Setting NULL value using af:setPropertyListener in ADF

 Usually we come across common requirement to set value of session scope or pageFlowScope variable to NULL on click of adf button or  af:commandLink to do this you can af:setPropertyListener inside af:commandLink as below and use EL as #{null}

<af:commandLink text="Clear">

            <af:setPropertyListener  from="#{null}"

                                                  to="#{sessionScope.userName}"

                                                   type="action"/>

</af:commandLink>

in above case i am setting userName to null.