JSF-使用Primefaces RowEditEvent时如何获取新旧值？

我有一个包含2列（名称和描述）的数据表，当有人更新一行并单击触发该execBacking.update方法的选中标记时，我想更新数据库。

在这种方法中，我可以通过强制转换获得新值event.getObject()，但是我又如何才能获得旧值呢？名称是我的主键，因此我需要旧值来知道要更新数据库中的哪一行。

xhtml页面

  <p:ajax event="rowEdit" listener="#{execBacking.update}" update=":execForm:execMessages" /> 

  <p:column headerText="Name">
    <p:cellEditor>
        <f:facet name="output">
            <h:outputText value="#{exec.name}" />
        </f:facet>
        <f:facet name="input">
            <h:inputText value="#{exec.name}" />
        </f:facet>
    </p:cellEditor>
  </p:column>

  <p:column headerText="Description">
    <p:cellEditor>
        <f:facet name="output">
            <h:outputText value="#{exec.description}" />
        </f:facet>
        <f:facet name="input">
            <h:inputText value="#{exec.description}" />
        </f:facet>
    </p:cellEditor>
  </p:column>

  <p:column headerText="Actions">
    <p:rowEditor />
    <p:commandLink styleClass="ui-icon ui-icon-trash" type="submit" actionListener="#{execBacking.delete}" update=":execForm:execMessages" >
            <f:attribute name="execName" value="#{exec.name}" />
        </p:commandLink>
  </p:column>
</p:dataTable>

支持豆

public void update(RowEditEvent event) {

        Dao dao = new Dao(ds);
        Exec exec = (Exec) event.getObject();
        System.out.println("name = "+exec.getName());  //New name
        System.out.println("desc = "+exec.getDescription());  //New desc
        try {
            // If the new exec was updated successfully
            if(dao.updateExec(accessBacking.getUsername(), null, exec.getName(), exec.getDescription())) {
                FacesContext.getCurrentInstance().addMessage("growl", new FacesMessage(FacesMessage.SEVERITY_INFO, "Success", "Exec Updated Successfully!"));
            } else {
                FacesContext.getCurrentInstance().addMessage("messages", new FacesMessage(FacesMessage.SEVERITY_ERROR, "Error", "Error Updating Exec!"));
            }
        } catch (Exception e) {
            FacesContext.getCurrentInstance().addMessage("messages", new FacesMessage(FacesMessage.SEVERITY_ERROR, "Error", e.getMessage()));
        }
    }