I have seen couple of postings on this I have similar situation here with this exception java.sql.SQLException: ORA-01722: invalid number

I am inserting the values into a table in the using a procedure calling that in the jsp page using callable statement.prepareCall(?,?.......)
One of the out parameters is varchar2(10) which is tmp_Quote_number and it is number(10) , not null in the database table.

i am getting this eception
strSQL: SELECT quote_name,country_code,currenc
y_code1,currency_code2,industry_code,quote_status, customer_code,original_quote_number,TO_CHAR(quote_ effective_d
ate,'DD-MON-YYYY'),NVL(total_units, 0),contract_term, TRIM(billing_frequency),TRIM(environment_code),env ironmen
t_adj,blended_zone_pct,billing_adj,NVL(term_disc,0 ),NVL(volume_disc,0),NVL(discretionary_disc,0), iswotquote, c
ustomer_number, created_by, warning_message FROM spt_quote_header_temp WHERE TEMP_QUOTE_NUMBER = 'null' , Excep
tion: java.sql.SQLException: ORA-01722: invalid number