JDBC PreparedStatement with setObject(int, null) causing SQLException

Detail name	Value
Changelog Number	24032
Type	Bug
Status	Resolved
Affected Versions	Exasol 7.1.0, JDBC 24.0.0
Fix Versions	JDBC 25.2.3
Resolution Date	2025-04-11

Description

When a PreparedStatement is created with multiple parameters and the JDBC driver needs to set the value for a parameter N, it initially creates DummyColumn placeholders for any unset parameters. If an intermediate parameter is set to null, this triggers an SQLException.

Example:

		try {
			// Create JDBC Connection
			// Create Schema and Table with columns C1 DECIMAL(10, 0), C2 VARCHAR(100), C3 DECIMAL(10, 0)

			try (PreparedStatement stmt = conn.prepareStatement("INSERT INTO TABLE (C1, C2, C3) VALUES (?, ?, ?)")) {
				stmt.setInt(1, 1); // Creates column at index 0
				stmt.setInt(3, 1); // Creates column at index 2 and DummyColumn at gap index 1

				stmt.setObject(2, null); // sets null on DummyColumn
				stmt.executeUpdate();
			}
		} catch (SQLException ex) {
			...
		}

Observed Error:

java.sql.SQLException: Invalid parameter data type received from client for parameter 2. Parameter type = 0

Workaround

Using stmt.setObject(2, null, Types.VARCHAR); instead.

Resolution

The issue has been fixed. The driver now correctly detects the DummyColumn and creates the real column even when using setObject(2, null).

Example

stmt.setObject(2, null); // sets null on DummyColumn -> Works now