In reference to issue #24 , while consuming null value message from Kafka, the output json should contains

"value": null

currently it is outputing

"value": ""

It could be convenient for doing a data backup or a data transfer between topics. A current workaround is to use jq tool to replace the empty string by null, but it only works if the topic is not supposed to contain empty string
Here the jq

jq -c '{partition:.partition,key:.key,value:(if (.value|length) > 0 then .value else null end)}'