Question

I’m working on a JSP where I need to call methods on object that come from a Bean. The previous version of the page does not use JSTL and it works properly. My new version has a set up like this:

<jsp:useBean id='pageBean' scope='request' type='com.epicentric.page.website.PageBean' /> <c:set var='pageDividers' value='<%= pageBean.getPageDividers() %>' /> <c:set var='numColumns' value='${pageDividers.size()}' /> 

The variable pageDividers is a List object.

I’m encountering this issue: when I ask for pageDivider‘s size, an exception is thrown. I know this is a simple JTSL error — what am I doing wrong?

The error message is:

The function size must be used with a prefix when a default namespace is not specified

How do I correctly access or call the methods of my pageDividers object?

Answer 1

When using the dot operator for property access in JSTL, ${pageDividers.size} (no () needed) results in a call to a method named getSize().
Since java.util.List offers a method called size() (rather than getSize()) you won’t be able to access the list length by using that code.

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In order to access to a list size, JSTL offers the fn:length function, used like

${fn:length(pageDividers)} 

Note that in order to use the fn namespace, you should declare it as follows

<%@ taglib uri='http://java.sun.com/jsp/jstl/functions' prefix='fn' %> 

In addition, the same function can be used with any collection type, and with Strings too.