我获取的请求为什么和大家不一样

org.apache.catalina.connector.RequestFacade@5cca7f61

严重: Servlet.service() for servlet [wechatServerlet] in context with path [/wechat] threw exception

java.lang.NullPointerException

at wechat.wechat_serverlet.doPost(wechat_serverlet.java:40)

@Override

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

req.setCharacterEncoding("UTF-8");

resp.setCharacterEncoding("UTF-8");

System.out.println("weiqing.cao " + req);

PrintWriter out = resp.getWriter();

try {

Map<String, String> map = wechat_message.xmlToMap(req);

String toUserName = map.get("ToUserName");

我的控制台打印出来的不是xml，这里获取不到标签报了空指针什么原因？