FacesContext facesContext = FacesContext.getCurrentInstance();
DataTable dataTable = (DataTable) facesContext.getViewRoot().findComponent("entities");

List<RequestEntity> newList = (List<RequestEntity>)dataTable.getValue();

<p:dataTable id="entities" widgetVar="cellRequest"
    var="entityVar"
    value="#{pmoRequestService.requestList}"
    rowKey="#{entityVar.cdProcess}"
    selection="#{pmoRequestService.selectedRequest}"
    draggableColumns="true" resizableColumns="true" paginator="true"
    editable="true" editMode="cell" rows="17"
    sortMode="multiple" selectionMode="single" >

... Some columns here

<!--this is unique identifier column for each row-->
<p:column headerText="Request Id" width="60"
        sortBy="#{entityVar.cdProcess}" filterBy="#{entityVar.cdProcess}"
        filterMatchMode="contains">
        <h:outputText value="#{entityVar.cdProcess}" />
</p:column>

...Some columns here

</p:dataTable>