该程序可以根据从指定的xml文件中读取的有关信息动态的建立一棵树。
1．该树的特点：
1）无限级树结构
 理论上树的深度可以无限，树的深度由xml文件所给的信息确定；
数据加载采用一次加载和动态加载相结合的方法；
每次打开相关页时重新加载树结构，真正的做到了建立树的动态性。
2）复用性
由于这棵树是通过读取xml文件建立的，树的程序代码固定，所以具有很强的复用性。只需要给出xml文件，程序就可以建立对应的树。
3）与用户的交互
由于该程序是用java小程序实现的，所以可以利用java语言中监听事件的类，以响应用户操作。与用户具有更好的交互性。
2．程序结构
这棵树主要有三个类实现：
1） 类TreeNode：该类起辅助作用，用来描述树的数据结构，并提供一些setter，getter函数用来设置树结构的属性。
2） 类IconRender：该类也是一个辅助类，用来设置树节点的图标。并且可以根据树节点的选中状态改变图标。
3） 类AppletTree：该类是建立这棵树的主要类，它继承自Applet并且实现了TreeSelectionListener接口，以用来监听用户操作。树结构由java类JTree显示，我们只需要合理的设定JTree的属性就可以构造出这棵树。而它的属性是通过jdom中的Element读取xml文件提供的。上面已经提到监听用户操作是通过实现TreeSelectionListener接口完成的，但是只监听不响应毫无用处。怎样才能将监听到的用户操作传给相应的类以响应用户的操作呢？这里用的方法是通过URL将参数传递给jsp文件，再由jsp文件传给相应的操作类实现的。
这三个类的代码如下：
1．TreeNode类
public class TreeNode{
private String id;
private String name;
private String link;
public TreeNode(String id,String name,String link){
this.id=id;
this.name=name;
this.link=link;
}
public String getId(){
return id;
}
public void setId(String Id){
this.id=Id;
}
public void setName(String Name){
this.name=Name;
}
public String getName(){
return name;
}
public String toString(){
return name;
}
public String getLink(){
return link;
}
public void setLink(String link){
this.link=link;
}
}
2. IconRender类
import javax.swing.*;
import java.awt.*;
import javax.swing.tree.*;
import javax.swing.tree.DefaultTreeCellRenderer;
IconRender
class extends DefaultTreeCellRenderer {
//创建用于显示的图标
public static final ImageIcon leafSelectedIcon = new ImageIcon("OpenedFolder.ico");
public static final ImageIcon leafUnSelectedIcon = new ImageIcon("closedFolder.ico");
public static final ImageIcon folderOpen = new ImageIcon("OpenedFolder.ico");
public static final ImageIcon folderClose = new ImageIcon("closedFolder.ico");
//设定图标随选中状态的变化
public Component getTreeCellRendererComponent(JTree
tree,Object value,boolean selected，boolean expanded,
boolean leaf, int row,boolean hasFocus)
{
super.getTreeCellRendererComponent(tree,value, selected, expanded, leaf, row, hasFocus);
if (leaf && selected) {
setIcon(IconRender.leafSelectedIcon);
}
else if (leaf) {
setIcon(IconRender.leafUnSelectedIcon);
}
return this;
}
public IconRender() {
super();
if((leafSelectedIcon != null)&&(leafUnSelectedIcon != null))
System.out.println("IconRender:trace");
setLeafIcon(leafUnSelectedIcon);
setOpenIcon(folderOpen);
setClosedIcon(folderClose);
}
}
3．AppletTree类
import javax.swing.event.*;
import java.awt.*;
import java.applet.*;
import javax.swing.*;
import javax.swing.tree.*;
import java.awt.event.*;
import org.jdom.*;
//import org.w3c.dom.NodeList;
import org.jdom.input.*;
import java.io.*;
import java.util.*;
import java.net.*;
import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
import javax.swing.plaf.*;
import javax.swing.plaf.basic.*;
import javax.swing.plaf.metal.*;
import java.io.*;
//import netscape.javascript.*;
class MyWindowListener extends WindowAdapter
{
public void windowClosing(WindowEvent e)
{
System.exit(1);
}
}
public class AppletTree extends Applet implements TreeSelectionListener
{
private JTree tree;
private TreePath path;
private JScrollPane treeView;
private DefaultMutableTreeNode top;
private DefaultMutableTreeNode clicknode;
private String link;
public AppletTree(){
}
MouseListener ml = new MouseAdapter() {
public void mousePressed(MouseEvent e) {
int selRow = tree.getRowForLocation(e.getX(), e.getY());
TreePath selPath = tree.getPathForLocation(e.getX(), e.getY());
if(selRow != -1) {
if(e.getClickCount() == 1) {
System.out.print("点击一次鼠标");
//得到最后一个节点
DefaultMutableTreeNode treeNode = (DefaultMutableTreeNode)selPath.getLastPathComponent();
boolean isLeaf = treeNode.isLeaf();
TreeNode objTreeNode = (TreeNode)treeNode.getUserObject();
System.out.println(isLeaf);
System.out.println(objTreeNode .getName()) ;
System.out.println(objTreeNode .getId()) ;
if(isLeaf)
{//如果为叶子节点就传出去进行查询操作
try
{
getAppletContext().showDocument(new URL("http://127.0.0.1:8080/tree/showDevice.htm"),"f2" );
}
catch(Exception ex)
{
System.out.print(ex);
}
}
}
else if(e.getClickCount() == 2) {
System.out.print("点击两次鼠标");
//getAppletContext().showDocument(new URL("http://www.csdn.net/"));
//myDoubleClick(selRow, selPath);
}
}
}
};
public void start()
{
super.start();
}
public void init(){
try{
super.init();
this.setLayout(new GridLayout(1,1));
tree=createTree(new FileInputStream("e:/example/TreeXML.xml"));
tree.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION);
tree.putClientProperty("JTree.lineStyle","Angled");
tree.setShowsRootHandles(true);
tree.setEditable(true);
tree.addTreeSelectionListener( this );
IconRender render=new IconRender();
tree.setCellRenderer(render);
treeView = new JScrollPane(tree);
//topPanel.add(tree);
this.add(treeView);
tree.addMouseListener(ml);
}catch(Exception e){
e.printStackTrace();
}
}
public JTree createTree(InputStream is){
SAXBuilder builder = new SAXBuilder();
try {
Document doc = builder.build(is);
Element root=doc.getRootElement();
TreeNode rootNode=new
TreeNode(root.getAttributeValue("id"),root.getAttributeValue("name"),root.getAttributeValue("HaveChildren"));
top=new DefaultMutableTreeNode(rootNode);
addNode(root,top);
} catch (Exception ex) {
ex.printStackTrace();
}
//可以在这里改变jtree中连线的颜色
UIManager.put( "Tree.hash", new ColorUIResource(Color.red) );
return new JTree(top);
}
/**
*
* @param e 待加入树中的jdom元素
* @param fatherNode 树节点父亲节点
*/
private void addNode(Element e,DefaultMutableTreeNode fatherNode){
try{
Iterator it=e.getChildren().iterator();
if(!it.hasNext())
return;
while(it.hasNext()){
Element sub=(Element)it.next();
String id=new String(sub.getAttributeValue("id").getBytes(),"GB2312");
String name=new String(sub.getAttributeValue("name").getBytes(),"GB2312");
String link=new String(sub.getAttributeValue("HaveChildren").getBytes(),"GB2312");
System.out.println(id);
System.out.println(name);
System.out.println(link);
TreeNode tempNode=new TreeNode(id,name,link);
DefaultMutableTreeNode node=new DefaultMutableTreeNode(tempNode);
fatherNode.add(node);
if(link.equals("true")){
System.out.println("true~! equal test");
addNode(sub,node);
}
}
}
catch(Exception exp)
{
System.out.println("encoding fail");
}
}
/**
* 根据id,查找树节点,//广度优先
* @param id 节点id
* @param rootNode 树根节点
* @return DefaultMutableTreeNode
*/
private DefaultMutableTreeNode getTreeNode(String id,DefaultMutableTreeNode rootNode){
DefaultMutableTreeNode returnNode=null;
if(rootNode!=null){
Enumeration enum=rootNode.breadthFirstEnumeration();
while(enum.hasMoreElements()){
DefaultMutableTreeNode temp=(DefaultMutableTreeNode)enum.nextElement();
TreeNode node=(TreeNode)temp.getUserObject();
if(node.getId().equals(id)){
returnNode=temp;
break;
}
}
}
return returnNode;
}
public void valueChanged( TreeSelectionEvent event ){
if( event.getSource() == tree ){
path = event.getPath();
clicknode=(DefaultMutableTreeNode)path.getLastPathComponent();
Object uo=clicknode.getUserObject();
if(uo instanceof TreeNode){
TreeNode nd=(TreeNode)clicknode.getUserObject();
link=nd.getLink();
}
}
}
public static void main(String[] args ){
JFrame frame1=new JFrame("test");
AppletTree tree=new AppletTree();
tree.init();
frame1.getContentPane().add(tree);
frame1.setSize(600,600);
frame1.show();
frame1.addWindowListener(new MyWindowListener());
}
} 
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