使用 servlet 在登录页面本身显示密码错误消息

Question

I want to display Username or password incorrect message in a particular <div> in the Login page.

Here is my login.html code.

<div class="wrapper">
            <form class="form-signin" method="POST" action="j_security_check">       
                <h2 class="form-signin-heading text-center" id="head">Login</h2>
                <input type="text" class="form-control"  id="txtuser" name="j_username" placeholder="Username" required="required" />
            <input type="password" class="form-control" id="txtuser" name="j_password" placeholder="Password" required="required"/>
            <div id="error"></div>  
                <button class="btn btn-lg btn-default btn-block login1" id="txtuser" type="submit"><span class="glyphicon glyphicon-log-in"></span> Login</button>   
            </form>
</div>

Here is my servlet code

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

  response.setContentType("text/html");
  PrintWriter out = response.getWriter();

  RequestDispatcher rd=request.getRequestDispatcher("/login.html");

  out.println("<script>");
  out.println("document.getElementById('error').innerText=Sorry UserName or Password Error");
  out.println("</script>");

  rd.include(request, response);
}

The message is not displaying in the <div id="error"> in login file

Answer 1

I found an answer.It is working

Here is my JSP

<%
String login_msg=(String)request.getAttribute("error");  
if(login_msg!=null)
out.println("<font color=red size=4px>"+login_msg+"</font>");
%>

Here is my Servlet

request.setAttribute("error","Invalid Username or Password");
RequestDispatcher rd=request.getRequestDispatcher("/login.jsp");            
rd.include(request, response);

Answer 2

Just set the error message in request as an attribute and show the error div if it's not null.

Servlet:

request.setAttribute("error","Invalid Username/password");

Login.jsp:

Use JSTL and EL for accessing request attribute in JSP. You can use<c:if> for testing the error message.

<c:if test="${not empty requestScope.error}">
      <!-- Show the error div with message-->
</c:if>

Use Implicit object requestScope to get the attribute from request scope.

---

If you want to use HTML only then try it. Not a good way but you can create two separate HTML pages for login.html and login_error.html then redirect to login_error.html when there is any error.

request.getRequestDispatcher("/login_error.html");

Answer 3

Try this:

request.getRequestDispatcher("signin.html").include(request, response);
out.println("<script>document.getElementById('error').innerHTML='Sorry UserName or Password'; </script>");

Don't forget to use single-quotes for string.

Answer 4

Simply move

rd.include(request, response);

before your print statements and it should work. It is because you want the script to execute after the div is defined.