JSP: <%@ taglib uri="/struts-tags" prefix="s" %> Action class: import java.util.List; public class TestAction { public String execute() { return "success"; } public void setFoo(final List foo) { for (final Integer item : foo) { System.out.println(item); } } } struts.xml part: /test.jsp If you press the button, this will throw a big ClassCastException at: for (final Integer item : foo)