javaxmlsaveloadjgraphx

Save and load graph in xml file using JGraphx

In JGraphx, it is possible to draw custom vertex. I defined the custom object and used that as the value of the vertex. To save and load the graph as xml file, the custom object has been registered as follows:

mxCodecRegistry.addPackage(the path of the custom object); 
mxCodecRegistry.register(new mxObjectCodec(new Myobject()));

enter image description here When saving the vertex, the custom object is saved as the value of the vertex. When I load the xml file, the value of the vertex is returned null though the vertex is shown correctly. In other words, the graphical display is fine but when I want to read the properties of the object or even move it around, the following error appears:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at com.mxgraph.swing.handler.mxVertexHandler.createHandles(Unknown Source)
    at com.mxgraph.swing.handler.mxCellHandler.refresh(Unknown Source)
    at com.mxgraph.swing.handler.mxCellHandler.<init>(Unknown Source)
    at com.mxgraph.swing.handler.mxVertexHandler.<init>(Unknown Source)
    at com.mxgraph.swing.mxGraphComponent.createHandler(Unknown Source)
    at com.mxgraph.swing.handler.mxSelectionCellsHandler.refresh(Unknown Source)
    at com.mxgraph.swing.handler.mxSelectionCellsHandler$1.invoke(Unknown Source)
    at com.mxgraph.util.mxEventSource.fireEvent(Unknown Source)
    at com.mxgraph.util.mxEventSource.fireEvent(Unknown Source)
    at com.mxgraph.view.mxGraphSelectionModel$mxSelectionChange.execute(Unknown Source)
    at com.mxgraph.view.mxGraphSelectionModel.changeSelection(Unknown Source)
    at com.mxgraph.view.mxGraphSelectionModel.setCells(Unknown Source)
    at com.mxgraph.view.mxGraphSelectionModel.setCell(Unknown Source)
    at com.mxgraph.view.mxGraph.setSelectionCell(Unknown Source)
    at com.mxgraph.swing.mxGraphComponent.selectCellForEvent(Unknown Source)
    at com.mxgraph.swing.handler.mxGraphHandler.mousePressed(Unknown Source)
    at java.awt.AWTEventMulticaster.mousePressed(Unknown Source)
    at java.awt.AWTEventMulticaster.mousePressed(Unknown Source)
    at java.awt.AWTEventMulticaster.mousePressed(Unknown Source)
    at java.awt.Component.processMouseEvent(Unknown Source)
    at javax.swing.JComponent.processMouseEvent(Unknown Source)
    at java.awt.Component.processEvent(Unknown Source)
    at java.awt.Container.processEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Window.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$500(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

Which shows that the object is null. I followed the documentation and registered my object. Here is the GUI:

package graphicalUserInterface;

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.LayoutManager;
import java.awt.Point;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

import javax.swing.BoxLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;

import com.mxgraph.canvas.mxGraphics2DCanvas;
import com.mxgraph.io.mxCodecRegistry;
import com.mxgraph.io.mxObjectCodec;
import com.mxgraph.model.mxCell;
import com.mxgraph.shape.mxStencilShape;
import com.mxgraph.swing.mxGraphComponent;
import com.mxgraph.util.mxConstants;
import com.mxgraph.util.mxEvent;
import com.mxgraph.util.mxEventObject;
import com.mxgraph.util.mxUtils;
import com.mxgraph.util.mxEventSource.mxIEventListener;
import com.mxgraph.view.mxGraph;
import com.mxgraph.view.mxStylesheet;

import netElements.Valve;

public class GUIBoard extends JPanel {

    private mxGraph _graph;
    private mxGraphComponent _graphComponent;
    private JPanel _panel;
    private JFrame _frame;
    private ArrayList<Valve> _valves;

    public GUIBoard(JFrame frame) {
        // TODO Auto-generated constructor stub
        _frame=frame;
        initialize();
    }

    private void initialize(){
        _panel=new JPanel();
        _panel.setLayout(new BoxLayout(_panel, BoxLayout.Y_AXIS));

        addToRegistry("Images/valve.shape");
        /**
         * Define a new object to be saved in the Model
         */
        mxCodecRegistry.addPackage(Valve.class.getPackage().toString());
        mxCodecRegistry.register(new mxObjectCodec(new Valve()));


        _graph=new mxGraph() {

            public boolean isCellFoldable(Object cell, boolean collapse)
            {
                return false;
            }

            public String convertValueToString(Object cell)
            {
                Object value = null ;
                if (cell instanceof mxCell)
                {
                    value = ((mxCell) cell).getValue();

                    if (value instanceof Valve)
                    {
                        Valve v=(Valve) value;

                        return ((Valve) value).getElementName();

                    }
                }

                return super.convertValueToString(value);
            }

             public boolean isCellResizable(Object cell)
              {
                 return !getModel().isVertex(cell);
              }
        };

        _graph.addListener(mxEvent.MOVE_CELLS, new mxIEventListener()
        {
            @Override
            public void invoke(Object sender, mxEventObject mxevt) {

                Object[] cells =  (Object[]) mxevt.getProperty("cells");
                Point x = (Point) mxevt.getProperty("location");
                Double dx = (Double) mxevt.getProperty("dx");
                Double dy = (Double) mxevt.getProperty("dy");
            }
        });

        setDefaultConnector();

        _graphComponent=new mxGraphComponent(_graph);
        _graphComponent.setPreferredSize(new Dimension(600, 400));
        this.add(_graphComponent);

        _graph.setVertexLabelsMovable(true);
        _graph.setDisconnectOnMove(false);
        _graph.setConnectableEdges(false);
        _graph.setCellsEditable(false);
        _graph.setResetEdgesOnMove(true);

        _valves=new ArrayList<Valve>();

        _panel.add(new GUIBoardToolBars(this).addFileToolBar());
        _frame.add(new GUIBoardToolBars(this).addPowerElements(), BorderLayout.EAST);
        _frame.add(_panel, BorderLayout.NORTH);

    }

    public mxGraph getGraph(){

        return _graph;
    }

    public mxGraphComponent getGraphComponent(){

        return _graphComponent;

    }

    private void setDefaultConnector() {
        Map<String, Object> connector = new HashMap<String, Object>();
        connector.put(mxConstants.STYLE_ROUNDED, false);
        connector.put(mxConstants.STYLE_ORTHOGONAL, true);
        connector.put(mxConstants.STYLE_EDGE, "elbowEdgeStyle");
        connector.put(mxConstants.STYLE_SHAPE, mxConstants.SHAPE_CONNECTOR);
        connector.put(mxConstants.STYLE_ENDARROW, mxConstants.NONE);


        mxStylesheet connectorStyle = new mxStylesheet();
        connectorStyle.setDefaultEdgeStyle(connector);
        _graph.setStylesheet(connectorStyle);
    }

    public void addValves(Valve valve){

            _valves.add(valve); 
    }

    public ArrayList<Valve> getValves(){

        return _valves;
    }

    public void addToRegistry(String element){
        String nodeXml, objectName;
        mxStencilShape newShape;
        try {
            nodeXml = mxUtils.readFile(element);
            newShape = new mxStencilShape(nodeXml);
            objectName = newShape.getName(); 
            mxGraphics2DCanvas.putShape(objectName, newShape);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public GUIBoard(LayoutManager arg0) {
        super(arg0);
        // TODO Auto-generated constructor stub
    }

    public GUIBoard(boolean arg0) {
        super(arg0);
        // TODO Auto-generated constructor stub
    }

    public GUIBoard(LayoutManager arg0, boolean arg1) {
        super(arg0, arg1);
        // TODO Auto-generated constructor stub
    }

}

The GUI action is:

package graphicalUserInterface;

import java.awt.MouseInfo;
import java.awt.event.ActionEvent;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionAdapter;
import java.awt.event.MouseMotionListener;
import java.io.IOException;
import java.io.UnsupportedEncodingException;

import javax.swing.AbstractAction;

import org.w3c.dom.Document;

import com.mxgraph.io.mxCodec;
import com.mxgraph.io.mxCodecRegistry;
import com.mxgraph.io.mxObjectCodec;
import com.mxgraph.model.mxCell;
import com.mxgraph.model.mxGeometry;
import com.mxgraph.util.mxUtils;
import com.mxgraph.util.mxXmlUtils;

import netElements.Valve;

public class GUIBoardActions {

    public GUIBoardActions() {
        // TODO Auto-generated constructor stub
    }

    public static class NewNetwork extends AbstractAction {

        private GUIBoard _newNDB;
        public NewNetwork(GUIBoard ndb) {
            _newNDB=ndb;
        }

        @Override
        public void actionPerformed(ActionEvent e) {

        }

    }

    public static class OpenNetwork extends AbstractAction {

        /**
         * 
         */
        private static final long serialVersionUID = 8166859573134106478L;
        private GUIBoard _openNDB;
        private Document document;
        mxCodec codec ;
        public OpenNetwork(GUIBoard ndb) {
            _openNDB=ndb;
            mxCodecRegistry.addPackage(Valve.class.getPackage().toString());
            mxCodecRegistry.register(new mxObjectCodec(new Valve()));

        }

        @Override
        public void actionPerformed(ActionEvent aevt) {
            mxCodecRegistry.addPackage(Valve.class.getPackage().toString());
            mxCodecRegistry.register(new mxObjectCodec(new Valve()));

            try {
                document = mxXmlUtils.parseXml(mxUtils.readFile("C:\\test graph/file.xml"));
                codec = new mxCodec(document);
                codec.decode(document.getDocumentElement(), _openNDB.getGraph().getModel());
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            _openNDB.getGraph().getModel().beginUpdate();
            Object[] cells;
            try
            {
                cells= _openNDB.getGraph().getChildCells(_openNDB.getGraph().getDefaultParent(), true, true);

            }
            finally
            {
                _openNDB.getGraph().getModel().endUpdate();
            }

            _openNDB.getGraph().addCells(cells);
            for (Object c : cells) {
                mxCell cell = (mxCell) c;
                if (cell.isVertex()) {
                    if (cell.getValue() instanceof Valve) {
                        Valve valve=(Valve) cell.getValue();
                        _openNDB.addValves(valve);

                    }
                }
            }

        }

    }


    public static class SaveNetwork extends AbstractAction {

        /**
         * 
         */
        private static final long serialVersionUID = 4757526430199667311L;
        private GUIBoard _saveNDB;

        public SaveNetwork(GUIBoard ndb) {
            _saveNDB=ndb;
        }

        @Override
        public void actionPerformed(ActionEvent aevt) {
            mxCodec codec = new mxCodec();
            try {

                String xml2 = mxUtils.getPrettyXml(codec.encode(_saveNDB.getGraph().getModel()));

                mxUtils.writeFile(xml2, "C:\\test graph/file.xml");


            } catch (UnsupportedEncodingException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }   
        }

    }

    public static class AddNewValve extends AbstractAction {

        /**
         * 
         */
        private static final long serialVersionUID = 4187443683391653845L;
        private GUIBoard _valveNDB;
        private MouseMotionListener _boardMotionListener;
        private MouseListener _boardListener;

        public AddNewValve(GUIBoard ndb){
            _valveNDB=ndb;

        }

        @Override
        public void actionPerformed(ActionEvent aevt) {

            Valve v = new Valve();
            v.setElementNumber(_valveNDB.getValves().size()+1);
            v.setElementName("V"+v.getElementNumber());
            v.setElementStyleName("VALVE"+v.getElementNumber());
            v.setElementStyle(_valveNDB.getGraph());            

            _valveNDB.addValves(v);

            mxCell vCell;
            _valveNDB.getGraph().getModel().beginUpdate();
            try
            {
                vCell=(mxCell) _valveNDB.getGraph().insertVertex(_valveNDB.getGraph().getDefaultParent(), null, v, MouseInfo.getPointerInfo().getLocation().x,MouseInfo.getPointerInfo().getLocation().y, 80, 30,v.getElementStyleString());

            }
            finally
            {
                _valveNDB.getGraph().getModel().endUpdate();
            }

            vCell.setAttribute("Name", v.getElementName());
            vCell.setConnectable(false);


            _valveNDB.getGraphComponent().getGraphControl().addMouseMotionListener(_boardMotionListener=new MouseMotionAdapter() {


                @Override
                public void mouseDragged(MouseEvent mevt) {
                    // TODO Auto-generated method stub

                }

                @Override
                public void mouseMoved(MouseEvent mevt) {
                    vCell.setGeometry(new mxGeometry(mevt.getX(),mevt.getY(),80,30));
                    _valveNDB.getGraph().refresh();

                }

            });

            _valveNDB.getGraphComponent().getGraphControl().addMouseListener(_boardListener=new MouseListener() {

                @Override
                public void mouseReleased(MouseEvent mevt) {
                    // TODO Auto-generated method stub

                }

                @Override
                public void mousePressed(MouseEvent mevt) {
                    // TODO Auto-generated method stub

                }

                @Override
                public void mouseExited(MouseEvent mevt) {
                    // TODO Auto-generated method stub

                }

                @Override
                public void mouseEntered(MouseEvent mevt) {
                    // TODO Auto-generated method stub

                }

                @Override
                public void mouseClicked(MouseEvent mevt) {
                    _valveNDB.getGraphComponent().getGraphControl().removeMouseListener(_boardListener);
                    _valveNDB.getGraphComponent().getGraphControl().removeMouseMotionListener(_boardMotionListener);

                }
            });

        }       
    }


}

Here is the toolbar code:

package graphicalUserInterface;

import java.awt.Color;
import java.awt.event.ActionEvent;

import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.BorderFactory;
import javax.swing.ImageIcon;
import javax.swing.JToolBar;
import javax.swing.UIManager;

import graphicalUserInterface.GUIBoardActions.*;

public class GUIBoardToolBars extends JToolBar {

    /**
     * 
     */
    private static final long serialVersionUID = 7241903583392004921L;


    GUIBoard _drawingBoard;
    //JToolBar _fileToolBar;

    public GUIBoardToolBars(GUIBoard ndb) {
        _drawingBoard=ndb;
        //_fileToolBar=new JToolBar();
    }

    public JToolBar addFileToolBar(){
        JToolBar fileToolBar=new JToolBar();
        fileToolBar.setBorder(BorderFactory.createCompoundBorder(BorderFactory.createEmptyBorder(3, 3, 3, 3), getBorder()));
        fileToolBar.setFloatable(false);
        fileToolBar.setAlignmentX(0);
        UIManager.put("ToolTip.background", Color.TRANSLUCENT);


        fileToolBar.add(addNewComponent("New", new NewNetwork(_drawingBoard), new ImageIcon("Icon/new.gif"))).setToolTipText("New");

        fileToolBar.add(addNewComponent("Open", new OpenNetwork(_drawingBoard), new ImageIcon("Icon/open.gif"))).setToolTipText("Open");

        fileToolBar.add(addNewComponent("Save", new SaveNetwork(_drawingBoard), new ImageIcon("Icon/save.gif"))).setToolTipText("Save");
        //JButton newFileToolBar=new JButton();
        //newFileToolBar.setActionCommand("newFileToolBar");
        //newFileToolBar.setIcon(new ImageIcon("Image/new.gif"));
        //newFileToolBar.setToolTipText("New");
        //fileToolBar.add(newFileToolBar);
        return fileToolBar;
    }

    public JToolBar addPowerElements(){
        JToolBar powerElements=new JToolBar(VERTICAL);
        powerElements.setBorder(BorderFactory.createCompoundBorder(BorderFactory.createEmptyBorder(3,3,3,3), getBorder()));
        powerElements.setFloatable(false);


        powerElements.add(addNewComponent("Valve", new AddNewValve(_drawingBoard), new ImageIcon("Icon/valve1.png"))).setToolTipText("Valve");

        return powerElements;
    }

    @SuppressWarnings("serial")
    public Action addNewComponent(String name, Action componentAction, ImageIcon icon){

        AbstractAction newComponent=new AbstractAction(name,(icon!=null) ? icon : null){

            public void actionPerformed(ActionEvent e)
            {
                componentAction.actionPerformed(new ActionEvent(_drawingBoard.getGraphComponent(),e.getID(),e.getActionCommand()));
            }
        };
        icon.setDescription(name);      
        return newComponent;

    }

    public GUIBoardToolBars(int arg0) {
        super(arg0);
        // TODO Auto-generated constructor stub
    }

    public GUIBoardToolBars(String arg0) {
        super(arg0);
        // TODO Auto-generated constructor stub
    }

    public GUIBoardToolBars(String arg0, int arg1) {
        super(arg0, arg1);
        // TODO Auto-generated constructor stub
    }

}

And finally the custom object class:

package netElements;

import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;

import com.mxgraph.model.mxCell;
import com.mxgraph.util.mxConstants;
import com.mxgraph.view.mxGraph;
import com.mxgraph.view.mxStylesheet;

public class Valve implements BasicPropertiesOfElement, Serializable {

    /**
     * 
     */
    private static final long serialVersionUID = 6425822395370778513L;
    private mxCell _valveCell;
    private transient mxStylesheet _valveStyleSheet;
    protected int _valveNumber;
    private double _valveX, _valveY, _valveRotationalAngle=0;
    private String _valveName, _valveStyleName, _valveStyleString="";

    public Valve() {

    }

    public void setElementStyleName(String styleName) {

        _valveStyleName=styleName;
    }

    public String getElementStyleName() {

        return _valveStyleName;
    }

    public void setElementStyle(mxGraph g) {

        Map<String, Object> transProperties;

        _valveStyleSheet = g.getStylesheet();
        transProperties = new HashMap<String, Object>();
        transProperties.put(mxConstants.STYLE_SHAPE, "valve");
        transProperties.put(mxConstants.STYLE_STROKECOLOR, "black");
        transProperties.put(mxConstants.STYLE_ROTATION, _valveRotationalAngle);
        transProperties.put(mxConstants.STYLE_VERTICAL_LABEL_POSITION, mxConstants.ALIGN_TOP);
        _valveStyleSheet.putCellStyle(_valveStyleName, transProperties);

        this.setElementStyleString(transProperties);

    }

    public mxStylesheet getElementStyle() {

        return this._valveStyleSheet;
    }

    public void setElementStyleString(Map<String, Object> transProperties) {

        transProperties.entrySet().stream().forEach(entry ->
        _valveStyleString+=entry.getKey()+"="+entry.getValue().toString()+";");
    }

    public String getElementStyleString() {

        return _valveStyleString;

    }



    @Override
    public void setElementRotationalAngle(double angle) {
        // TODO Auto-generated method stub
        _valveRotationalAngle=angle;

    }



    @Override
    public double getElementRotationalAngle() {
        // TODO Auto-generated method stub
        return _valveRotationalAngle;
    }


    @Override
    public void setElementNumber(int elementNumber) {
        // TODO Auto-generated method stub
        _valveNumber=elementNumber;

    }



    @Override
    public int getElementNumber() {
        // TODO Auto-generated method stub
        return _valveNumber;
    }



    @Override
    public void setElementName(String elementName) {
        // TODO Auto-generated method stub
        _valveName=elementName;

    }



    @Override
    public String getElementName() {
        // TODO Auto-generated method stub
        return _valveName;
    }

}

I checked the xml file and found that the properties of the custom object (Here named Valve) is not shown. Based on the example here, the custom object should be registered in the codedc and the rest would be handled by the JGraph. I do not know what to do or which method should be overridden to save the properties of the custom object along with the cell. Any help would be really appreciated.

Solution

  • I found the solution. The object properties in the object class (here Valve) should be the same as the getter/setter method name. For example, the variable (property) with the name "_valveName" should match its getter/setter method. Here the getter/setter methods for this variable are:
    public void setElementName(String elementName) public String getElementName() Which are not the same as variable name. So, by changing either the variable name or getter/setter method names the problem get solved. Here is the revised custom object class:

    package netElements;

import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;

import com.mxgraph.model.mxCell;
import com.mxgraph.util.mxConstants;
import com.mxgraph.view.mxGraph;
import com.mxgraph.view.mxStylesheet;

public class Valve implements Serializable {

    /**
     * 
     */
    private static final long serialVersionUID = 6425822395370778513L;
    protected int valveNumber;
    protected String valveName;
    private transient mxStylesheet valveStyleSheet;
    private mxCell _valveCell;
    private double _valveX, _valveY, valveRotationalAngle=0;
    protected String valveStyleName, valveStyleString="";

    public Valve() 
    {   
    }

    public void setValveNumber(int elementNumber) {
        // TODO Auto-generated method stub
        valveNumber=elementNumber;

    }

    public int getValveNumber() {
        // TODO Auto-generated method stub
        return valveNumber;
    }

    public void setValveStyleName(String styleName) {

        valveStyleName=styleName;
    }

    public String getValveStyleName() {

        return valveStyleName;
    }

    public void setValveStyle(mxGraph g) {

        Map<String, Object> transProperties;

        valveStyleSheet = g.getStylesheet();
        transProperties = new HashMap<String, Object>();
        transProperties.put(mxConstants.STYLE_SHAPE, "valve");
        transProperties.put(mxConstants.STYLE_STROKECOLOR, "black");
        transProperties.put(mxConstants.STYLE_ROTATION, valveRotationalAngle);
        transProperties.put(mxConstants.STYLE_VERTICAL_LABEL_POSITION, mxConstants.ALIGN_TOP);
        valveStyleSheet.putCellStyle(valveStyleName, transProperties);

        this.setValveStyleString(transProperties);

    }

    public mxStylesheet getValveStyle() {

        return this.valveStyleSheet;
    }

    public void setValveStyleString(Map<String, Object> transProperties) {

        transProperties.entrySet().stream().forEach(entry ->
        valveStyleString+=entry.getKey()+"="+entry.getValue().toString()+";");
    }

    public String getValveStyleString() {

        return valveStyleString;

    }

    public void setValveRotationalAngle(double angle) {
        // TODO Auto-generated method stub
        valveRotationalAngle=angle;

    }

    public double getValveRotationalAngle() {
        // TODO Auto-generated method stub
        return valveRotationalAngle;
    }


    public void setValveName(String elementName) {
        // TODO Auto-generated method stub
        valveName=elementName;

    }

    public String getValveName() {
        // TODO Auto-generated method stub
        return this.valveName;
    }

}

    The entire example can be found here.