ES : Trying to play with default values

defaultvalues.sh

#!/bin/bash

ES='http://localhost:9200'
ESIDX='test3'
ESTYPE='test'

curl -XDELETE $ES/$ESIDX/$ESTYPE

curl -XPUT $ES/$ESIDX/$ESTYPE/_mapping -d '{
  "test" : {
    "properties" : {
      "objectifs" : {"type" : "string", "null_value":"na"}
    }
  }
}'

curl -XPUT $ES/$ESIDX/$ESTYPE/1 -d '{
	"objectifs" : null
}'

curl -XGET $ES/$ESIDX/$ESTYPE/1?pretty=true