CODEWITHSUNDEEP
javajavascriptjspjakarta-eenetbeans
MindBrain
MindBrain

Reputation: 7768

Unable to view alert in the browser window

I have written a code to display an error message if the user login fails. The servlet code is as follows:

HttpSession session = request.getSession(true);


/*User class is a Java bean with an isValid attribute*/
  User user= new User(); 
  if (!user.isValid()) {
         request.setAttribute("errorMessage"," Invalid Parameters!");
         request.getRequestDispatcher("RegistrationPage.jsp").forward(request, response);
  }



// RegistrationPage.jsp file code snippet is below


<script>
function loginFailure() {
           System.out.println("Invalid parameters");
           if(request.getParameter("errorMessage") != null) {
              alert("<%= request.getParameter("errorMessage") %>");        
           }

</script>

<body onload="loginFailure()">
</body>

I cannot understand why the page is not displaying the alert message when there is a failure in the login. It does go into the method for loginFailure and to the alert function as well.

Upvotes: 0

Views: 331

Answers (2)

MindBrain
MindBrain

Reputation: 7768

Scriptlet and javascript to display this message:

<%
            String message = (String) request.getAttribute("errorMessage");
            if (message != null) {
            %> 
              <script>
                   alert('<%=message%>');
              </script> 
           <%
            }else{

            %>
            <script>
                 alert("Login Successfull");

            </script>
        <%       
            }
        %>

Upvotes: 0

Steve Schneider
Steve Schneider

Reputation: 402

First, as @PM 77-1 says, you need to do getAttribute() not getParameter(). Also, don't you want that System.out to execute only if the conditional is true? But the larger problem is that you're mixing up your Java and JavaScript. Your conditional if(request.getParameter("errorMessage") != null), presumably meant to be executed server-side as Java code, isn't within scriptlet tags, so the JavaScript interpreter will try to execute it and fail. Seems like what you want to be doing is this:

<script>
function loginFailure() {<%
           if(request.getParameter("errorMessage") != null) {
               System.out.println("Invalid parameters"); 
               %>
               alert("<%= request.getAttribute("errorMessage") %>");
               <%      
           }%>
</script>

That's the simplest fix. Although you don't really want to be mingling server-side and client-side code to the extent you are either (i.e., putting any Java code within a JavaScript function). Better to define a var errorMessage outside the function, like var errorMessage="<%=request.getAttribute("errorMessage")==null?"":request.getAttribute("errorMessage").toString()%>" and then use a JavaScript conditional (not Java, as it seems you were trying to do) which alerts the error message only if its length is greater than zero.

Upvotes: 1

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