My kafka value is byte array, is not text or json

How to convert logstash to hex string after consuming binary data from kafka

input config

input {
    beats {
        port => 5044
    }

    tcp {
        port => 50000
    }
    kafka {
        bootstrap_servers => "192.168.1.5:9092"
        group_id => "logstash"
        topics => ["xx","xxx"]
        decorate_events => true
        id => "log"
        codec => plain {
            charset => "BINARY"
            ecs_compatibility => "disabled"
        }
    }
}

filter {
    mutate {
        copy => { "[@metadata][kafka]" => "kafka" }
    }
}

output {
    elasticsearch {
        hosts => "elasticsearch:9200"
        user => "logstash_internal"
        password => "${LOGSTASH_INTERNAL_PASSWORD}"
    }
}

But this will get a string of utf-8 encode.

I want to view the message as a hex string in kibana.

So what do I do now to achieve what I want.