Error with JAXBContext when converting an inputStream to an object

[wonderbox]

I have found an Error with JAXBContext when converting an inputStream to an object the error is :
 
But my inputStream is already encoded in UTF-8  !!!! ???

javax.xml.bind.UnmarshalException
 - with linked exception:
[com.sun.org.apache.xerces.internal.impl.io.MalformedByteSequenceException: Invalid byte 2 of 2-byte UTF-8 sequence.]