Spring Cloud Streams not setting the kafka key in the message? -

the story this. have kafka broker , particular object (which jsonify send through topics) has id want use key.

currently i'm using 'partitionkeyextractorclass' configuration set class extracts id , returns key.

it looks this:

def extractkey(message<?> message) {     log.info('extracting key message')     string id = new jsonslurper().parsetext(new string(message.payload)).properties.id     log.info("got = ${id}")      return id } 

my actual problem when browse message on topic consumerrecord holds message says key null...

is bug? doing wrong? documentation on doesn't go further this.

look, mixing partition key.

currently kafkamessagechannelbinder doesn't provide option determine key against message.

only existing functionality can use powerfully kafkaheaders.message_key:

    object messagekey = this.messagekeyexpression != null             ? this.messagekeyexpression.getvalue(this.evaluationcontext, message)             : message.getheaders().get(kafkaheaders.message_key); 

so, before output message should calculate key , place header.