7.3. Page parameters

A Faces request (a JSF form submission) encapsulates both an action (a method binding) and parameters (input value bindings). A page action can also require parameters.
Since non-Faces (GET) requests can be bookmarked, page parameters are passed as human-readable request parameters.
You can use page parameters with or without an action method.

7.3.1. Mapping request parameters to the model

Seam lets us provide a value binding that maps a named request parameter to an attribute of a model object. 
<pages> 
  <page view-id="/hello.jsp" action="#{helloWorld.sayHello}"> 
    <param name="firstName" value="#{person.firstName}"/> 
    <param name="lastName" value="#{person.lastName}"/> 
  </page> 
</pages>
The <param> declaration is bidirectional, as with value bindings for JSF input:
  • When a non-Faces (GET) request for the view ID occurs, Seam sets the value of the named request parameter to the model object, after performing appropriate type conversions.
  • Any <s:link> or <s:button> includes the request parameter transparently. The parameter value is determined by evaluating the value binding during the render phase (when the <s:link> is rendered).
  • Any navigation rule with a <redirect/> to the view ID includes the request parameter transparently. The parameter value is determined by evaluating the value binding at the end of the invoke application phase.
  • The value is transparently propagated with any JSF form submission for the page with the given view ID. This means that view parameters behave like PAGE-scoped context variables for Faces requests.
However we arrive at /hello.jsp, the value of the model attribute referenced in the value binding is held in memory, without the need for a conversation (or other server-side state).