SQLException: ERROR: column "evtjson" is of type json but expression is of type character varying
Hint: You will need to rewrite or cast the expression.
Take the hint, literally. You never did show the SQL but usually the least complex way to solve this is to indeed transfer the data as a string/text and then instruction PostgreSQL to convert (i.e., cast) it to json.
SELECT (?)::json; <-- that ? parameter is seen as text; then you convert it. The parentheses should be optional but I use them to emphasize the point.
