public abstract class Change extends Object implements IAdaptable
Change object is typically created by
calling Refactoring.createChange(). This class should be
subclassed by clients wishing to provide new changes.
Changes are best executed by using a PerformChangeOperation. If clients
execute a change directly then the following life cycle has to be honored:
initializeValidationState has to be called.isValid can be used to determine if a change
can still be applied to the workspace. If the method returns a RefactoringStatus with a severity of FATAL then the change has to be
treated as invalid. Performing an invalid change isn't allowed and
results in an unspecified result. This method can be called multiple
times.
dispose must be called.initializeValidationState. There is no guarantee
that initializeValidationState, isValid
or perform has been called, before dispose
is called.
Change change= createChange();
try {
change.initializeValidationState(pm);
....
if (!change.isEnabled())
return;
RefactoringStatus valid= change.isValid(new SubProgressMonitor(pm, 1));
if (valid.hasFatalError())
return;
Change undo= change.perform(new SubProgressMonitor(pm, 1));
if (undo != null) {
undo.initializeValidationState(new SubProgressMonitor(pm, 1));
// do something with the undo object
}
} finally {
change.dispose();
}
It is important that implementors of this abstract class provide an adequate
implementation of isValid and that they provide an undo change
via the return value of the method perform. If no undo can be
provided then the perform method is allowed to return null. But
implementors should be aware that not providing an undo object for a change
object that is part of a larger change tree will result in the fact that for
the whole change tree no undo object will be present.
Changes which are returned as top-level changes (e.g. by Refactoring.createChange())
can optionally return a descriptor object of the refactoring which created this change object.
Clients may subclass this class.
| Modifier | Constructor and Description |
|---|---|
protected |
Change()
Constructs a new change object.
|
| Modifier and Type | Method and Description |
|---|---|
void |
dispose()
Disposes this change.
|
Object |
getAdapter(Class adapter)
Returns an object which is an instance of the given class
associated with this object.
|
Object[] |
getAffectedObjects()
Returns the elements affected by this change or
null if
the affected elements cannot be determined. |
ChangeDescriptor |
getDescriptor()
Returns a descriptor of this change.
|
abstract Object |
getModifiedElement()
Returns the element modified by this
Change. |
abstract String |
getName()
Returns the human readable name of this change.
|
Change |
getParent()
Returns the parent change.
|
abstract void |
initializeValidationData(IProgressMonitor pm)
Hook method to initialize some internal state to provide an adequate answer
for the
isValid method. |
boolean |
isEnabled()
Returns whether this change is enabled or not.
|
abstract RefactoringStatus |
isValid(IProgressMonitor pm)
Verifies that this change object is still valid and can be executed by calling
perform. |
abstract Change |
perform(IProgressMonitor pm)
Performs this change.
|
void |
setEnabled(boolean enabled)
Sets whether this change is enabled or not.
|
void |
setEnabledShallow(boolean enabled)
Sets the enablement state of this change in a shallow way.
|
public ChangeDescriptor getDescriptor()
Subclasses of changes created by
Refactoring.createChange(IProgressMonitor) should override this
method to return a RefactoringChangeDescriptor. A change tree
created by a particular refactoring is supposed to contain at most one
change which returns a refactoring descriptor. Refactorings usually
return an instance of CompositeChange in their
Refactoring.createChange(IProgressMonitor) method which
implements this method. The refactoring framework searches the change
tree top-down until a refactoring descriptor is found.
null if this
change does not provide a change descriptor.public abstract String getName()
null.public boolean isEnabled()
true if the change is enabled; false
otherwise.public void setEnabled(boolean enabled)
enabled - true to enable this change;
false otherwisepublic final void setEnabledShallow(boolean enabled)
enabled - true to enable this change;
false otherwisepublic Change getParent()
null if no
parent exists.public abstract void initializeValidationData(IProgressMonitor pm)
isValid method. This method gets called after a change
or a whole change tree has been created.
Typically this method is implemented in one of the following ways:
dispose.isValid is called.
For example, a change object that manipulates the content of an IFile
could either listen to resource changes and detect that the file got changed or
it could remember some content stamp and compare it with the actual content stamp
when isValid is called.
pm - a progress monitorpublic abstract RefactoringStatus isValid(IProgressMonitor pm) throws CoreException, OperationCanceledException
perform. If a refactoring status with a severity of RefactoringStatus.FATAL is returned then the change has to be treated as invalid
and can no longer be executed. Performing such a change produces an unspecified
result and will very likely throw an exception.
This method is also called by the UndoManager to decide if
an undo or redo change is still valid and therefore can be executed.
pm - a progress monitor.CoreException - if an error occurred during validation check. The change
is to be treated as invalid if an exception occursOperationCanceledException - if the validation check got canceledpublic abstract Change perform(IProgressMonitor pm) throws CoreException
IProgressMonitor.isCanceled() since canceling a change tree in the
middle of its execution leaves the workspace in a half changed state.pm - a progress monitornull if no
undo is providedCoreException - if an error occurred during change executionpublic void dispose()
initializeValidationState.
Subclasses may override this method.
public abstract Object getModifiedElement()
Change. The method may return
null if the change isn't related to an element.public Object[] getAffectedObjects()
null if
the affected elements cannot be determined. Returns an empty array
if the change doesn't modify any elements.
This default implementation returns null to indicate that
the affected elements are unknown. Subclasses should reimplement this method
if they can compute the set of affected elements.
null if
the affected elements cannot be determinedpublic Object getAdapter(Class adapter)
null if
no such object can be found.getAdapter in interface IAdaptableadapter - the adapter class to look upnull if this object does not
have an adapter for the given classGuidelines for using Eclipse APIs. Copyright (c) IBM Corp. and others 2000, 2006. All rights reserved.