org.das2.system

Class ChangesSupport

java.lang.Object

org.das2.system.ChangesSupport

public class ChangesSupport
extends java.lang.Object

Support class for encapsulating implementation of pendingChanges and mutator locks. PendingChanges are a way of notifying the bean and other clients using the bean that changes are coming to the bean. mutatorLock() is a way for a client to get exclusive, read-only access to a bean. This also sets the valueAdjusting property. See http://das2.org/wiki/index.php/Pending_changes (Wiki was lost, but may be recoverable.)

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	PROP_PENDINGCHANGES
static java.lang.String	PROP_VALUEADJUSTING

Constructor Summary

Constructors

Constructor and Description
ChangesSupport(java.beans.PropertyChangeSupport pcs, java.lang.Object parent) if the propertyChangeSupport is provided, then change messages will be sent to it directly.

Method Summary

Modifier and Type	Method and Description
void	addPropertyChangeListener(java.beans.PropertyChangeListener listener)
void	changePerformed(java.lang.Object client, java.lang.Object lockObject) the change is complete, and as far as the client is concerned, the canvas is valid.
java.util.Map	getChangesPending() return a map listing the pending changes.
boolean	isPendingChanges() true if someone has registered a pending change.
boolean	isPendingChanges(java.lang.Object lockObject) allow check for particular change.
boolean	isValueAdjusting() true when the bean state is rapidly changing.
java.util.concurrent.locks.Lock	mutatorLock() one client will have write access to the bean, and when unlock is called, a "valueAdjusting" property change event is fired.
void	pendingChanges(java.util.Map<java.lang.Object,java.lang.Object> changes) return a list of all the pending changes.
void	performingChange(java.lang.Object client, java.lang.Object lockObject) performingChange tells that the change is about to be performed.
void	registerPendingChange(java.lang.Object client, java.lang.Object lockObject) the client knows a change will be coming, and the canvas' clients should know that its current state will change soon.
void	removePropertyChangeListener(java.beans.PropertyChangeListener listener)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

PROP_PENDINGCHANGES

public static final java.lang.String PROP_PENDINGCHANGES

See Also:

Constant Field Values

PROP_VALUEADJUSTING

public static final java.lang.String PROP_VALUEADJUSTING

See Also:

Constant Field Values

Constructor Detail

ChangesSupport

public ChangesSupport(java.beans.PropertyChangeSupport pcs,
                      java.lang.Object parent)

if the propertyChangeSupport is provided, then change messages will be sent to it directly. If null, then one is created with the parent as the source.

Parameters:

pcs - the PropertyChangeSupport

parent - the object this is supporting, for debugging purposes.

Method Detail

registerPendingChange

public void registerPendingChange(java.lang.Object client,
                                  java.lang.Object lockObject)

the client knows a change will be coming, and the canvas' clients should know that its current state will change soon. Example pending changes would be:

• layout because tick labels are changing
• data is loading

Note, it is okay to call this multiple times for the same client and lock object.

Parameters:

client - the object that will perform the change. This allows the canvas (and developers) identify who has registered the change.

lockObject - object identifying the change.

pendingChanges

public void pendingChanges(java.util.Map<java.lang.Object,java.lang.Object> changes)

return a list of all the pending changes. These are returned in a Map that goes from pending change to change manager.

Parameters:

changes - a Map to which the changes will be added.

See Also:

getChangesPending()

performingChange

public void performingChange(java.lang.Object client,
                             java.lang.Object lockObject)

performingChange tells that the change is about to be performed. This is a place holder in case we use a mutator lock, but currently does nothing. If the change has not been registered, it will be registered implicitly. This will increment the internal count of how many times the change ought to occur.

Parameters:

client - the object that is mutating the bean.

lockObject - an object identifying the change.

changePerformed

public void changePerformed(java.lang.Object client,
                            java.lang.Object lockObject)

the change is complete, and as far as the client is concerned, the canvas is valid.

Parameters:

client - the object that is mutating the bean.

lockObject - an object identifying the change.

isPendingChanges

public boolean isPendingChanges()

true if someone has registered a pending change.

Returns:

true if someone has registered a pending change.

isPendingChanges

public boolean isPendingChanges(java.lang.Object lockObject)

allow check for particular change.

Parameters:

lockObject - object identifying the change.

Returns:

true if that particular change is pending.

getChangesPending

public java.util.Map getChangesPending()

return a map listing the pending changes. This is a thread-safe read-only copy.

Returns:

a map listing the pending changes.

See Also:

pendingChanges(java.util.Map<java.lang.Object, java.lang.Object>)

isValueAdjusting

public boolean isValueAdjusting()

true when the bean state is rapidly changing.

Returns:

true when the bean state is rapidly changing.

mutatorLock

public java.util.concurrent.locks.Lock mutatorLock()

one client will have write access to the bean, and when unlock is called, a "valueAdjusting" property change event is fired. In the future, this will return null if the lock is already out, but for now, clients should check the valueIsAdjusting property.

Returns:

the lock or null.

addPropertyChangeListener

public void addPropertyChangeListener(java.beans.PropertyChangeListener listener)

removePropertyChangeListener

public void removePropertyChangeListener(java.beans.PropertyChangeListener listener)