我试过这个：

PreparedStatement stmt = cnt.prepareStatement(
        "select OUT from QRTZ_JOBEXEC where EXEC_ID=? "
            + "for update",ResultSet.TYPE_FORWARD_ONLY,ResultSet.CONCUR_UPDATABLE);
try {
    stmt.setLong(1,id);
    ResultSet rs = stmt.executeQuery();
    if (rs.next()) {
        Clob clob = rs.getClob(1);
        long len = clob.length();
        Writer writer = clob.setCharacterStream(len+1);
        try {
            PrintWriter out = new PrintWriter(writer);
            out.println(line);
            out.close();
        } finally {
            writer.close();
        }
        rs.updateClob(1,clob);
        rs.updateRow();
    }
    rs.close();
} finally {
    stmt.close();
}

但是我在调​​用setCharacterStream时遇到“不支持的功能”异常.