Add support for rowKey change
-----------------------------
Key: TRINIDAD-1613
URL: https://issues.apache.org/jira/browse/TRINIDAD-1613
Project: MyFaces Trinidad
Issue Type: Improvement
Components: Components
Affects Versions: 1.2.12-core
Environment: This is not specific to any environment setup.
Reporter: Jing Wu
RowKey is used in collection model to identify a row, it is safer to use than
row indicies because RowKeys are unaffected by mutations to the collection. But
there are cases where a RowKey instance can be changed. The proposal is to
define a clear way to raise and broadcast such event. The proposal contains the
following parts:
1. RowKeyChangeEvent - This newly introduced event is delivered when row key is
changed, the event should contain the value for both old row key and the new
row key.
2. RowKeyChangeListener - This is the listener that listens to
RowKeyChangeEvent, it has method onRowKeyChange() defined. Every time when
there is an RowKeyChangeEvent event, the implementor of RowKeyChangeListener
will get notified.
3. CollectionModel - The source that detects row key change and raises
RowKeyChangeEvent and invokes registered listeners.
Every module that holds reference to rowKey needs to implement
RowKeyChangeListener, register the listener with CollectionModel. When
collectionModel detects row key change and there are registered listeners, it
fires RowKeyChangeEvent to notify all the registered listeners, and the
affected module will react to the event, update the row key references.
/**
* Event that is generated when RowKey changes.
*/
public class RowKeyChangeEvent extends java.util.EventObject
{
/**
* Creates a new RowKeyChangeEvent
* @param source the source of the event
* @param oldRowKey the old row key.
* @param newRowKey the new row key.
*/
public RowKeyChangeEvent(
CollectionModel source,
Object oldRowKey,
Object newRowKey)
{
super(source);
_oldRowKey = oldRowKey;
_newRowKey = newRowKey;
}
/**
* retrieve the old key from the event
* @return the old key of the event.
*/
public Object getOldRowKey()
{
return _oldRowKey;
}
/**
* retrieve the new key from the event
* @return the new key of the event.
*/
public Object getNewRowKey()
{
return _newRowKey;
}
private final Object _oldRowKey;
private final Object _newRowKey;
}
/**
* Listener for RowKeyChangeEvent.
*/
public interface RowKeyChangeListener
{
public void onRowKeyChange(RowKeyChangeEvent event);
}
public abstract class CollectionModel extends DataModel
implements RowKeyIndex
{
...
/**
* register the specified listener with the collection model.
* @param listener The listener to register with the collection model
*/
public void addRowKeyChangeListener(RowKeyChangeListener listener)
{
_rowKeyChangeListeners.add(listener);
}
/**
* unregister the specified listener with the collection model.
* @param listener The listener to unregister with the collection model
*/
public void removeRowKeyChangeListener(RowKeyChangeListener listener)
{
_rowKeyChangeListeners.remove(listener);
}
/**
* retrieve the registered listeners
* @return the registered listeners
*/
public void Set<RowKeyChangeListener> getRowKeyChangeListeners()
{
return Collections.unmodifiableSet(_rowKeyChangeListeners);
}
...
private Set<RowKeyChangeListener> _rowKeyChangeListeners = new
HashSet<RowKeyChangeListener>();
}
Notes regarding the proposal:
(1) For better performance, if a module holds references to row key, but knows
that the row key will not change, e.g. read only table, the module should not
register itself as listener to collection model.
(2) If a module has difference lifecycle than the collection model, the module
needs to re-register with collection model as necessarily.
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