Kafka - Schema

You can use an schema, for example, to:

• serialize an object (POJO)
• and deserialize it back into an object.

An Avro schema defines the data structure in a JSON format.

{"namespace": "example.avro",
 "type": "record",
 "name": "user",
 "fields": [
     {"name": "name", "type": "string"},
     {"name": "favorite_number",  "type": "int"}
 ]
}

where:

• Kafka - (Record|Message)

Schema management is done through the schema registry service

Example made with sqlite getting started

curl -X GET http://localhost:8081/subjects

["test-sqlite-jdbc-accounts-value"]

List all schema versions registered under a subject. Example made with sqlite getting started

curl -X GET http://localhost:8081/subjects/subjectName/versions

# Example
curl -X GET http://localhost:8081/subjects/test-sqlite-jdbc-accounts-value/versions

[1,2]

Fetch version n of the schema registered under the subject. Example made with sqlite getting started

curl -s -X GET http://localhost:8081/subjects/subjectName/versions/n | jq .

# Example
curl -s -X GET http://localhost:8081/subjects/test-sqlite-jdbc-accounts-value/versions/1 | jq .

{                                                                                                                                                                                                          
  "subject": "test-sqlite-jdbc-accounts-value",                                                                                                                                                            
  "version": 1,                                                                                                                                                                                            
  "id": 1,                                                                                                                                                                                                 
  "schema": "{\"type\":\"record\",\"name\":\"accounts\",\"fields\":[{\"name\":\"id\",\"type\":\"long\"},{\"name\":\"name\",\"type\":[\"null\",\"string\"],\"default\":null}],\"connect.name\":\"accounts\"}"                                                                                                                                                                                                          
}

The schema property properly indented is:

{
	"type ": "record",
	"name":"accounts",
	"fields": [{
			"name":"id",
			"type":"long"
		}, {
			"name":"name",
			"type": ["null","string"],
			"default": null
		}
	],
	"connect.name":"accounts"
}

# Deletes all schema versions registered under the subject "Kafka-value"
$ curl -X DELETE http://localhost:8081/subjects/Kafka-value
  [1]

# Deletes version 1 of the schema registered under subject "Kafka-value"
$ curl -X DELETE http://localhost:8081/subjects/Kafka-value/versions/1
  1

# Deletes the most recently registered schema under subject "Kafka-value"
$ curl -X DELETE http://localhost:8081/subjects/Kafka-value/versions/latest
  1

• org/apache/kafka/connect/data/Schema