A wrapper class for adding external ordering to containers not * implementing the {@link com.enably.tk.data.Container.Ordered} * interface.
* *If the wrapped container is changed directly (that is, not through * the wrapper), the ordering must be updated with the * {@link #updateOrderWrapper()} method.
* * @author IT Mill Ltd. * @version @VERSION@ * @since 3.0 */ public class ContainerOrderedWrapper implements Container.Ordered, Container.ItemSetChangeNotifier, Container.PropertySetChangeNotifier { /** The wrapped container */ private Container container; /** Ordering information, ie. the mapping from Item ID to the next * item ID */ private Hashtable next; /** Reverse ordering information for convenience and performance * reasons. */ private Hashtable prev; /** ID of the first Item in the container. */ private Object first; /** ID of the last Item in the container. */ private Object last; /** Is the wrapped container ordered by itself, ie. does it implement * the Container.Ordered interface by itself? If it does, this class * will use the methods of the underlying container directly. */ private boolean ordered = false; /** Constructs a new ordered wrapper for an existing Container. Works * even if the to-be-wrapped container already implements the * Container.Ordered interface. * * @param toBeWrapped the container whose contents need to be ordered */ public ContainerOrderedWrapper(Container toBeWrapped) { container = toBeWrapped; ordered = container instanceof Container.Ordered; // Check arguments if (container == null) throw new NullPointerException("Null can not be wrapped"); // Create initial order if needed updateOrderWrapper(); } /** Removes the specified Item from the wrapper's internal hierarchy * structure. Note that the Item is not removed from the underlying * Container. * * @param id ID of the Item to be removed from the ordering */ private void removeFromOrderWrapper(Object id) { if (id != null) { Object pid = prev.get(id); Object nid = next.get(id); if (first.equals(id)) first = nid; if (last.equals(id)) first = pid; if (nid != null) prev.put(nid, pid); if (pid != null) next.put(pid, nid); next.remove(id); prev.remove(id); } } /** Adds the specified Item to the last position in the wrapper's * internal ordering. The underlying container is not modified. * * @param id ID of the Item to be added to the ordering */ private void addToOrderWrapper(Object id) { // Add the if to tail if (last != null) { next.put(last, id); prev.put(id, last); last = id; } else { first = last = id; } } /** Adds the specified Item after the specified itemId in the wrapper's * internal ordering. The underlying container is not modified. * Given item id must be in the container, or must be null. * * @param id ID of the Item to be added to the ordering */ private void addToOrderWrapper(Object id, Object previousItemId) { if (last == previousItemId || last == null) addToOrderWrapper(id); else { if (previousItemId == null) { next.put(id, first); prev.put(first, id); first = id; } else { prev.put(id, previousItemId); next.put(id, next.get(previousItemId)); prev.put(next.get(previousItemId), id); next.put(previousItemId, id); } } } /** Updates the wrapper's internal ordering information to include all * Items in the underlying container. If the contents of the wrapped * container change without the wrapper's knowledge, this method needs * to be called to update the ordering information of the Items. */ public void updateOrderWrapper() { if (!ordered) { Collection ids = container.getItemIds(); // Recreate ordering if some parts of it are missing if (next == null || first == null || last == null || prev != null) { first = null; last = null; next = new Hashtable(); prev = new Hashtable(); } // Filter out all the missing items LinkedList l = new LinkedList(next.keySet()); for (Iterator i = l.iterator(); i.hasNext();) { Object id = i.next(); if (!container.containsId(id)) removeFromOrderWrapper(id); } // Add missing items for (Iterator i = ids.iterator(); i.hasNext();) { Object id = i.next(); if (!next.containsKey(id)) addToOrderWrapper(id); } } } /* Gets the first item stored in the ordered container * Don't add a JavaDoc comment here, we use the default documentation * from implemented interface. */ public Object firstItemId() { if (ordered) return ((Container.Ordered) container).firstItemId(); return first; } /* Test if the given item is the first item in the container * Don't add a JavaDoc comment here, we use the default documentation * from implemented interface. */ public boolean isFirstId(Object itemId) { if (ordered) return ((Container.Ordered) container).isFirstId(itemId); return first != null && first.equals(itemId); } /* Test if the given item is the last item in the container * Don't add a JavaDoc comment here, we use the default documentation * from implemented interface. */ public boolean isLastId(Object itemId) { if (ordered) return ((Container.Ordered) container).isLastId(itemId); return last != null && last.equals(itemId); } /* Gets the last item stored in the ordered container * Don't add a JavaDoc comment here, we use the default documentation * from implemented interface. */ public Object lastItemId() { if (ordered) return ((Container.Ordered) container).lastItemId(); return last; } /* Get the item that is next from the specified item. * Don't add a JavaDoc comment here, we use the default documentation * from implemented interface. */ public Object nextItemId(Object itemId) { if (ordered) return ((Container.Ordered) container).nextItemId(itemId); return next.get(itemId); } /* Get the item that is previous from the specified item. * Don't add a JavaDoc comment here, we use the default documentation * from implemented interface. */ public Object prevItemId(Object itemId) { if (ordered) return ((Container.Ordered) container).prevItemId(itemId); return prev.get(itemId); } /** Adds a new Property to all Items in the Container. * * @param propertyId ID of the new Property * @param type Data type of the new Property * @param defaultValue The value all created Properties are * initialized to * @returntrue if the operation succeeded,
* false if not
*/
public boolean addContainerProperty(
Object propertyId,
Class type,
Object defaultValue)
throws UnsupportedOperationException {
return container.addContainerProperty(propertyId, type, defaultValue);
}
/** Creates a new Item into the Container, assigns it an
* automatic ID, and adds it to the ordering.
*
* @return the autogenerated ID of the new Item or null
* if the operation failed
*/
public Object addItem() throws UnsupportedOperationException {
Object id = container.addItem();
if (id != null)
addToOrderWrapper(id);
return id;
}
/** Adds a new Item by its ID to the underlying container and to the
* ordering.
*
* @return the added Item or null if the operation failed
*/
public Item addItem(Object itemId) throws UnsupportedOperationException {
Item item = container.addItem(itemId);
if (item != null)
addToOrderWrapper(itemId);
return item;
}
/** Removes all items from the underlying container and from the
* ordering.
*
* @return true if the operation succeeded,
* false if not
*/
public boolean removeAllItems() throws UnsupportedOperationException {
boolean success = container.removeAllItems();
if (success) {
first = last = null;
next.clear();
prev.clear();
}
return success;
}
/** Removes an Item specified by itemId from the underlying
* container and from the ordering.
*
* @return true if the operation succeeded,
* false if not
*/
public boolean removeItem(Object itemId)
throws UnsupportedOperationException {
boolean success = container.removeItem(itemId);
if (success)
removeFromOrderWrapper(itemId);
return success;
}
/** Removes the specified Property from the underlying container and
* from the ordering. Note that the Property will be removed from all
* Items in the Container.
*
* @param propertyId ID of the Property to remove
* @return true if the operation succeeded,
* false if not
*/
public boolean removeContainerProperty(Object propertyId)
throws UnsupportedOperationException {
return container.removeContainerProperty(propertyId);
}
/* Does the container contain the specified Item?
* Don't add a JavaDoc comment here, we use the default documentation
* from implemented interface.
*/
public boolean containsId(Object itemId) {
return container.containsId(itemId);
}
/* Gets the specified Item from the container.
* Don't add a JavaDoc comment here, we use the default documentation
* from implemented interface.
*/
public Item getItem(Object itemId) {
return container.getItem(itemId);
}
/* Gets the ID's of all Items stored in the Container
* Don't add a JavaDoc comment here, we use the default documentation
* from implemented interface.
*/
public Collection getItemIds() {
return container.getItemIds();
}
/* Gets the Property identified by the given itemId and propertyId from
* the Container
* Don't add a JavaDoc comment here, we use the default documentation
* from implemented interface.
*/
public Property getContainerProperty(Object itemId, Object propertyId) {
return container.getContainerProperty(itemId, propertyId);
}
/* Gets the ID's of all Properties stored in the Container
* Don't add a JavaDoc comment here, we use the default documentation
* from implemented interface.
*/
public Collection getContainerPropertyIds() {
return container.getContainerPropertyIds();
}
/* Gets the data type of all Properties identified by the given Property
* ID.
* Don't add a JavaDoc comment here, we use the default documentation
* from implemented interface.
*/
public Class getType(Object propertyId) {
return container.getType(propertyId);
}
/* Gets the number of Items in the Container.
* Don't add a JavaDoc comment here, we use the default documentation
* from implemented interface.
*/
public int size() {
return container.size();
}
/* Registers a new Item set change listener for this Container.
* Don't add a JavaDoc comment here, we use the default documentation
* from implemented interface.
*/
public void addListener(Container.ItemSetChangeListener listener) {
if (container instanceof Container.ItemSetChangeNotifier)
((Container.ItemSetChangeNotifier) container).addListener(listener);
}
/* Removes a Item set change listener from the object.
* Don't add a JavaDoc comment here, we use the default documentation
* from implemented interface.
*/
public void removeListener(Container.ItemSetChangeListener listener) {
if (container instanceof Container.ItemSetChangeNotifier)
((Container.ItemSetChangeNotifier) container).removeListener(
listener);
}
/* Registers a new Property set change listener for this Container.
* Don't add a JavaDoc comment here, we use the default documentation
* from implemented interface.
*/
public void addListener(Container.PropertySetChangeListener listener) {
if (container instanceof Container.PropertySetChangeNotifier)
((Container.PropertySetChangeNotifier) container).addListener(
listener);
}
/* Removes a Property set change listener from the object.
* Don't add a JavaDoc comment here, we use the default documentation
* from implemented interface.
*/
public void removeListener(Container.PropertySetChangeListener listener) {
if (container instanceof Container.PropertySetChangeNotifier)
((Container.PropertySetChangeNotifier) container).removeListener(
listener);
}
/**
* @see com.enably.tk.data.Container.Ordered#addItemAfter(Object, Object)
*/
public Item addItemAfter(Object previousItemId, Object newItemId)
throws UnsupportedOperationException {
// If the previous item is not in the container, fail
if (previousItemId != null && !containsId(previousItemId))
return null;
// Add the item to container
Item item = container.addItem(newItemId);
// Put the new item to its correct place
if (item != null)
addToOrderWrapper(newItemId, previousItemId);
return item;
}
/**
* @see com.enably.tk.data.Container.Ordered#addItemAfter(Object)
*/
public Object addItemAfter(Object previousItemId)
throws UnsupportedOperationException {
// If the previous item is not in the container, fail
if (previousItemId != null && !containsId(previousItemId))
return null;
// Add the item to container
Object id = container.addItem();
// Put the new item to its correct place
if (id != null)
addToOrderWrapper(id, previousItemId);
return id;
}
}