用weblogic连接池如何读写oracle的CLOB数据，报错

Question

public void insertUser(UserInfoDTO user) throws DataAccessException {
                try {
                        this.con = this.getConnection();
                        final String insertSql = "INSERT INTO USERINFO(USERID,USERName,memo) VALUES(?,?,?)";
                        final String selectSql = "SELECT MEMO FROM USERINFO WHERE USERID = ? FOR UPDATE";
                        final String updateSql = "UPDATE USERINFO SET MEME = ? WHERE USERID = ?";
                        PreparedStatement ps = con.prepareStatement(insertSql);
                        ps.setString(1, user.getUserID());
                        ps.setString(2, user.getUserName());
                        ps.setClob(3, CLOB.empty_lob());
                        ps.executeUpdate();
                        ps.close();                        ps = this.con.prepareStatement(selectSql);
                        ps.setString(1, user.getUserID());
                        ResultSet rs = ps.executeQuery();
                        rs.next();                        CLOB memo = (CLOB) rs.getClob(1);
                        memo.setString(1, user.getMemo());                        ps = this.con.prepareStatement(updateSql);
                        ps.setClob(1, memo);
                        ps.setString(2, user.getUserID());
                        ps.executeUpdate();
                        ps.close();
                        this.con.commit();
                } catch (Exception ex) {
                        throw new DataAccessResourceFailureException(ex.getMessage(), ex);
                } finally {
                        try {
                                if (this.con != null)
                                        this.con.close();
                        } catch (Exception ex) {
                                throw new DataAccessResourceFailureException(ex.getMessage(),
                                                ex);
                        }
                }        }