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org.eclipse.ltk.core.refactoring
Class Change  

java.lang.Object
  org.eclipse.ltk.core.refactoring.Change

All Implemented Interfaces:

org.eclipse.core.runtime.IAdaptable

Direct Known Subclasses:

CompositeChange, NullChange, TextChange, UndoTextFileChange

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public abstract class Change

extends java.lang.Object

implements org.eclipse.core.runtime.IAdaptable

An abstract base implementation for object representing a generic change to the workbench. A 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:

• 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. An disabled change must not be executed. The perform method can only be called once. After a change as 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 register during the method initializeValidationState. There is no guarantee that initializeValidationState, isValid or perform has been called, before dispose is called.

Below 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.

Clients may subclass this class.

Since:

3.0

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Field Summary
private  boolean	fIsEnabled
private  Change	fParent

 

Constructor Summary
protected	Change()           Constructs a new change object.

 

Method Summary
void	dispose()           Disposes this change.
java.lang.Object	getAdapter(java.lang.Class adapter)           null
abstract  java.lang.Object	getModifiedElement()           Returns the element modified by this Change.
abstract  java.lang.String	getName()           Returns the human readable name of this change.
Change	getParent()           Returns the parent change.
abstract  void	initializeValidationData(org.eclipse.core.runtime.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(org.eclipse.core.runtime.IProgressMonitor pm)           Verifies that this change object is still valid and can be executed by calling perform.
abstract  Change	perform(org.eclipse.core.runtime.IProgressMonitor pm)           Performs this change.
void	setEnabled(boolean enabled)           Sets whether this change is enabled or not.
(package private)  void	setParent(Change parent)           Sets the parent of this change.

 

Methods inherited from class java.lang.Object

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

 

Field Detail

fParent

private Change fParent

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fIsEnabled

private boolean fIsEnabled

Constructor Detail

Change

protected Change()

Constructs a new change object.

Method Detail

getName

public abstract java.lang.String getName()

Returns the human readable name of this change. The name MUST not be null.

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isEnabled

public boolean isEnabled()

Returns whether this change is enabled or not. Disabled changes must not be executed.

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setEnabled

public void setEnabled(boolean enabled)

Sets whether this change is enabled or not.

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getParent

public Change getParent()

Returns the parent change. Returns null if no parent exists.

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setParent

void setParent(Change parent)

Sets the parent of this change. Requires that this change isn't already connected to a parent. The parent can be null to disconnect this change from a parent.

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initializeValidationData

public abstract void initializeValidationData(org.eclipse.core.runtime.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.

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isValid

public abstract RefactoringStatus isValid(org.eclipse.core.runtime.IProgressMonitor pm)
                                   throws org.eclipse.core.runtime.CoreException,
                                          org.eclipse.core.runtime.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 55 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.

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perform

public abstract Change perform(org.eclipse.core.runtime.IProgressMonitor pm)
                        throws org.eclipse.core.runtime.CoreException

Performs this change. If this method is call on an invalid or disabled change object the result is unspecified. Changes should in general not respond to IProgressMonitor.isCanceled()>IProgressMonitor.isCanceled() 55 since canceling a change tree in the middle of its execution leaves the workspace in a half changed state.

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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.

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getModifiedElement

public abstract java.lang.Object getModifiedElement()

Returns the element modified by this Change. The method may return null if the change isn't related to an element.

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getAdapter

public java.lang.Object getAdapter(java.lang.Class adapter)

null

Specified by:

getAdapter in interface org.eclipse.core.runtime.IAdaptable

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Home >> All >> org >> eclipse >> ltk >> core >> [ refactoring overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

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