15.6.3. Security in the user interface

A well-designed interface does not present a user with options they are not permitted to use. Seam Security allows conditional rendering of page sections or individual controls based on user privileges, using the same EL expressions that are used for component security.
In this section, we will go through some examples of interface security. Say we have a login form that we want rendered only if the user is not already logged in. We can write the following with the identity.isLoggedIn() property: 
<h:form class="loginForm" rendered="#{not identity.loggedIn}">
If the user is not logged in, the login form will be rendered — very straightforward. Say we also have a menu on this page, and we want some actions to be accessed only by users in the manager role. One way you could write this is the following: 
<h:outputLink action="#{reports.listManagerReports}" 
   rendered="#{s:hasRole('manager')}"> Manager Reports 
</h:outputLink>
This, too, is straightforward — if the user is not a member of the manager role, the outputLink will not be rendered. The rendered attribute can generally be used on the control itself, or on a surrounding <s:div> or <s:span> control.
A more complex example of conditional rendering might be the following situation: say you have a h:dataTable control on a page, and you want to render action links on its records only for users with certain privileges. The s:hasPermission EL function lets us use an object parameter to determine whether the user has the necessary permission for that object. A dataTable with secured links might look like this: 
<h:dataTable value="#{clients}" var="cl">
  <h:column>
    <f:facet name="header">Name</f:facet>
    #{cl.name}
  </h:column>
  <h:column>
    <f:facet name="header">City</f:facet>
    #{cl.city}
  </h:column>
  <h:column>
    <f:facet name="header">Action</f:facet>
    <s:link value="Modify Client" action="#{clientAction.modify}"
            rendered="#{s:hasPermission(cl,'modify')"/>
    <s:link value="Delete Client" action="#{clientAction.delete}"
            rendered="#{s:hasPermission(cl,'delete')"/>
  </h:column>
</h:dataTable>