Spark SQL function json_object_keys
can be used to return an array of the outmost JSON object's keys. The input can be a valid JSON string too.
Code snippet
spark-sql> select json_object_keys('{}');
[]
spark-sql> select json_object_keys('{"key": "value"}');
["key"]
spark-sql> select json_object_keys('{"key1":"value1","key2":{"key3":"value3", "key4":"value4"}}');
["key1","key2"]
infoThis function is only available from Spark 3.1.0.