protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String name = request.getParameter("name");
        String password =  request.getParameter("password");
        if(null == name || null == password || name.trim().equals("") || password.equals(""))
        {
            request.setAttribute("message", "请输入用户名和密码");
            request.getRequestDispatcher("/index.jsp").forward(request, response);
        }
        
        if(name.equals(password))
        {
            request.setAttribute("name", name);
            request.getRequestDispatcher("/welcome.jsp").forward(request, response);
            
        }else
        {
            request.setAttribute("message", "请输入正确的用户名和密码");
            request.getRequestDispatcher("/index.jsp").forward(request, response);
        }
    }

if(null == name && name.trim().equals("")  )
        {
            request.setAttribute("message", "请输入用户名和密码");
            request.getRequestDispatcher("/index.jsp").forward(request, response);
        }
if(null == password && password.equals("")){

}

------解决方案--------------------

转发了方法其实并没有结束，如果想结束方法还得在后面加return关键字。