[seam-issues] [JBoss JIRA] Created: (SEAMFACES-109) Provide a query API to retrieve components from view metadata

[Dan Allen (JIRA)]

Provide a query API to retrieve components from view metadata
-------------------------------------------------------------

                 Key: SEAMFACES-109
                 URL: https://issues.jboss.org/browse/SEAMFACES-109
             Project: Seam Faces
          Issue Type: Feature Request
          Components: UI Components
    Affects Versions: 3.0.0.CR1
            Reporter: Dan Allen
            Priority: Minor


The ViewMetadata API only provides a method for retrieving the collection of UIViewParameter components. However, this facet can be used for many other components, such as view actions, view restrictions and so forth. Seam Faces should provide a convenient query API for retrieving any type of component.

Here is a proposal:

{code:java}
public class ViewMetadataQuery {
    public <C extends UIComponent> Collection<C> findMetadataComponents(UIViewRoot viewRoot,
            UIComponentFilter<C> componentFilter) { 
        UIComponent metadataFacet = viewRoot.getFacet(UIViewRoot.METADATA_FACET_NAME);
       
        if (metadataFacet == null) {
            return Collections.<C>emptyList();
        }  
        
        Collection<C> matches = new ArrayList<C>();
        for (UIComponent candidate : metadataFacet.getChildren()) {
            if (componentFilter.accepts(candidate)) {
                matches.add((C) candidate);
            } 
        }  
        
        return matches;
    }   
}   
   
public class UIComponentFilter<C extends UIComponent> {
    public abstract boolean accepts(UIComponent candidate);
}
{code}

It would be used as follows:

{code:java}
@Inject
private ViewMetadataQuery query;
...
Collection<UIViewAction> viewActions = query.findMetadataComponents(viewRoot, new UIComponentFilter<UIViewAction>() {
    public boolean accepts(UIComponent candidate) {
        return candidate instanceof UIViewAction;
    }
});
{code}

You can simplify this further by providing a version of the method that accepts a type:

{code:java}
Collection<UIViewAction> viewActions = query.findMetadataComponents(viewRoot, UIViewAction.class);
{code}

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