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The [ActionResultInterpreter|http://saffron.caret.cam.ac.uk/cgi-bin/cvsweb/rep/RSFUtil/src/uk/org/ponder/rsf/processor/ActionResultInterpreter.java] (ARI) marks the last stage of POST processing, and an important site for application configuration. It inspects the result of the just-concluded Action and computes the next view to be shown.

The full code for ActionResultInterpreter appears here:

{{{

public interface ActionResultInterpreter {

public ARIResult interpretActionResult(ViewParameters incoming, Object result);

}

}}}

with the ARIResult as follows:

{{{

public class ARIResult {

public AnyViewParameters resultingview;

public String propagatebeans;

}

}}}

The Object {{result}} is the return value from the reflective invocation of the [method binding|EL], which is intended to be a String. The result may simply be null, possibly because the actual return type of the method is {{void}} rather than {{String}}.

The ActionResultInterpreter effectively embodies the "web flow" or "site map" of the application (in conjunction with the plain links that are rendered into pages), and we expect "interesting" implementations of this interface using a variety of technologies (for example, [Spring Web Flow|http://www.theserverside.com/articles/article.tss?l=SpringWebFlow] or [Cocoon|http://cocoon.apache.org/].

Right now RSF supplies two alternative infrastructures for implementing ARIs, used to make users coming from two competing/neighbouring technologies ([JSF] and [SWF]) feel more at home. You may use the [FlowLite] system, which defines a lightweight clone of the Spring Web Flow FSA-style flow map scheme, with all transitions in a flow linked in a single flow definition XML file, as seen in the [Number Guessing sample|NumberGuessing]. Alternatively you may use the JSFNavActionResultInterpreter which applies JSF-style rule-based semantics, whereby each POST initiates a one-step flow. This also allows the rule definitions to be bundled with the view definition, leading to self-contained views such as in the [Hibernate CookBook|HibernateCookBook]. However, the ARI interface is so light that the door is open for any number of other techniques.

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[#1] Note that since ThreadErrorState uses an old-fashioned ThreadLocal access pattern, in order to minimise penalties to its use below the [BeanLine], we may as well continue using it from there, all the design penalties have already been paid.