Scriptlet variable doesn't get evaluated inside an attribute of a custom JSP tag

Question

I am trying to have a JavaScript function called when I click a link. This JavaScript function is definied in an attribute of a JSP tag and I am trying to pass a scriptlet variable to the function. However, it doesn't get evaluated. The relevant part of the code is:

<span>
  <mysecurity:secure_link id='<%="editButton_"+commentUUID%>' entitlement="" 
    actionOnClick="editComment('<%= commentUUID %>');return false;"
    isSurroundedByBrackets="true" enableTitle="" disableLink="<%=disableLink%>">
    <span style="color:#0033BB; font:8pt arial;">
      <bean:message key="button.edit" />
    </span>
   </mysecurity:secure_link>
</span>

IE8 mentions a JavaScript error in the bottom left corner. When I right click and view source, the generated HTML is:

onclick="editComment('<%= commentUUID %>');return false;"

So, the <%=commentUUID%> is not been evaluated in the actionOnClick attribute, but it's successfully been evaluated in id attribute.

How is this caused and how can I fix it?

What happens when you click the link? Is there an error message displayed in either the Firebug or WebKit developer tools' console? Or does nothing happen? — tommytwoeyes
It was a comment. Not an answer to your question. Without seeing the generated HTML code it's hard to say what's broken - but javascript: inside onclick="..." is always unnecessary. — ThiefMaster
@matt: just plain raw javascript. onclick="editComment(...)". The only time you'd use a javascript: pseudourl is in <a href="javascript:...">...</a>. — Marc B
It says error on page in the bottom left corner (I am using IE8) then when I right click and view source, the relevant line is: onclick="editComment('<%= commentUUID %>');return false;" '<%= commentUUID %>' is normally replaced by its string value defined in the jsp normally but it is not — Matt

BalusC BalusC · Accepted Answer · 2011-08-09T20:23:10

I'm not sure whether the <mysecurity:secure_link> is a custom or an existing 3rd party JSP tag library. Modern JSP tags usually do not evaluate legacy scriptlet expressions. You should rather be using EL (Expression Language) instead.

First ensure that commentUUID variable is been stored as an attribute of the page or request scope so that it's available to EL, like as the following example in a preprocessing servlet:

request.setAttribute("commentUUID", commentUUID);

or using another scriptlet in JSP:

<% request.setAttribute("commentUUID", commentUUID); %>

or using JSTL's <c:set> in JSP:

<c:set var="commentUUID"><%=commentUUID%></c:set>

then you can access it as follows in EL:

<mysecurity:secure_link actionOnClick="editComment('${commentUUID}');return false;" />

Scriptlet variable doesn't get evaluated inside an attribute of a custom JSP tag

2 Answers