java获取xml文件指定标签中值

String xm= "<xml><return_code>SUCCESS</return_code><return_msg>OK</return_msg><appid>wx369ed937faecbe06</appid><mch_id>1250008201</mch_id><nonce_str>nIGTNobdVZ8w1MZc</nonce_str><sign>A6B4A3185D6D7388D717C683ECEDD347</sign><result_code>SUCCESS</result_code><prepay_id>wx201803131425278e875626710110333904</prepay_id><trade_type>MWEB</trade_type><mweb_url>https://wx.tenpay.com/cgi-bin/mmpayweb-bin/checkmweb?prepay_id=wx201803131425278e875626710110333904</mweb_url></xml>";
Document doc = DocumentHelper.parseText(xm);//获取xml文件
Element rootel = doc.getRootElement();//获取根目录

String key = rootel.elementText("return_msg")  //通过标签名,获取value值

System.out.println(key );