headers that were set from the upstream HttpRequestHandlingMessagingGateway.

IntegrationFlows.from(myChannel())
                // Strip off the HTTP specific headers
                .handle((payload, headers) -> MessageBuilder
                        .withPayload(payload)
                        .setHeader("myCustomHeader1", headers.get("myCustomHeader1", String.class))
                        .setHeader("myCustomHeader2", headers.get("myCustomHeader2", String.class))
                        .build()
                )
                .log()

I see there is a HeaderFilter but it requires you to know the name of the headers you want to remove. In my case I only want to keep 2 custom headers and remove everything else.

Answer 1

class HeaderStripper {

    public Message<?> strip(Message<?> msg) {
        return org.springframework.integration.support.MessageBuilder.withPayload(msg.getPayload())
                .setHeader("foo", msg.getHeaders().get("foo"))
                .setHeader("bar", msg.getHeaders().get("bar"))
                .build();
    }

}

and then

.transform(new HeaderStripper())