实现从 xml 文件读取 DefaultMutableTreeNode 的 JTree

Question

Is it possible to create at JTree without hardcoding every tree node but rather reading in from a xml file and getting the same output as following code will give:

import javax.swing.JFrame;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;

public class test {

test() {
    JFrame f = new JFrame("Swing");
    DefaultMutableTreeNode life = new DefaultMutableTreeNode("Life");
    DefaultMutableTreeNode plants = new DefaultMutableTreeNode("Plants");
    DefaultMutableTreeNode animals = new DefaultMutableTreeNode("Animals");
    DefaultMutableTreeNode cryptogamers = new DefaultMutableTreeNode("Cryptogamers");
    DefaultMutableTreeNode mammals = new DefaultMutableTreeNode("Mammals");
    JTree root = new JTree(life);

    life.add(plants);
    life.add(animals);

    plants.add(cryptogamers);
    animals.add(mammals);

    f.setSize(200, 200);
    f.add(root);
    f.setVisible(true);

    }

public static void main(String[] args) {
    new test();
    }

}

I want to produce the same result but without hardcoding every node by using this XML file I created:

<Biosphere name="Life"> 
<Kingdom name="Plants"> 
<Division name="Cryptogamers"> 
</Division>
</Kingdom>
<Kingdom name="Animals"> 
<Division name="Mammals"> 
</Division>
</Kingdom>
</Biosphere>

Answer 1

If you serialize the tree with XMLEncoder you can produce something like the below. By extension, you can edit it and then deserialize it. That can of course compress well as there's a lot of redundancy. Serialization would look like:

public void serialize(TreeModel model) {
    try (XMLEncoder enc = new XMLEncoder(Files.newOutputStream(Path.of("tree.xml")))) {
        enc.writeObject(model);
    }
    catch(IOException e) {
        e.printStackTrace();    
    }
}

Producing:

<java version="18.0.2.1" class="java.beans.XMLDecoder">
 <object class="javax.swing.tree.DefaultTreeModel">
  <object class="javax.swing.tree.DefaultMutableTreeNode">
   <void property="userObject">
    <string>Life</string>
   </void>
   <void method="add">
    <object class="javax.swing.tree.DefaultMutableTreeNode">
     <void property="userObject">
      <string>Plants</string>
     </void>
     <void method="add">
      <object class="javax.swing.tree.DefaultMutableTreeNode">
       <void property="userObject">
        <string>Cryptogamers</string>
       </void>
      </object>
     </void>
    </object>
   </void>
   <void method="add">
    <object class="javax.swing.tree.DefaultMutableTreeNode">
     <void property="userObject">
      <string>Animals</string>
     </void>
     <void method="add">
      <object class="javax.swing.tree.DefaultMutableTreeNode">
       <void property="userObject">
        <string>Mammals</string>
       </void>
      </object>
     </void>
    </object>
   </void>
  </object>
 </object>
</java>

Answer 2

There are various XML tree representation you can parse an XML document into eg DOM, Xdm, JDOM and build your JTree recursively by recursively processing that XML tree, here is an example using Saxon HE and XdmNode eg

import net.sf.saxon.s9api.Processor;
import net.sf.saxon.s9api.SaxonApiException;
import net.sf.saxon.s9api.XdmNode;

import javax.swing.JFrame;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.MutableTreeNode;
import java.io.File;

public class Main {
    Main(XdmNode inputDoc) {
        JFrame f = new JFrame("Swing");

        JTree root = new JTree(parseXdmTreeToSwingTree((XdmNode)inputDoc.children("*").iterator().next()));



        f.setSize(200, 200);
        f.add(root);
        f.setVisible(true);

    }

    MutableTreeNode parseXdmTreeToSwingTree(XdmNode inputNode) {
        DefaultMutableTreeNode treeNode = new DefaultMutableTreeNode(inputNode.attribute("name"));
        for (XdmNode child : inputNode.children( "*"))
            treeNode.add(parseXdmTreeToSwingTree(child));
        return treeNode;
    }

    public static void main(String[] args) throws SaxonApiException {
        Processor processor = new Processor(true);
        XdmNode inputDoc = processor.newDocumentBuilder().build(new File("sample1.xml"));
        new Main(inputDoc);
    }
}

Saxon HE is on Maven eg

    <dependency>
        <groupId>net.sf.saxon</groupId>
        <artifactId>Saxon-HE</artifactId>
        <version>11.4</version>
    </dependency>

adds the current version 11.4 to your project.