xStream XML转换为对象有错误 有人帮忙看一下吗

Exception in thread "Thread-7" com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter$UnknownFieldException: No such field com.xlpayment.nucc.entity.MsgHeader.SignSN
---- Debugging information ----
field : SignSN
class : com.xlpayment.nucc.entity.MsgHeader
required-type : com.xlpayment.nucc.entity.MsgHeader
converter-type : com.thoughtworks.xstream.converters.reflection.ReflectionConverter
path : /root/MsgHeader/SignSN
class[1] : com.xlpayment.nucc.entity.AuthDataEntity

version : null

at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.determineType(AbstractReflectionConverter.java:453)
at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.doUnmarshal(AbstractReflectionConverter.java:294)
at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.unmarshal(AbstractReflectionConverter.java:234)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50)
at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.doUnmarshal(AbstractReflectionConverter.java:322)
at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.unmarshal(AbstractReflectionConverter.java:234)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:134)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:32)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1058)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1042)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:913)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:904)
at com.xlpayment.nucc.service.XstreamManagerServiceImpl.receiveReqBankDataXML(XstreamManagerServiceImpl.java:58)
at com.xlpayment.nucc.business.NuccTransBusi.AuthAndSign(NuccTransBusi.java:22)
at com.xlpayment.nucc.websocket.NuccServer.run(NuccServer.java

header类
private String SndDt;
private String MsgTp;
private String IssrId;
private String Drctn;
private String SignSn;
private String NcrptnSn;
private String DgtlEnvlp;