Retrieve converter attribute expression from UIViewParameter

Question

I need to create a dependent converter for a view-param which JSF has no built in solution for.

In this example bar is dependent on foo.

<f:viewParam name="foo" value="#{bean.foo}" converter="#{appScopeBean.fooConverter}"/>
<f:viewParam name="bar" value="#{bean.bar}" converter="#{bean.barConverter}"/>

In @PostConstruct the converted value for bean.foo is not yet available, but i could manually retrieve the request parameter bar and the Converter by performing el lookup.

@PostConstruct
public void init()
{
    // mimic UIViewParameter behavior

    // grab request parameter manually
    final String fooId = context.getExternalContext().getRequestParameterMap().get("foo");

    // grab converter manually
    final Converter fooConverter = context.getApplication().evaluateExpressionGet(context,
        "#{appScopeBean.fooConverter}", Converter.class);

    final Foo foo = fooConverter.getAsObject(context, null, fooId);

    // create Bar converter dependent on Foo
}

Now i tried to obtain the converter by resolving the UIViewParameter, but its converter instance is null since not yet set by JSF lifecycle (why? if converter scope is broader it should be safe). So i want to obtain the el-expression to lookup the converter to do something like (to reduce the need to hardcode it as above DRY):

@PostConstruct
public void init()
{
    // mimic UIViewParameter behavior

    final UIViewParameter fooViewParam = FacesContextUtils.getViewParam(context, "foo");

    // final Converter fooConverter = fooViewParam.getConverter(); is null

    // pseudo code
    final Converter fooConverter = context.getApplication().evaluateExpressionGet(context,
        fooViewParam.getConverterExpression(), Converter.class);

    final Foo foo = fooConverter.getAsObject(context, null, fooId);

    // create Bar converter dependent on Foo
}

JSF should handle support for dependent converters like some iterative life-cycle bean event that is invoked after each UIViewParameter converter instantiation.