JSF :: Error In Radio Button Value Reference Not Found

getting the value of the selected radio button. My jsp file has the below code:

<h:selectOneRadio label="Requests" value="#{user.a_request}" layout="pageDirection">
<td ><f:selectItem itemLabel="Forward Request to A" itemValue="A"/></td>
<td ><f:selectItem itemLabel="Forward Request to B" itemValue="B"/></td>
</h:selectOneRadio>

Any my java bean has:

package test;
import java.io.Serializable;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;
import java.util.Map;

[code]...

in the value of the radio button "{#user.a_request}", it is producing an error that the reference "user" is not found.