JSP simple Exercise-page redirection

In JSP programming, it is often to redirect the page, such as in the page program to add a judgment statement that satisfies the condition to go to a page, does not meet the conditions to another page.

The following is a simple example:

<%@ page contenttype= "text/html; charset=gb2312"%>
In this procedure, a form is declared, the data is submitted to this page, the form is submitted when the option to change the dropdown box is changed, and in the program, the page is redirected with the Sendredirect () method of the response object after it receives the address to be turned in the submitted form. In the program to determine whether the received parameters are empty, because the data submitted to this page, when the form data is not submitted, the data of the corresponding data will be empty, the page is not redirected.