JQUERY TREE

要使用jquery.treeview.js，当然第一步是要把它下载下来，放入自己的工程中，然后在页面文件中引进 jquery.js,jquery.cookie.js,jquery.treeview.js,jquery.treeview.async.js四个 库文件，其中最后一个是要使用异步加载结点的时候，要用到的，我的项目中已经用到了这个功能，在初始化树的时候，只加载顶层的数据，当点击顶层结点的时 候，才会去加载下一层的结点，所有的数据都是通过ajax去后台取得到数据。

        将库文件引入后，下一步就是要定义一个列表UL:如这样：
<ul id="ProductTypes">
        </ul>
树数据将会加载到这个UL里面
<script type="text/javascript">
$(document).ready(function(){
//alert('ready');
$("#ProductTypes").treeview({
   url: "/FetchProductTypeServlet"
});
//alert('ready111');
});
</script>
这里面的意思就是当文档加载完成后，向后台FetchProductTypeServlet获取数据，注意后台输出的数据必须是json格式的数据。

下一步就是后台FetchProductTypeServlet的数据输出部分了：

response.setHeader("Cache-Control", "no-cache");
response.setContentType("text/json;charset=UTF-8");
try {
   request.setCharacterEncoding("utf-8");
} catch (UnsupportedEncodingException e1) {
   e1.printStackTrace();
}
要将contenttype设置为"text/json"，第一次加载初始数据的时候，会向这个FetchProductTypeServlet传递一个 get参数：root=source,所以后台可以判断root参数是否是source,如果是source,则代表是第一次加载数据，如果不是 source,则root参数传递的則是树结点的id.

数据格式如下：
[
{
"text": "1. Pre Lunch (120 min)",
"expanded": true,
"classes": "important",
"children":
[
   {
    "text": "1.1 The State of the Powerdome (30 min)"
   },
    {
    "text": "1.2 The Future of jQuery (30 min)"
   },
    {
    "text": "1.2 jQuery UI - A step to richnessy (60 min)"
   }
]
},
{
"text": "2. Lunch (60 min)"
},
{
"text": "3. After Lunch (120+ min)",
"children":
[
   {
    "text": "3.1 jQuery Calendar Success Story (20 min)"
   },
    {
    "text": "3.2 jQuery and Ruby Web Frameworks (20 min)"
   },
    {
    "text": "3.3 Hey, I Can Do That! (20 min)"
   },
    {
    "text": "3.4 Taconite and Form (20 min)"
   },
    {
    "text": "3.5 Server-side JavaScript with jQuery and AOLserver (20 min)"
   },
    {
    "text": "3.6 The Onion: How to add features without adding features (20 min)",
    "id": "36",
    "hasChildren": true
   },
    {
    "text": "3.7 Visualizations with JavaScript and Canvas (20 min)"
   },
    {
    "text": "3.8 ActiveDOM (20 min)"
   },
    {
    "text": "3.8 Growing jQuery (20 min)"
   }
]
}
]

格式说明：上面的1. Pre Lunch (120 min) 结点中："expanded": true 代表这个结点下的child是展开的，children则是子结点的数据，节点3. After Lunch (120+ min)有8个子结点，其中子结点中有一个结点3.6 The Onion: How to add features without adding features (20 min)，有一个id属性，同时hasChildren:true,表示其下面又有子结点，并且会向FetchProductTypeServlet传递 参数为：root=id值，具体到这里就是root=36,那么点击这个结点的时候，后台就会接收到root=36这个值，然后我们就在具体应用中，通过 数据库查询或者其它方式找到相对应的数据，然后将这些数据构造成treeview所需要的json数据，也即是上面所示格式的数据。

后台FetchProductTypeServlet代码如下：
public class FetchProductTypeServlet extends HttpServlet {

ProdTypeDao prodTypeDao = null;

@Override
public void init() throws ServletException {
// TODO Auto-generated method stub
prodTypeDao = new ProdTypeDao();
super.init();
}

public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
doPost(request,response);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {

response.setHeader("Cache-Control", "no-cache");
response.setContentType("text/json;charset=UTF-8");
try {
   request.setCharacterEncoding("utf-8");
} catch (UnsupportedEncodingException e1) {
   e1.printStackTrace();
}

PrintWriter out = response.getWriter();

String root = request.getParameter("root");
System.out.println("root:"+root);

try {
   String output = generateNodeString(root);
   System.out.println("output======"+output);
   out.print(generateNodeString(root));
} catch (ActionException e) {
   e.printStackTrace();
   RequestDispatcher rd = null;
   request.setAttribute("ActionException", e);
   rd = request.getRequestDispatcher("/common/error.jsp");
   rd.forward(request, response);
}

out.flush();
out.close();
}

private String generateNodeString(String id) throws ActionException { 
if(id == null){
   return "";
}else if(id.equalsIgnoreCase("source")){   
   return generateInitTreeString();
}else{
   return generateTreeChildNodeString(Integer.parseInt(id));
}
}

private String generateTreeChildNodeString(int typeId) throws ActionException{
int typeId_ = typeId ;
Connection conn = null;

//hasSubItem
StringBuilder sb = new StringBuilder();
sb.append("[");

ArrayList<ProdTypeBean> l;
try {
   l = prodTypeDao.fetchSubItem(typeId_);
} catch (ActionException e) {   
   e.printStackTrace();
   throw new ActionException("generateTreeChildNodeString err","generateTreeChildNodeString","generateTreeChildNodeString err");
}
int i = 0;
for(Iterator it = l.iterator();it.hasNext();i++){
   if(i>0){
    sb.append(",");
   }
   ProdTypeBean item = (ProdTypeBean)it.next();
   sb.append(generateNodeString(item));
}

sb.append("]");
return sb.toString();
} 

private String generateLinkString(ProdTypeBean item){
return "<a href='../../CommendProduct?typeId="+item.getPT_ID()+"' target='main' >"+item.getPT_NAME()+"</a>";
}

private String generateNodeString(ProdTypeBean item){
StringBuilder sb = new StringBuilder();
sb.append(" {");
sb.append(" /"text/": /""+generateLinkString(item)+"/"");

try {
   if(prodTypeDao.hasSubItem(item.getPT_ID())){
    sb.append(", /"id/":/""+item.getPT_ID()+"/"");
    sb.append(", /"hasChildren/":true");
   }
} catch (ActionException e) {   
   e.printStackTrace();
   return "{}";
}
sb.append(" }"); 
return sb.toString();
}

private String generateInitTreeString() throws ActionException{
int typeId_ = 0 ;
Connection conn = null;

//hasSubItem
StringBuilder sb = new StringBuilder();
sb.append("[");

ArrayList<ProdTypeBean> l;
try {
   l = prodTypeDao.fetchSubItem(typeId_);
} catch (ActionException e) {   
   e.printStackTrace();
   throw new ActionException("generateInitTreeString err","generateInitTreeString err","generateInitTreeString err");
}
int i = 0;
for(Iterator it = l.iterator();it.hasNext();i++){
   if(i>0){
    sb.append(",");
   }
   ProdTypeBean item = (ProdTypeBean)it.next();
   sb.append(generateNodeString(item));
}

sb.append("]"); 
return sb.toString();
}

}