document missing exception while updating an index in elasticsearch via java api

I am trying to update a value in my index via java api using UpdateRequest which accepts three arguments.

• Index
• document
• id

Question - I know what my index name is but i am not sure what value should be passed in document and id field.

SAMPLE DATA

{   
"took": 2,  
 "timed_out": false,   "_shards": {      "total": 5,      "successful": 5,      "failed": 0   },
   "hits": {
      "total": 1,
      "max_score": 0.94064164,
      "hits": [
         {
            "_index": "ticketdump",
            "_type": "event",
            "_id": "AVefK2vFmf0chKzzBkzy",
            "_score": 0.94064164,
            "_source": {
               "clientversion": "123465",
               "queue": "test,test",
               "vertical": "test",
               "troubleshooting": "test",
               "reason": "test",
               "status": "test",
               "ticketversion": "1132465",
               "apuid": 1,
               "golive": "2014-07-14",
               "clientname": "test",
               "message": "test",
               "product": "test",
               "clientid": 1,
               "createddatetime": "2016-05-03 09:43:48",
               "area": "test",
               "developmentfix": "test",
               "actiontaken": "test",
               "categoryname": "test",
               "parentcategory": "test",
               "problemdef": "test",
               "ticketid": 1
            }
         }
      ]
   }
}

I tried to pass _source object but it gave document missing error.Maybe I am missing the concept?

JAVA CODE

UpdateRequest updateRequest = new UpdateRequest(
  "ticketdump",
  js.getJSONObject("hits")
    .getJSONArray("hits")
    .getJSONObject(0)
    .getJSONObject("_source")
    .toString(),
  "1"
).script(new Script("ctx._source.message = \"bhavik\""));
client.update(updateRequest).get();