Using Source Connector, using string converter produces payload in json while json converter doesn't

Working with Data Connectors & Integrations
1

Hi I’m new to the community and kafka connect.

I’m trying to configure MongoDB source connector as below to produce kafka event message with payload also in json.
For e.g.)

{
    "name": "mongo-native-cdc-test-connector", 
    "config": {
        "name":"mongo-native-cdc-test-connector",
        "connector.class": "com.mongodb.kafka.connect.MongoSourceConnector", 
        "connection.uri":"<connection url>",
        "startup.mode":"latest",
        "output.format.key":"json",
        "output.format.value":"json",
        "key.converter.schema.enabled":false,
        "value.converter.schema.enabled":false,
        "key.converter":"org.apache.kafka.connect.json.JsonConverter",
        "value.converter":"org.apache.kafka.connect.json.JsonConverter"    
    }
  }

However this produces payload in json string such as

{
    "schema": {
        "type": "string",
        "optional": false
    },
    "payload": "{\"_id\": {\"_data\": \"***\"}, \"operationType\": \"insert\", \"clusterTime\": {\"$timestamp\": {\"t\": 1677466433, \"i\": 1}}, \"fullDocument\": {\"_id\": {\"$oid\": \"***\"}, \"a\": \"name12\", \"b\": \"value12\"}, \"ns\": {\"db\": \"***\", \"coll\": \"***\"}, \"documentKey\": {\"a\": \"name12\", \"_id\": {\"$oid\": \"***\"}}}"
}

Weirdly, I found out that when I use String converter for value Converter, it produces the payload in json as follows.


{
    "_id": {
        "_data": "***"
    },
    "operationType": "insert",
    "clusterTime": {
        "$timestamp": {
            "t": 1677811331,
            "i": 1
        }
    },
    "fullDocument": {
        "_id": {
            "$oid": "***"
        },
        "a": "name21",
        "b": "value21"
    },
    "ns": {
        "db": "***",
        "coll": "***"
    },
    "documentKey": {
        "a": "name21",
        "_id": {
            "$oid": "***"
        }
    }

so I was wondering if this is the correct behavior? I assumed that in order to produce json format i need to use jsonConverter and now i’m really confused what’s going on under the hood… or am I missing something…?

Any reply regarding this would be much appreciated! Thanks in advance.