As I recall, Java 1.3.1 supports only
JDBC 2.0 which doesn't provide a mechanism for creating a clob, only reading them.
Unfortunately you will have to use oracle.sql.CLOB.getCharacterOutputStream() to get a writer that will allow you to write to your clob.
Java 1.4 includes JDBC 3.0 which does provide Clob.setCharacterStream().