• User selects an object (or set of objects) and chooses to invoke a particular refactoring on it.
• Refactoring pre-conditions are checked - whether a given refactoring can be invoked on a given object (or set of objects) or not. User needs to be presented with errors (if any). The errors can be fatal or non-fatal. If an error is fatal, it means the refactoring cannot be performed, if it is not fatal, user should be notified of the problem but still be able to proceed with the refactoring.
• User sets parameters of the refactoring - each refactoring has some input parameters (e.g. new name for an element in case of Rename refactoring). These parameters need to be set by the client.
• Entered values of refactoring parameters are checked - errors (if any) are presented to the user.
• Refactoring collects all changes that need to be performed and presents them to the user.
• User can choose to not perform a particular set of proposed changes.
• Refactoring is performed - all the changes confirmed by user are made to the source code.

1. A module wants to implement refactoring features for their own elements. For instance Java Refactoring module wants to implement Refactoring for Java elements.
2. A module wants to participate in existing refactoring. E.g. refactoring of java files requires refactoring of non-java files in J2EE area. When a code is refactored, these non-java files need to be refactored too. We can mention JSP files or deployment descriptors as an example.
3. A module introduces some hidden relationships between several elements. E.g. a single logical EJB consists of several physical classes. When one of these classes are refactored, the other classes need to be refactored as well.
4. A module generates some derived code into the guarded blocks. In such case it is desirable that the provider of the guarded block refactors the guarded code, since the refactoring module itself has no knowledge of where the guarded code comes from.

Refactoring API Example:

        FileObject fo = ...com/company/Test.java...
        RefactoringSession renameSession = RefactoringSession.create("Rename Class");
        refactoring = new RenameRefactoring(fo);
        Problem pre = refactoring.preCheck();
        if (pre!=null && pre.isFatal()) {
          //fatal problem in precheck
          return;
        }
        refactoring.setNewName("RenamedTest");
        Problem p = refactoring.prepare(renameSession);
        
        if (p!=null && p.isFatal()) {
          //fatal problem in precheck
          return;
        }
        
        renameSession.doRefactoring(true /* saveAll */);

Refactoring SPI permit other modules to plug into existing refactorings and allow them to participate. Client of SPI must implement factory class RefactoringPluginFactory and register this class into Lookup.

Intention: Create a plugin for RenameRefactoring, which will participate in existing refactoring (let say in java refactoring) and renames references in XML files.

//implementation of factory class
public class J2EERefactoringFactory implements RefactoringPluginFactory {
    
    public RefactoringPlugin createInstance(AbstractRefactoring refactoring) {
    
        if (refactoring instanceof RenameRefactoring) {
            //return our custom instance for RenameRefactoring
            if (wantToParticipate(refactoring.getRefactoredObject())
                return new J2EERenameRefactoringPlugin((RenameRefactoring) refactoring);
        }
        
        if (refactoring instanceof ... {
            ...
        }

        return null;
    }
    
}

META-INF/services/org.netbeans.modules.refactoring.spi.RefactoringPluginFactory

and implement RefactoringPlugin interface:

//implementation of RefactoringPlugin
public class J2EERenameRefactoringPlugin implements RefactoringPlugin {
    
    private RenameRefactoring refactoring;
    
    public J2EERenameRefactoringPlugin(RenameRefactoring refactoring) { 
        this.refactoring = refactoring;
    }
 
    public Problem preCheck() {
        ...
    }
    
    public Problem checkParameters() {
        ...
    }
    
    public Problem fastCheckParameters() {
        ...
    }
    
    public void cancelRequest() {
        ...
    }
    
    public Problem prepare(RefactoringElementsBag refactoringElements) {
        RenameRefactoring renameRefactor = ((RenameRefactoring)refactoring);
        Object element = renameRefactor.getRefactoredObject();
        if (...) {
           ...
           //lets add our RefactoringElements for usages found in XML files 
           refactoringElements.add(refactoring, new XMLRenameRefactoringElement());
        }
        return null;
    }

    public class XMLRenameRefactoringElement implements RefactoringElementImplementation {

        public void performChange() {
            //do change
        }
    }

public class MyProvider extends ActionsImplementationProvider {
    
  public boolean canRename(Lookup lookup) {
    Node[] nodes = lookup.lookupAll(Node.class);
    if (..one node selected and the node belongs to html...)
      return true;
    else 
      return fals;
 }

  public Runnable renameImpl(Lookup selectedNodes) {
    Node[] nodes = lookup.lookupAll(Node.class);
    final FileObject fo = getFileFromNode(nodes[0]);
    return new Runnable() {
      public void run() {
        UI.openRefactoringUI(new RenameRefactoringUI(fo);
      }
    }    
  }
}

public TreeElement getTreeElement(Object o) {
.
.
if (o instanceof SourceGroup) {
  return new SourceGroupTreeElement((SourceGroup)o);
} else if (o instanceof SomethingFromJava) {
   return new SomethingFromJavaTreeElement((SomethingFromJava) o);
}

• Module wants to add common Refactoring Action into popup.
  See RefactoringActionsFactory
• http://wiki.netbeans.org/wiki/view/RefactoringFAQ