How can I Insert JSON object into Postgres using Java preparedStatement?

This behaviour is quite annoying since JSON strings are accepted without problems when used as literal strings in SQL commands.

There is a already an issue for this in the postgres driver Github repository (even if the problem seems the be the serverside processing).

Besides using a cast (see answer of @a_horse_with_no_name) in the sql string, the issue author offers two additional solutions:

1. Use a parameter stringtype=unspecified in the JDBC connection URL/options.

This tells PostgreSQL that all text or varchar parameters are actually of unknown type, letting it infer their types more freely.

2. Wrap the parameter in a org.postgresql.util.PGobject:

 PGobject jsonObject = new PGobject(); jsonObject.setType("json"); jsonObject.setValue(yourJsonString); pstmt.setObject(11, jsonObject);

You can do it like this and you just need the json string:

Change the query to:

String query = "INSERT INTO table (json_field) VALUES (to_json(?::json))"

And set the parameter as a String.

pStmt.setString(1, json);

Passing the JSON as a String is the right approach, but as the error message tells you, you need to cast the parameter in the INSERT statement to a JSON value:

insert into the_table   (.., evtjson, ..) values    (.., cast(? as json), ..)

Then you can use pStmt.setString(11, dtlRec.toString()) to pass the value