org.eclipse.ltk.core.refactoring
Class Change
java.lang.Object
org.eclipse.ltk.core.refactoring.Change
-
All Implemented Interfaces:
-
IAdaptable
-
Direct Known Subclasses:
-
CompositeChange,
NullChange,
ResourceChange,
TextEditBasedChange,
UndoTextFileChange
-
public abstract class Change
- extends
Object
- implements
IAdaptable
An abstract base implementation for object representing a generic change
to the workbench. A Change object is typically created by
calling
Refactoring.createChange(IProgressMonitor). 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:
- After a single change or a tree of changes has been created, the
method
initializeValidationState has to be called.
- The method
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.
- Then the method
perform can be called. A disabled change
must not be executed. The perform method can only be called
once. After a change has been executed, only the method dispose
must be called.
- the method
dispose has to be called either after the
perform method
has been called or if a change is no longer needed. The second case
for example occurs when the undo stack gets flushed and all change
objects managed by the undo stack are no longer needed. The method
dispose is typically implemented to unregister listeners
registered during the
method initializeValidationState. There is no guarantee
that initializeValidationState, isValid,
or perform has been called before dispose
is called.
Here is a code snippet that can be used to execute a change:
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.
-
Since:
- 3.0
|
Constructor Summary
|
protected
|
Change
()
Constructs a new change object. |
|
Methods inherited from class java.lang.
Object
|
clone,
equals,
finalize,
getClass,
hashCode,
notify,
notifyAll,
toString,
wait,
wait,
wait
|
Change
protected Change()
- Constructs a new change object.
getDescriptor
public
ChangeDescriptor getDescriptor()
- Returns a descriptor of this change.
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.
-
-
-
Returns:
- a descriptor of this change, or
null if this
change does not provide a change descriptor. -
Since:
- 3.2
getName
public abstract
String getName()
- Returns the human readable name of this change. The
name MUST not be
null.
-
-
-
Returns:
- the human readable name of this change
isEnabled
public boolean isEnabled()
- Returns whether this change is enabled or not. Disabled changes
must not be executed.
-
-
-
Returns:
-
true if the change is enabled; false
otherwise.
setEnabled
public void setEnabled(boolean enabled)
- Sets whether this change is enabled or not.
-
-
-
Parameters:
-
enabled - true to enable this change;
false otherwise
setEnabledShallow
public final void setEnabledShallow(boolean enabled)
- Sets the enablement state of this change in a shallow way.
For changes having children this means that only this change's
enablement state changes. The children are left untouched.
-
-
-
Parameters:
-
enabled - true to enable this change;
false otherwise -
Since:
- 3.1
getParent
public
Change getParent()
- Returns the parent change. Returns
null if no
parent exists.
-
-
-
Returns:
- the parent change
initializeValidationData
public abstract void initializeValidationData(
IProgressMonitor pm)
- Hook method to initialize some internal state to provide an adequate answer
for the
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:
- the change hooks up a listener on some delta notification mechanism
and marks itself as invalid if it receives a certain delta. Is this
the case the implementor must take care of unhooking the listener
in
dispose.
- the change remembers some information allowing to decide if a change
object is still valid when
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.
-
-
-
Parameters:
-
pm - a progress monitor
isValid
public abstract
RefactoringStatus isValid(
IProgressMonitor pm)
throws
CoreException,
OperationCanceledException
- Verifies that this change object is still valid and can be executed by calling
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.
-
-
-
Parameters:
-
pm - a progress monitor.
-
Returns:
- a refactoring status describing the outcome of the validation check
-
Throws:
-
CoreException
- if an error occurred during validation check. The change
is to be treated as invalid if an exception occurs
-
OperationCanceledException
- if the validation check got canceled
perform
public abstract
Change perform(
IProgressMonitor pm)
throws
CoreException
- Performs this change. If this method is called on an invalid or disabled change
object the result is unspecified. Changes should in general not respond to
IProgressMonitor.isCanceled() since canceling a change tree in the
middle of its execution leaves the workspace in a half changed state.
-
-
-
Parameters:
-
pm - a progress monitor
-
Returns:
- the undo change for this change object or
null if no
undo is provided
-
Throws:
-
CoreException
- if an error occurred during change execution
dispose
public void dispose()
- Disposes this change. Subclasses that override this method typically
unregister listeners which got registered during the call to
initializeValidationState.
Subclasses may override this method.
-
-
getModifiedElement
public abstract
Object getModifiedElement()
- Returns the element modified by this
Change. The method may return
null if the change isn't related to an element.
-
-
-
Returns:
- the element modified by this change
getAffectedObjects
public
Object[] getAffectedObjects()
- Returns the elements affected by this change or
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.
-
-
-
Returns:
- the elements affected by this change or
null if
the affected elements cannot be determined -
Since:
- 3.1
getAdapter
public
Object getAdapter(
Class adapter)
- Returns an object which is an instance of the given class
associated with this object. Returns
null if
no such object can be found.
-
-
Specified by:
-
getAdapter
in interface
IAdaptable
-
-
Parameters:
-
adapter - the adapter class to look up
-
Returns:
- a object castable to the given class,
or
null if this object does not
have an adapter for the given class
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