Question

How to call javascript alert() from JSP method?

Asked by: D_Pawan05

Hi all experts!
Consider following code...
I want a javascript alert() should be displayed on client side when my application executes perticular jsp method.

<%!
public void myMethod()
{
    if(cond1)
    {
        //some code to display javascript alert
        //what should be here?
    }
}
%>

                                  
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Asked On
2009-07-27 at 03:18:40ID24602351
Topics

Java Server Pages (JSP)

,

Java Servlets

Participating Experts
2
Points
20
Comments
3

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Answers

 

by: objectsPosted on 2009-07-27 at 03:22:00ID: 24950058

you can't. jsp is executed on the server, whereas the javascript is executed on the client

 

by: logudotcomPosted on 2009-07-27 at 03:30:23ID: 24950099

try,

<%!
public void myMethod()
{
    if(cond1)
    {
        //some code to display javascript alert
        //what should be here?
        System.out.println("<script language='javascript'>");
        System.out.println("alert('Hello I am from jsp!');");
        System.out.printlin("</script>");
    }
}
%>

                                              
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by: D_Pawan05Posted on 2009-10-01 at 11:11:57ID: 31636043

The answer given is correct but it did not solve my problem perfectly. In my later comments I have asked what to do if I want to call JavaScript alert() from a JSP method. i.e. within <%! ---- %>. Is this possible?

The answer is no. What happens when a JSP function is called, the code within JSP function is executed on server itself. We know JavaScript is client side scripting language. Thus trying to run Client side script from Server is meaningless.

But I have done what I was trying to do. I was trying to display a JavaScript alert to display a message on client browser. I have simply made the return type of the JSP function to String. (I think you have now understood) I have used the String retrieved by JSP function outside the declaration tag <%! %>.

<%!
public String message()
{
if(cond1)
{
return "Cond1";
}
else
{
return "cond2";
}
}
%>
<html>
<head>
</head>
<body onload="alert('<%=message()%>')">
</body>
</html>

However, I am still searching for some efficient ways to do this in more effective manner. May be I need to use AJAX. Anyways this is enough for now. Thank you all for your expert comments.

20120131-EE-VQP-002

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