Javascript and Jsp page

This might be very simple one but i am not understanding where i am doing wrong. I have a form which has three links, namely LogIn,SignUp and ForgotPassword. I used javascript document..action to set action for these links using a simple switch case. while Singup and ForgotPassword refer to singup.jsp and ForgotPassword.jsp respectively, LogIn link refers to a servlet. And i used url-pattern given in web.xml file as its target. when i run it gives error upon clicking on sigin. Any idea what's going wrong?

<script type="text/javascript">
    function redirect(tid)
    {
      switch(tid)开发者_如何学运维
      {
        case "a":
        {
            if(document.form.Username.value=='')
            {
                alert("Enter your username");
                return false;
            }
            if(document.form.Password.value=='')
            {
                alert("Enter your password");
                return false;
            }
             document.form.action="check" //check is the urlpattern defined for checkUser servlet
        }
        break;
        case "b":
            document.form.action="Signup.jsp"
            break;

        case "c":
            document.form.action="Forgotpassword.jsp"
            break;
     }
    }
</script>

Try this:

document.forms[0].action = 'Forgotpassword.jsp';

As per the comment on the question:

The error is HTTP POST method is not supported by this URL

The servlet which is listening on the URL does not have the doPost() method overridden. Apparently you're using a <form method="post"> to submit to a servlet which has only doGet() implemented. You need to rename the doGet() method to doPost().

Please note that this has nothing to do with the JavaScript code which you posted in the question.