public class DiagramEditor extends GraphicalEditorWithFlyoutPalette implements IPersistableEditor{

    public void doSave(IProgressMonitor monitor) {
        // TODO Auto-generated method stub

        performSave(monitor, getEditorInput());
        getCommandStack().markSaveLocation();
    }

    @Override
    public void doSaveAs() {
        // TODO Auto-generated method stub
        
        Shell shell = getSite().getShell();
        final IEditorInput input = getEditorInput();

        
        SaveAsDialog dialog = new SaveAsDialog(shell);

        IFile original = (input instanceof IFileEditorInput) ? ((IFileEditorInput) input).getFile(): null;
                if (original != null){
            dialog.setOriginalFile(original);}
       
         dialog.create(); 
         int result = dialog.open(); 返回的是cancel或者ok
                 if (result == Window.CANCEL) {
                return;
            }
        
        IPath filePath = dialog.getResult();
        IFile file = null;
               if (filePath == null) {
            return;
        } else {
            file = ResourcesPlugin.getWorkspace().getRoot().getFile(filePath);
        }
               if (input.exists()) {

        } else {
            dialog.setErrorMessage(null);
            dialog.setMessage(WARN_FILEEXIST, IMessageProvider.WARNING);
            return;
        }
               if(file.exists()){
            
        }else{
            try {
                file.create(ResourceURLHelper.getNullInputStream(), true, null);
            } catch (CoreException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
               DiagramEditorInput newInput = new DiagramEditorInput(file.getLocation());
        
        performSave(getProgressMonitor(),newInput);
    }

    @Override
    public boolean isSaveAsAllowed() {
        // TODO Auto-generated method stub
        return true;
    }
    这个才是核心程序！重要！
    private void performSave(IProgressMonitor monitor, IEditorInput input) {
        if (diagram == null)
            return;

        diagram.doSaveXML();
        Document xmlTree = diagram.getDiagramDoc();

        if (xmlTree == null)
            return;

        IFile file = ResourceUtil.getFile(getEditorInput());

        OutputFormat format = OutputFormat.createPrettyPrint();
        try {
            FileWriter fileWriter;
            fileWriter = new FileWriter((String) input.getAdapter(Path.class));

            XMLWriter writer = new XMLWriter(fileWriter, format);
            writer.write(xmlTree);
            writer.close();

            if (file != null) {
                file.refreshLocal(IResource.DEPTH_ZERO,
                        new NullProgressMonitor());
            }

        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
@Override
    public void commandStackChanged(EventObject event) {
        // TODO Auto-generated method stub

        firePropertyChange(IEditorPart.PROP_DIRTY);
        super.commandStackChanged(event);
    }

    @Override
    public boolean isDirty() {
        // TODO Auto-generated method stub
        return getCommandStack().isDirty();
    }
}

public class DiagramModel extends AbstractModel {
   这些个都是diagram中包含的元素吗？
    private List<Object> children = new ArrayList<Object>();
    private List<Object> ports = new ArrayList<Object>();    
    private List<Object> texts = new ArrayList<Object>();
    private List<Object> containers = new ArrayList<Object>();
    private List<Object> portOps = new ArrayList<Object>();
    private List<Object> refers = new ArrayList<Object>();
    
    private ComponentInstanceModel component;    一直没搞懂这个componentInstanceModel和portInstanceModel是用来干嘛的。
    private DiagramHeadingModel diagramHead;     这个model也没搞懂是用来干嘛的。

    private String name;
    private Document diagramDoc;
    private Element rootElement,diagramElement,diagramExElement;
    
    public DiagramModel() {
        super();        
        name="";        
        initModel();
    }
public void initModel(){
        setName("Diagram");        
        setDiagramDoc(DocumentHelper.createDocument());        
        setRootElement(getDiagramDoc().addElement(ModelType.ELE_ROOT));
        setDiagramElement(getRootElement().addElement(ModelType.ELE_DIAGRAM));    
        setDiagramExElement(getRootElement().addElement(ModelType.ELE_DIAGRAMEX));？？？？
    }

    @Override
    public void doSaveXML() {
        // TODO Auto-generated method stub        
        this.addDiagramAttribute(ModelType.ATR_NAME, name);

        getDiagramHead().doSaveXML();
        getComponent().doSaveXML();        
        
        for(int i=0;i<getPorts().size();i++){
            ((ElementModel)getPorts().get(i)).doSaveXML();
        }
        
        for(int i=0;i<getTexts().size();i++){
            ((ElementModel)getTexts().get(i)).doSaveXML();
        }
    }
    
    
    protected void addDiagramAttribute(String name,String value){
        if(getDiagramElement()==null){
            return;
        }
        getDiagramElement().addAttribute(name, value);
    }
    
    protected void removeDiagramAttribute(String name){
        if(getDiagramElement()==null){
            return;
        }
        Attribute atr = getDiagramElement().attribute(name);
        if(atr != null){
            getDiagramElement().remove(atr);
        }
    }
    
    }

1. getDiagramHead().doSaveXML();

public class DiagramHeadingModel extends ElementModel {
        public DiagramHeadingModel() {
        super(ConstantResourceFactory.LABEL_DIAGRAMHEAD_MODEL,
                ConstantResourceFactory.ID_DIAGRAMHEAD_MODEL,
                ConstantResourceFactory.SIZE_DIAGRAMHEAD);
        // TODO Auto-generated constructor stub
        definition="";
        myCtype="";
        myReturn="";
        mySystem="";
        diagramType="";
        isRetShow=false;
        isSysShow=false;
        isRunsOnShow=false;
    }
        public void doSaveXML() {
        // TODO Auto-generated method stub
        super.doSaveXML();
        
        this.addXMLElementAttribute(ModelType.ATR_DIAGRAM,diagramType);
        this.addXMLElementAttribute(ModelType.ATR_DEFINITION,definition);
        if(isRunsOnShow()){
            this.addXMLElementAttribute(ModelType.ATR_RUNSON,myCtype);
        }
        else{
            this.removeXMLElementAttribute(ModelType.ATR_RUNSON);
        }
        
        if(isRetShow()){
            this.addXMLElementAttribute(ModelType.ATR_RETURN,myReturn);   ？？？？？
        }
        else{
            this.removeXMLElementAttribute(ModelType.ATR_RETURN);
        }
        
        if(isSysShow()){
            this.addXMLElementAttribute(ModelType.ATR_SYSTEM,mySystem);
        }
        else{
            this.removeXMLElementAttribute(ModelType.ATR_SYSTEM);
        }
    }
}

因为ComponentInstanceModel继承自portElementModel
所以先看portElementModel的dosaveXML（）

public abstract class PortElementModel extends ElementModel
{

    public PortElementModel(String label, String modelID, Dimension size) {
        super(label, modelID, size);
        // TODO Auto-generated constructor stub
        name="";
        type="";
    }

    public void doSaveXML() {
         // TODO Auto-generated method stub
        super.doSaveXML();
        this.addXMLElementAttribute(ModelType.ELE_NAME, name);
        this.addXMLElementAttribute(ModelType.ELE_TYPE, type);
    }  

}

getComponentInstance.doSaveXML();
{

public ComponentInstanceModel() {
        super(ConstantResourceFactory.LABEL_COMPONENTINSTANCE_MODEL,
                ConstantResourceFactory.ID_COMPONENTINSTANCE_MODEL,
                ConstantResourceFactory.SIZE_PORT_ELEMENT);
        // TODO Auto-generated constructor stub
        diagramType = "";
    }

public void doSaveXML() {
        // TODO Auto-generated method stub
        super.doSaveXML();        
        
        for(int i=0;i<children.size();i++){
            ((ElementModel)children.get(i)).doSaveXML();  子元素的dosavexml（）
        }
        
        if(tail!=null)
             tail.doSaveXML();这里的tail是elementmodel，所以调用的是elementmodel.dosavexml（）
    }

}