从同一个JSP中的onclick（）文本字段获取值参数

I'm writing on a Web Application (Crowdfunding Platform - Student Project) and my Problem is a JSP page where the user can back a Project. I have a form field for the User where he can type in the amount of his donation and after this the same JSP should display the associated rewards. Finally he can submit the action to the Servlet.I'm writing on a Web Application (Crowdfunding