A problem encountered during a small example of javabean+jsp

Question

About a problem encountered during a small example of javabean jsp
There is no connection error in the database, and index.jsp can also be displayed. . .
Please help the newbies to answer~~... ...under the guidance of my little brother...^ ^
Thank you very much ~! !

Jump to login.jsp
Why is a null pointer error reported?

sql table


The code is as follows:

index.jsp

login.jsp

UserService.java

User.java

Conn.java

Answer 1

user is empty, username and password cannot be obtained

In this case, you have written the logic of data submission in jsp, but the background does not receive it. You can write it in action or controller

User u = new User();
u.setUsername(request.getParameter("username"));
u.setPassword(request.getParameter("password"));

调用service并传参就ok了

Answer 2

Personally, I think a checkInput should be added first to determine whether it is the data passed by the login form? Otherwise, it will be null at the beginning when the page is rendered?

1. String name=request.getPamareter("name");
   if(name=="loin"){//It should be login

............
}