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package javax.faces.view;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;
import javax.faces.component.UIComponent;
import javax.faces.component.UIImportConstants;
import javax.faces.component.UIViewAction;
import javax.faces.component.UIViewParameter;
import javax.faces.component.UIViewRoot;
import javax.faces.context.FacesContext;
/**
* ViewMetadata is
* reponsible for extracting and providing view parameter metadata from
* VDL views. Because {@link ViewDeclarationLanguage#getViewMetadata}
* is required to return null for JSP views and
* non-null for views authored in Facelets for JSF 2, this
* specification only applys to Facelets for JSF 2.
*
* @since 2.0
*/
public abstract class ViewMetadata {
/**
* Get the view id
*
* @return the view ID for which this ViewMetadata instance
* was created
*/
public abstract String getViewId();
/**
* Creates a new {@link UIViewRoot}
* containing only view parameter metadata. The processing of
* building this UIViewRoot with metadata should not
* cause any events to be published to the application. The
* implementation must call {@link FacesContext#setProcessingEvents}
* passing false as the argument, at the beginning of
* the method, and pass true to the same method at the
* end. The implementation must ensure that this happens regardless
* of ant exceptions that may be thrown.
*
*
* Take note a compliant implementation has to ensure that:
*
*
* -
* the new UIViewRoot must be set as the FacesContext's viewRoot
* before applying the tag handlers, restoring the old FacesContext
* in a finally block.
*
* -
* The contents of the current UIViewRoot's ViewMap must be copied
* to the ViewMap of the new UIViewRoot before applying the tag handlers.
*
* -
* The {@link UIImportConstants} must be processed after applying the tag handlers.
*
*
*
* @param context the {@link FacesContext} for the current request
* @return a UIViewRoot containing only view parameter metadata
* (if any)
*/
public abstract UIViewRoot createMetadataView(FacesContext context);
/**
* Utility method to extract view
* metadata from the provided {@link UIViewRoot}.
*
* @param root the {@link UIViewRoot} from which the metadata will
* be extracted.
*
* @return a Collection of {@link UIViewParameter}
* instances. If the view has no metadata, the collection will be
* empty.
*/
public static Collection getViewParameters(UIViewRoot root) {
return getMetadataChildren(root, UIViewParameter.class);
}
/**
* Utility method to extract view
* metadata from the provided {@link UIViewRoot}.
*
* @param root the {@link UIViewRoot} from which the metadata will
* be extracted.
*
* @return a Collection of {@link UIViewAction}
* instances. If the view has no metadata, the collection will be
* empty.
*/
public static Collection getViewActions(UIViewRoot root) {
return getMetadataChildren(root, UIViewAction.class);
}
/**
* Utility method to extract view metadata from the provided {@link UIViewRoot}.
*
* @param root The {@link UIViewRoot} from which the metadata will be extracted.
*
* @return A Collection of {@link UIImportConstants} instances.
* If the view has no metadata, the collection will be empty.
*/
public static Collection getImportConstants(UIViewRoot root) {
return getMetadataChildren(root, UIImportConstants.class);
}
/**
* Utility method to determine if the
* the provided {@link UIViewRoot} has metadata. The default implementation will
* return true if the provided {@code UIViewRoot} has a facet
* named {@link UIViewRoot#METADATA_FACET_NAME} and that facet has children.
* It will return false otherwise.
*
* @param root the {@link UIViewRoot} from which the metadata will
* be extracted from
*
* @return true if the view has metadata, false otherwise.
*/
public static boolean hasMetadata(UIViewRoot root) {
return getMetadataFacet(root).map(m -> m.getChildCount() > 0).orElse(false);
}
@SuppressWarnings("unchecked")
private static List getMetadataChildren(UIViewRoot root, Class type) {
return (List) getMetadataFacet(root).map(m -> m.getChildren()).orElseGet(Collections::emptyList)
.stream().filter(c -> type.isInstance(c)).collect(Collectors.toList());
}
private static Optional getMetadataFacet(UIViewRoot root) {
return Optional.ofNullable(root.getFacet(UIViewRoot.METADATA_FACET_NAME));
}
}