The TreeSDMModel2 class

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To display the data model of a tree in a diagram component, you must write a data model that transforms the tree data into an SDM model. In this example, the model is implemented by a subclass of IlvBasicSDMModel, as shown in the following code example.

public class TreeSDMModel2 extends IlvBasicSDMModel
{
...

This SDM model will use the tree nodes taken from the JTree model directly, instead of implementing a new class to represent the nodes of the graph. This approach has the advantage of saving one object allocation for each node.

However, a new class is needed for the links, because there is no object that represents a parent-child relationship in a JTree model.

Reference to the tree model

The TreeSDMModel2 class keeps a reference to the tree model, as shown in the following code example.

private TreeModel treeModel;
  private ArrayList links = new ArrayList();

  public TreeSDMModel2(TreeModel treeModel)
  {
    this.treeModel = treeModel;
    
    createLinks(treeModel.getRoot());
  }

Method for creating links

The createLinks method creates the parent-child links and stores them in a list, as shown in the following code example.

private void createLinks(Object treeNode)
  {
    for(int i = 0; i < treeModel.getChildCount(treeNode); i++){
      Object childNode = treeModel.getChild(treeNode, i);
      links.add(new TreeLink(treeNode, childNode));
      
      createLinks(childNode);
    }
  }

Method for retrieving all nodes and links

The getObjects method (shown in the following code example) returns all the nodes of the tree recursively, and also returns the links that have been created in the constructor. Note that, in this variant, the data model is flat, that is, the tree hierarchy does not translate into subgraphs, so all nodes and links are at the same level in the SDM model.

Retrieving nodes and links

public Enumeration getObjects()
  {
    Vector v = new Vector();
    
    getTreeNodes(treeModel.getRoot(), v);
    
    for (int i = 0; i < links.size(); i++) {
      v.addElement(links.get(i));
    }
    
    return v.elements();
  }
  
  private void getTreeNodes(Object parentNode, Vector v)
  {
    v.addElement(parentNode);
    for(int i = 0; i < treeModel.getChildCount(parentNode); i++){
      getTreeNodes(treeModel.getChild(parentNode, i), v);
    }
  }

Methods of the SDM model interface

The methods of the SDM model interface are implemented directly in the subclass of IlvBasicSDMModel, instead of being implemented in the node and link classes, see the following code example.

Implementing the SDM model interface

  public String getTag(Object obj)
  {
    if(isLink(obj))
      return "treelink";
    else
      return "treenode";
  }

  public boolean isLink(Object obj)
  {
    return obj instanceof TreeLink;
  }

  public Object getFrom(Object link)
  {
    return ((TreeLink)link).getParentNode();
  }

  public Object getTo(Object link)
  {
    return ((TreeLink)link).getChildNode();
  }

  public Object getObjectProperty(Object object, String property)
  {
    if(object instanceof DefaultMutableTreeNode){
      if(property.equals("userObject")){
        return ((DefaultMutableTreeNode)object).getUserObject();
      }
      if(property.equals("CSSclass") &&        
         ((DefaultMutableTreeNode)object).getParent() != null){
        return  
        ((DefaultMutableTreeNode)((DefaultMutableTreeNode)object).
             getParent()).getUserObject();
      }
    }
    return null;
  }
  
  public String[] getObjectPropertyNames(Object object)
  {
    if(object instanceof DefaultMutableTreeNode)
      return new String[] { "userObject", "CSSclass" };
    else
      return new String[0];
  }

Current section

NonJavaBeans example: basic model variant