In the tld you write for the tag handler mention the following sub tags in the attribute
<attribute>
<name>xyz</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
import the packagejavax.servlet.jsp.tagext.DynammicAttributes;
add the method
public void setDynamicAttribute(String rui, String localname, Object value) throws JspException
{
<Your Required task>
}
Its better if you SimpleTagSupport class to be extended.