How can I Insert JSON object into Postgres using Java preparedStatement?
I’m struggling to insert a JSON object into my postgres v9.4 DB. I have defined the column called "evtjson" as type json
(not jsonb
).
I am trying to use a prepared statement in Java (jdk1.8) to insert a Json object (built using JEE javax.json libraries) into the column, but I keep running into SQLException errors.
I create the JSON object using:
JsonObject mbrLogRec = Json.createObjectBuilder().build();
…
mbrLogRec = Json.createObjectBuilder()
.add("New MbrID", newId)
.build();
Then I pass this object as a parameter to another method to write it to the DB using a prepared statement. (along with several other fields) As:
pStmt.setObject(11, dtlRec);
Using this method, I receive the following error:
org.postgresql.util.PSQLException: No hstore extension installed. at org.postgresql.jdbc.PgPreparedStatement.setMap(PgPreparedStatement.java:553) at org.postgresql.jdbc.PgPreparedStatement.setObject(PgPreparedStatement.java:1036)
I have also tried:
pStmt.setString(11, dtlRec.toString());
pStmt.setObject(11, dtlRec.toString());
Which produce a different error:
Event JSON: {"New MbrID":29}
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.
But, at least this tells me that the DB is recognizing the column as type JSON. I did try installing the hstore extension, but it then told me that it was not an hstore object.
OracleDocs shows a number of various methods to set the parameter value in the preparedStatement, but I'd rather not try them all if someone knows the answer. (http://docs.oracle.com/javase/8/docs/api/java/sql/PreparedStatement.html) These also reference an additional parameter, SQLType, but I can't find any reference to these.
Should I try setAsciiStream
? CharacterStream
? CLOB?
Solution 1:
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:
- 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.
- Wrap the parameter in a
org.postgresql.util.PGobject
:
PGobject jsonObject = new PGobject();
jsonObject.setType("json");
jsonObject.setValue(yourJsonString);
pstmt.setObject(11, jsonObject);
Solution 2:
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);