If I have a servlet called LoginServlet that accepts username and password and I display this form in the doGet() method, when I submit this form I want doGet() of LoginServlet to be called again so that it can check with database . But won't the username and password be null this time? What must I do to prevent it from becoming null the second time I call doGet()?
I'm not sure I'm understanding this right. Wouldn't it be null the first time and not the second time? It sounds to me like the first time, you display the form (and the userid/password are not known yet.) In general, if you want to remember attributes, you can store them in the session.
You can also pass it back and forth in in the request using request.setAttribute in the servlet and request.getAttribute in the JSP. You'll need the RequestDispatcher object to forward the request back to the JSP though. One thing I do not understand is the use of the GET in the form which will subsequently call the doGet method of the servlet. Choosing GET as the method in the form will append all of the data to the URL and it will show up in the URL bar of your browser. This doen't seem like something you'd want to do for a login screen. I'd use POST instead.
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