adding a root node and setting its key explicitely in dynatree

adding a root node and setting its key explicitely in dynatree

hi
i have a requirement which requires me add a root node and set its value which is unique from other nodes in the dynatree.

here is the code i am using to create the tree

$("#catTree").dynatree({
        idPrefix: "sencat_",
        debugLevel: 0,
        clickFolderMode: 1,
        imagePath: "images/icons/",
        minExpandLevel: 2,
       
        ajaxDefaults: {
            cache: false,
            dataType: "json"
        },
       initAjax: {
            url: "../view/leaflets/PersonCategory.jsp",
            mode: "all"
        },
             
        onLazyRead: function(dtnode){
            dtnode.appendAjax({
                    url: "../view/leaflets/PersonCategory.jsp",
                    mode: "all"                   
            });
        },
       
        onActivate: function(dtnode) {
         oncategoryActivate(dtnode.data.key,dtnode.data.title);
        }
        //fx: { height: "toggle", duration: 200 },
        });

and this is the process in jsp

    try {
      pObj = (PersonInterface)list.get("person");
      
        m = new StringBuffer("");
        sens = pObj.getPersonTypes();
       
        if(sens.size() > 0)
        {
       
            m.append("[");
            int i = 0;
            for(Person s : sens)
            {
                String lazy = "";
                i++;
                if(i == 1){
                    m.append("{");
                    m.append("isFolder: true, title:\"<b>All Sensor Types</b>\"},{");
                    }
                else
                    m.append(",{");
               
                    lazy = "isLazy:true,";
                    String name = rep(s.getName());                   
                    m.append(lazy+" isFolder: true, title:\""+name+"\", tooltip:\""+name+"\", key:\""+s.getId()+"\"}");
            }
            m.append("]");
        }
        out.println(m);
    } catch (Exception e) {
        e.printStackTrace();
    }

now i want to add a root node to it and also set its id to 0 or -1, as all the other values will be used by this nodes created in the program.. 

can anyone tell me a procedure to do this.

i have tried to add the root node at the start of other nodes, but its not showing up and also not giving any error.