netconf client can not parse RPC message begin with blank characters.

I have a netconf server which sent the RPC-reply begins and ends with new line character 0x0a as following message. sax exception will be thrown. I try to trim the message in the NetconfXMLToMessageDecoder.decode(), the exception disappears.

0a 3c 3f 78 6d 6c 20 76 65 72 73 69 6f 6e 3d 22 31 2e 30 22 20 65 6e 63 6f 64 69 6e 67 3d 22 55 54 46 2d 38 22 3f 3e
......
3c 2f 72 70 63 2d 72 65 70 6c 79 3e 0a

Caused by: org.xml.sax.SAXParseException: The processing instruction target matching "[xX][mM][lL]" is not allowed.
at org.apache.xerces.parsers.DOMParser.parse(Unknown Source)[:]
at org.apache.xerces.jaxp.DocumentBuilderImpl.parse(Unknown Source)[:]
at javax.xml.parsers.DocumentBuilder.parse(Unknown Source)[:2.4.0]
at org.opendaylight.controller.netconf.util.xml.XmlUtil.readXmlToDocument(XmlUtil.java:99)[191:org.opendaylight.controller.netconf-util:0.2.7.Helium-SR2]
at org.opendaylight.controller.netconf.nettyutil.handler.NetconfXMLToMessageDecoder.decode(NetconfXMLToMessageDecoder.java:29)[199:org.opendaylight.controller.netconf-netty-util:0.2.7.Helium-SR2]
at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:249)[203:io.netty.codec:4.0.23.Final]
... 15 more