public static String XMLTOJSON(String XMLContent，String tag)
 {
  XMLSerializer xmlSerializer = new XMLSerializer(); 
  JSON json = xmlSerializer.read(XMLContent);
  JSONObject obj = JSONObject.fromObject(json);
  JSONObject jobj = obj.getJSONObject（tag);

}

注意：取得的jobj不一定是符合json可以简单的处理，当然下面不通用
  JSONArray arr = null;
  if(jobj.isArray()){
   arr = jobj.getJSONArray("subOrderInfoList");
  }else{
   JSONObject obj0 = jobj.getJSONObject("subOrderInfoList");
   arr = JSONArray.fromObject(obj0);
  }