i have a problem with the datatable component. I want to create a datatable with checkbox like a multiple selection example on primefaces showcase. This is the code:

```
<p:dataTable id="table_cats" value="#{fooBean.catsList}" var="cat" selectionMode="single"   selection="#{fooBean.selectedCatsToDelete}">
<p:column selectionMode="multiple">
    <f:facet name="header">Remove</f:facet>
</p:column>
<p:column>
    <f:facet name="header">Cat Name</f:facet>
        <h:outputText value="#{cat.name}" />
    </p:column></p:dataTable>

```

So, the problem is when a select an item. I don't know how to get all the selected items in the table. Can anyone help me with this problem?