// 获取一个网站上的链接,filter 用来过滤链接
  public static Set<String> extracLinks(String url, NodeFilter filter) {
    Set<String> links = new HashSet<String>();
    try {
      Parser parser = new Parser(url);
      parser.setEncoding("UTF-8");

      @SuppressWarnings("serial")
      NodeFilter frameFilter =
          new NodeFilter() {
            public boolean accept(Node node) {
              if (node.getText().startsWith("frame src=")) {
                return true;
              } else {
                return false;
              }
            }
          };

      OrFilter linkFilter = new OrFilter(new NodeClassFilter(LinkTag.class), frameFilter);

      NodeList list = parser.extractAllNodesThatMatch(linkFilter);

      System.out.println("length=" + list.size());

      for (int i = 0; i < list.size(); i++) {
        Node tag = list.elementAt(i);

        if (tag instanceof LinkTag) { // <a> 标签
          LinkTag link = (LinkTag) tag;
          String linkUrl = link.getLink(); // URL

          /*
           * if (filter.accept(linkUrl)) { links.add(linkUrl); }
           */

          System.out.println("linkUrl=" + linkUrl);

          if (filter.accept(tag)) {
            links.add(linkUrl);
          }
        } else { // <frame> 标签
          // 提取 frame 里 src 属性的链接,如 <frame src="test.html"/>
          String frame = tag.getText();
          int start = frame.indexOf("src=");
          frame = frame.substring(start);
          int end = frame.indexOf(" ");

          if (end == -1) {
            end = frame.indexOf(">");
          }

          String frameUrl = frame.substring(5, end - 1);
          // if (filter.accept(frameUrl)) {
          // links.add(frameUrl);
          // }

          System.out.println("frameUrl=" + frameUrl);

          if (filter.accept(tag)) {
            links.add(frameUrl);
          }
        }
      }

      /*
       * NodeFilter filter = new TagNameFilter("DIV"); NodeList nodes =
       * parser.extractAllNodesThatMatch(filter); if(nodes!=null) { for
       * (int i = 0; i < nodes.size(); i++) { Node textnode = (Node)
       * nodes.elementAt(i);
       * System.out.println("getText:"+textnode.getText());
       * System.out.println
       * ("================================================="); } }
       */
      /*
       * for(NodeIterator i = parser.elements (); i.hasMoreNodes(); ) {
       * Node node = i.nextNode();
       * System.out.println("getText:"+node.getText());
       * System.out.println("getPlainText:"+node.toPlainTextString());
       * System.out.println("toHtml:"+node.toHtml());
       * System.out.println("toHtml(true):"+node.toHtml(true));
       * System.out.println("toHtml(false):"+node.toHtml(false));
       * System.out.println("toString:"+node.toString());
       * System.out.println
       * ("================================================="); }
       */

      /*
       * TextExtractingVisitor visitor = new TextExtractingVisitor();
       * parser.visitAllNodesWith(visitor); String textInPage =
       * visitor.getExtractedText(); System.out.println(textInPage);
       */

    } catch (ParserException e) {
      e.printStackTrace();
    }
    return links;
  }