java.sql.SQLException: Field 'supplier_id' doesn't have a default value

The error is self explanatory. Your column supplier_id does not have a default value. So during insertion, mysql cannot figure out what to insert in the column supplier_id. You can do either of the three things :-
1. Add a default value to the column supplier_id Using -

ALTER TABLE `xxx` ALTER `supplier_id` SET DEFAULT NULL

2. Supply some value to the supplier_id column during insertion.
3. Add an auto increment to the column and add a primary key to it using the code :-

ALTER TABLE `xxx` CHANGE `supplier_id` `supplier_id` INT(10)AUTO_INCREMENT PRIMARY KEY;

To solve this, either supply a value for supplier_id when you do the INSERT, or make the column nullable in the DB.