JavaWeb 原生Ajax

        

    用户名:"text" name="username" onblur="checkUsername(this.value);"/>
        "nameTipMsg" style="font-size: 12px;">

    密码:"password" name="password">





serlvet 3.0


@WebServlet(name = "CheckUsernameAction",urlPatterns = "/checkusername.do")
public class CheckUsernameAction extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.sendRedirect("text/html;charset睿共享=UTF-8");
        PrintWriter out = resp.getWriter();
        //获取用户名
        String username = req.getParameter("username");

        //连接数据库验证用户名是否存在
        if("admin".equals(username)){
            //用户名不可用
            out.print("用户名被注册");
        }else{
            out.print("用户名可注册");

        }

        //响应信息给浏览器
    }

}