nodelister.java

随书的代码

import org.jdom.*;
import org.jdom.input.SAXBuilder;
import java.io.IOException;
import java.util.*;


public class NodeLister {

  public static void main(String[] args) {
  
    if (args.length == 0) {
      System.out.println("Usage: java NodeLister URL"); 
      return;
    } 
      
    SAXBuilder builder = new SAXBuilder();
     
    try {
      Document doc = builder.build(args[0]);
      listNodes(doc, 0);      
    }
    // indicates a well-formedness error
    catch (JDOMException e) { 
      System.out.println(args[0] + " is not well-formed.");
      System.out.println(e.getMessage());
    }  
    catch (IOException e) { 
      System.out.println(e);
    }  
  
  }
  
  
  public static void listNodes(Object o, int depth) {
   
    printSpaces(depth);
    
    if (o instanceof Element) {
      Element element = (Element) o;
      System.out.println("Element: " + element.getName());
      List children = element.getContent();
      Iterator iterator = children.iterator();
      while (iterator.hasNext()) {
        Object child = iterator.next();
        listNodes(child, depth+1);
      }
    }
    else if (o instanceof Document) {
      System.out.println("Document");
      Document doc = (Document) o;
      List children = doc.getContent();
      Iterator iterator = children.iterator();
      while (iterator.hasNext()) {
        Object child = iterator.next();
        listNodes(child, depth+1);
      }
    }
    else if (o instanceof Comment) {
      System.out.println("Comment");
    }
    else if (o instanceof CDATA) {
      System.out.println("CDATA section");
      // CDATA is a subclass of Text so this test must come
      // before the test for Text.
    }
    else if (o instanceof Text) {
      System.out.println("Text");
    }
    else if (o instanceof EntityRef) {
      System.out.println("Entity reference");
    }
    else if (o instanceof ProcessingInstruction) {
      System.out.println("Processing Instruction");
    }
    else {  // This really shouldn't happen
      System.out.println("Unexpected type: " + o.getClass());
    }
    
  }
  
  private static void printSpaces(int n) {
    
    for (int i = 0; i < n; i++) {
      System.out.print(' '); 
    }
    
  }

}