private Element generateGraphicsNode(Document doc, ClassGraphics gr) {

    Element graphicsEl = doc.createElement(EL_GRAPHICS);

    Element bounds = doc.createElement(EL_BOUNDS);
    graphicsEl.appendChild(bounds);
    bounds.setAttribute(ATR_X, Integer.toString(gr.getBoundX()));
    bounds.setAttribute(ATR_Y, Integer.toString(gr.getBoundY()));
    bounds.setAttribute(ATR_WIDTH, Integer.toString(gr.getBoundWidth()));
    bounds.setAttribute(ATR_HEIGHT, Integer.toString(gr.getBoundHeight()));

    for (Shape shape : gr.getShapes()) {

      if (shape instanceof Rect) {
        Rect rect = (Rect) shape;
        Element rectEl = doc.createElement(EL_RECT);
        graphicsEl.appendChild(rectEl);
        rectEl.setAttribute(ATR_X, Integer.toString(rect.getX()));
        rectEl.setAttribute(ATR_Y, Integer.toString(rect.getY()));
        rectEl.setAttribute(ATR_WIDTH, Integer.toString(rect.getWidth()));
        rectEl.setAttribute(ATR_HEIGHT, Integer.toString(rect.getHeight()));
        rectEl.setAttribute(ATR_COLOUR, Integer.toString(rect.getColor().getRGB()));
        rectEl.setAttribute(ATR_FILLED, Boolean.toString(rect.isFilled()));
        rectEl.setAttribute(ATR_FIXED, Boolean.toString(rect.isFixed()));
        rectEl.setAttribute(ATR_STROKE, Float.toString(rect.getStroke().getLineWidth()));
        rectEl.setAttribute(ATR_LINETYPE, Float.toString(rect.getLineType()));
        rectEl.setAttribute(ATR_TRANSPARENCY, Integer.toString(rect.getTransparency()));
      } else if (shape instanceof Text) {
        Text text = (Text) shape;
        Element textEl = doc.createElement(EL_TEXT);
        textEl.setAttribute(ATR_STRING, text.getText());
        textEl.setAttribute(ATR_X, Integer.toString(text.getX()));
        textEl.setAttribute(ATR_Y, Integer.toString(text.getY()));
        textEl.setAttribute(ATR_FONTNAME, text.getFont().getName());
        textEl.setAttribute(ATR_FONTSIZE, Integer.toString(text.getFont().getSize()));
        textEl.setAttribute(ATR_FONTSTYLE, Integer.toString(text.getFont().getStyle()));
        textEl.setAttribute(ATR_TRANSPARENCY, Integer.toString(text.getTransparency()));
        textEl.setAttribute(ATR_COLOUR, Integer.toString(text.getColor().getRGB()));
        graphicsEl.appendChild(textEl);
      } // TODO handle the rest of shapes
    }

    return graphicsEl;
  }
  private Node generateFieldNode(Document doc, ClassField field) {
    Element fieldEl = doc.createElement(EL_FIELD);

    fieldEl.setAttribute(ATR_NAME, field.getName());
    fieldEl.setAttribute(ATR_TYPE, field.getType());

    if (field.isInput()) fieldEl.setAttribute(ATR_NATURE, "input");
    else if (field.isGoal()) fieldEl.setAttribute(ATR_NATURE, "goal");

    if (field.getValue() != null) fieldEl.setAttribute(ATR_VALUE, field.getValue());

    return fieldEl;
  }
  private Element generatePortNode(Document doc, Port port) {
    Element portEl = doc.createElement(EL_PORT);

    portEl.setAttribute(ATR_NAME, port.getName());
    portEl.setAttribute(ATR_TYPE, port.getType());
    portEl.setAttribute(ATR_X, Integer.toString(port.getX()));
    portEl.setAttribute(ATR_Y, Integer.toString(port.getY()));
    portEl.setAttribute(ATR_PORT_CONNECTION, port.isArea() ? "area" : "");
    portEl.setAttribute(ATR_STRICT, Boolean.toString(port.isStrict()));
    portEl.setAttribute(ATR_MULTI, Boolean.toString(port.isMulti()));

    return portEl;
  }
  public void addPackageClass(PackageClass pClass) {

    Document doc;
    try {
      doc = getDocument();
    } catch (Exception e) {
      e.printStackTrace();
      return;
    }

    String name = pClass.getName();

    // check if such class exists and remove duplicates
    Element rootEl = doc.getDocumentElement();
    NodeList classEls = rootEl.getElementsByTagName(EL_CLASS);
    for (int i = 0; i < classEls.getLength(); i++) {
      Element nameEl = getElementByName((Element) classEls.item(i), EL_NAME);
      if (name.equals(nameEl.getTextContent())) {
        rootEl.removeChild(classEls.item(i));
      }
    }

    Element classNode = doc.createElement(EL_CLASS);
    doc.getDocumentElement().appendChild(classNode);
    classNode.setAttribute(ATR_TYPE, PackageClass.ComponentType.SCHEME.getXmlName());
    classNode.setAttribute(ATR_STATIC, "false");

    Element className = doc.createElement(EL_NAME);
    className.setTextContent(name);
    classNode.appendChild(className);

    Element desrc = doc.createElement(EL_DESCRIPTION);
    desrc.setTextContent(pClass.getDescription());
    classNode.appendChild(desrc);

    Element icon = doc.createElement(EL_ICON);
    icon.setTextContent(pClass.getIcon());
    classNode.appendChild(icon);

    // graphics
    classNode.appendChild(generateGraphicsNode(doc, pClass.getGraphics()));

    // ports
    List<Port> ports = pClass.getPorts();
    if (!ports.isEmpty()) {
      Element portsEl = doc.createElement(EL_PORTS);
      classNode.appendChild(portsEl);

      for (Port port : ports) {
        portsEl.appendChild(generatePortNode(doc, port));
      }
    }

    // fields
    Collection<ClassField> fields = pClass.getFields();
    if (!fields.isEmpty()) {
      Element fieldsEl = doc.createElement(EL_FIELDS);
      classNode.appendChild(fieldsEl);

      for (ClassField cf : fields) {
        fieldsEl.appendChild(generateFieldNode(doc, cf));
      }
    }

    // write
    try {
      writeDocument(doc, new FileOutputStream(xmlFile));
    } catch (FileNotFoundException e) {
      e.printStackTrace();
    }
  }