Store Json field as String in Elastic search?

As of today ElasticSearch 7.12 "enabled" is now "index".

So mapping should be like this:

"json_field": {
    "type": "object",
    "index" : false
},

Solution

Set "enabled": false for the field.

curl -X PUT "localhost:9200/{{INDEX-NAME}}/_mapping/doc" -H 'Content-Type: application/json' -d'
{
    "properties" : {
      "json_field" : {
        "type" : "object",
        "enabled": false
      }
    }
}

Note: This cannot be applied to the existing field. Either pass it in mapping during the creation of index or you can always create a new field.

Explanation

The enabled setting, which can be applied only to the top-level mapping definition and to object fields, causes Elasticsearch to skip parsing of the contents of the field entirely. The JSON can still be retrieved from the _source field, but it is not searchable or stored in any other way:

Ref: Elasticsearch Docs

Finally got it, if you want to store JSON as a string, without analyzing it, the mapping should be like this

"json_field": {
    "type": "object",
    "enabled" : false
},

The enabled flag allows to disable parsing and indexing a named object completely. This is handy when a portion of the JSON document contains an arbitrary JSON which should not be indexed, nor added to the mapping.

Update - From ES version 7.12 "enabled" has been changed to "index".