关于dhtmlxtree的问题

看网上说可以通过setXMLAutoLoading 异步加载，我代码如下： tree.xml
<?xml version="1.0" encoding="UTF-8"?>
<tree id="0">
<item text="oooo" id="a0001" child="1">
</item>
</tree>tree2.xml
<?xml version="1.0" encoding="UTF-8"?>
<tree id="a0001">
<item id="rrr" text="rrr">
</item>
</tree>tree2的ID和tree.xml的item的ID一样my.jsp <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
%>
<link rel="stylesheet" href="<%=path%>/dhtmlxtree/codebase/dhtmlxtree.css" type="text/css">
<SCRIPT LANGUAGE="JavaScript" src="<%=path%>/dhtmlxtree/codebase/dhtmlxcommon.js"></SCRIPT>
<SCRIPT LANGUAGE="JavaScript" src="<%=path%>/dhtmlxtree/codebase/dhtmlxtree.js"></SCRIPT>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>My JSP 'index.jsp' starting page</title>
  </head>
  
  <body>
<TABLE style="width:100%;height:100%">
<TR>
<TD>
  <div id="tree_swjg" style="width:100%; height:100%;"></div>
</TD>
</TR>
</TABLE><script type="text/javascript"> tree=new dhtmlXTreeObject("tree_swjg","100%","100%",0);
tree.setImagePath("dhtmlxtree/codebase/imgs/csh_winstyle/");
tree.enableTreeLines(true);
tree.loadXML("tree.xml");
tree.setXMLAutoLoading("tree2.xml");

</script>
</body>
</html>想tree2.xml添加到tree.xml中，但不成功！
不知道为什么，