Selenium Webdriver [Java] [gecko]：如何将字符串传递给Alert中的输入字段

I have an online Web Application where there is a product listed which have a View button. On clicking the View button an alert is shown. The Alert have four (4) fields as: Alert Text, An Input Text field, OK button & Cancel button. The Alert text reads as "The Alert Text is :Product is out of Stock ! Please enter your Email Id".I have an online Web Application where there is