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PostgreSQL's JDBC driver fully supports calling PostgreSQL stored functions.
Example 31-4. Calling a built in stored function
This example shows how to call a PostgreSQL built in function, upper, which simply converts the supplied string argument to uppercase.
// Turn transactions off.
con.setAutoCommit(false);
// Procedure call.
CallableStatement upperProc = con.prepareCall("{ ? = call upper( ? ) }");
upperProc.registerOutParameter(1, Types.VARCHAR);
upperProc.setString(2, "lowercase to uppercase");
upperProc.execute();
String upperCased = upperProc.getString(1);
upperProc.close();
CallableStatement Interface All the considerations that apply
for Statement
and PreparedStatement apply
for CallableStatement but in addition
you must also consider one extra restriction:
You can only call a stored function from within a transaction.
ResultSet from a stored functionPostgreSQL's stored function can return results by means of a refcursor value. A refcursor.
As an extension to JDBC,
the PostgreSQL JDBC driver can
return refcursor values
as ResultSet values.
Example 31-5. Getting refcursor values from a function
When calling a function that returns
a refcursor you must cast the return type
of getObject to
a ResultSet
// Turn transactions off.
con.setAutoCommit(false);
// Procedure call.
CallableStatement proc = con.prepareCall("{ ? = call doquery ( ? ) }");
proc.registerOutParameter(1, Types.Other);
proc.setInt(2, -1);
proc.execute();
ResultSet results = (ResultSet) proc.getObject(1);
while (results.next()) {
// do something with the results...
}
results.close();
proc.close();It is also possible to treat the refcursor
return value as a distinct type in itself. The JDBC driver
provides
the org.postgresql.PGRefCursorResultSet
class for this purpose.
Example 31-6. Treating refcursor as a distinct type
con.setAutoCommit(false);
CallableStatement proc = con.prepareCall("{ ? = call doquery ( ? ) }");
proc.registerOutParameter(1, Types.Other);
proc.setInt(2, 0);
org.postgresql.PGRefCursorResultSet refcurs
= (PGRefCursorResultSet) con.getObject(1);
String cursorName = refcurs.getRefCursor();
proc.close();