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package javax.faces.component.visit;
import java.util.AbstractCollection;
import java.util.Collection;
import java.util.Iterator;
import java.util.Set;
import javax.faces.FactoryFinder;
import javax.faces.component.UIComponent;
import javax.faces.context.FacesContext;
/**
*
* A context object that is used to hold
* state relating to performing a component tree visit.
*
*
*
* Component tree visits are initiated by calling {@link
* UIComponent#visitTree}, at which point both a
* {@link VisitContext} and a {@link VisitCallback} must be provided.
*
*
* @see UIComponent#visitTree UIComponent.visitTree()
* @see VisitCallback
*
* @since 2.0
*/
abstract public class VisitContext {
// Design notes: The VisitContext contract could be defined
// as an interface. However, there is the potential that we
// may need to add new methods in the future, so leaving as
// an abstract class in order to have room to grow.
//
// Since we are an abstract class rather than an interface,
// we could provide implementations of of some of the simpler
// methods (eg. getFacesContext() and getHints()) to avoid
// duplicating this code in VisitContext implementations.
// However, doing so would mean that "wrapping" VisitContext
// implementations would be forced to pick up such implementations,
// so going with a pure contract (no implementation).
/**
* This unmodifiable Collection is
* returned by getIdsToVisit() and
* getSubtreeIdsToVisit() in cases where all ids should
* be visited.
* To simplify logic for
* visitTree() implementations, this Collection always
* returns false for isEmpty. All other
* methods throw UnsupportedOperationException.
*
* @since 2.0
*/
// Note: We cannot use Collections.emptyList() as that returns
// a shared instance - we want to unique instance to allow for
// identity tests.
static public final Collection ALL_IDS =
new AbstractCollection() {
@Override
public Iterator iterator() {
throw new UnsupportedOperationException(
"VisitContext.ALL_IDS does not support this operation");
}
@Override
public int size() {
throw new UnsupportedOperationException(
"VisitContext.ALL_IDS does not support this operation");
}
@Override
public boolean isEmpty() {
return false;
}
};
/**
* Returns the FacesContext for the
* current request.
* @since 2.0
*/
abstract public FacesContext getFacesContext();
/**
* Returns the ids of the components
* to visit.
* In the case of a full tree visit,
* this method returns the ALL_IDS collection. Otherwise, if a
* partial visit is beign performed, returns a modifiable collection
* containing the client ids of the components that should be
* visited.
*/
abstract public Collection getIdsToVisit();
/**
* Given a {@link
* javax.faces.component.NamingContainer} component, returns the
* client ids of any components underneath the NamingContainer that
* should be visited.
*
* This method is called by NamingContainer visitTree()
* implementations to determine whether the NamingContainer contains
* components to be visited. In the case where no such components
* exist, the NamingContainer can short-circuit the tree visit and
* avoid descending into child subtrees.
* In addition, iterating components such as UIData may be able
* to use the returned ids to determine which iterated states
* (ie. rows) need to be visited. This allows the visit traversal
* to be contstrained such only those rows that contain visit
* targets need to be traversed.
*
* @param component a NamingContainer component
* @return an unmodifiable Collection containing the client ids of
* any components underneath the NamingContainer that are known to be
* targets of the tree visit. If no such components exist, returns
* an empty Collection. If all components underneath the
* NamingContainer should be visited, returns the
* {@code VisitContext.ALL_IDS} collection.
* @throws IllegalArgumentException if {@code component} is not
* an instance of NamingContainer
*/
abstract public Collection getSubtreeIdsToVisit(UIComponent component);
/**
* Called by {@link UIComponent#visitTree UIComponent.visitTree()}
* to visit a single component.
*
* @param component the component to visit
* @param callback the VisitCallback to call
* @return a VisitResult value that indicates whether to continue
* visiting the component's subtree, skip visiting the component's
* subtree or abort the visit altogether.
*/
abstract public VisitResult invokeVisitCallback(UIComponent component,
VisitCallback callback);
/**
* Returns hints that influence the behavior of the tree visit.
*
* Interested parties, such as
* {@link UIComponent#visitTree UIComponent.visitTree()} implementations,
* may check to see whether a particular hint is present by calling
* {@code VisitContext.getHints().contains()}, passing in one of the
* hints defined by {@link VisitHint}.
*
* @return a non-empty, unmodifiable collection of VisitHints
*/
abstract public Set getHints();
/**
* Returns a VisitContext instance that is initialized with the
* specified ids and hintsfor use with {@link
* UIComponent#visitTree}.
*
* @param context the FacesContext for the current request
* @param ids the client ids of the components to visit. If null,
* all components will be visited.
* @param hints the VisitHints to apply to the visit. If
* null, no hints are applied.
* @return a VisitContext instance that is initialized with the
* specified ids and hints.
*/
public static VisitContext createVisitContext(FacesContext context,
Collection ids,
Set hints) {
VisitContextFactory factory = (VisitContextFactory)
FactoryFinder.getFactory(FactoryFinder.VISIT_CONTEXT_FACTORY);
return factory.getVisitContext(context, ids, hints);
}
/**
* Creates a VisitContext instance for use with
* {@link UIComponent#visitTree UIComponent.visitTree()}.
* This method can be used to obtain a VisitContext instance
* when all components should be visited with the default
* visit hints.
* @param context the FacesContext for the current request
* @return a VisitContext instance
*/
public static VisitContext createVisitContext(FacesContext context) {
return createVisitContext(context, null, null);
}
}