FULL PRODUCT VERSION :
XCode

ADDITIONAL OS VERSION INFORMATION :
MacOC Sierra (latest)

A DESCRIPTION OF THE PROBLEM :
Hi,

(1) your http://java.sun.com/xml/jaxp/properties/schemaLanguage is corrupt;

(2) IMHO, your XSD-file handling is buggy: the XSD-file is put at a default location without the possibility of changing the location.

Best,

Simon


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
package xml;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.BufferedReader;
import java.io.IOException;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
import javax.xml.bind.SchemaOutputResolver;

import javax.xml.transform.Result;
import javax.xml.transform.stream.StreamResult;


public interface XML {
    
    public static final String namespaceURL =
        "http://www.ti.bfh.ch/fileadmin/modules/BTI7055-de.xml";
    
    public default void writeXMLdoc (String xmldocfilepath, String xsdfilepath) {
        try {
            JAXBContext context = JAXBContext.newInstance(this.getClass());
            Marshaller marshaller = context.createMarshaller();
            marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
            marshaller.setProperty(Marshaller.JAXB_SCHEMA_LOCATION,
                                   namespaceURL+" "+xsdfilepath);
            marshaller.marshal(this, new File(xmldocfilepath));
            //marshaller.marshal(this, System.out);
            writeXSD(xsdfilepath);
        } catch (Exception e) { e.printStackTrace(); }
    }
    
    public default void writeXSD (String xsdfilepath) {
        class LocalFileSchemaResolver extends SchemaOutputResolver {
            // by the way, this is an inner (local) class ;-)
            private File f;
            LocalFileSchemaResolver (File f) { this.f = f; }
            public Result createOutput (String namespaceURI,
                                        String fileName) throws IOException {
                StreamResult sr = new StreamResult(
                                    new OutputStreamWriter(
                                        new FileOutputStream(fileName), "UTF-8"));
                sr.setSystemId(f.toURI().toURL().toString());
                return sr;
            }
        }
        try {
            JAXBContext context = JAXBContext.newInstance(this.getClass());
            context.generateSchema(new LocalFileSchemaResolver(new File(xsdfilepath)));
        } catch (Exception e) { e.printStackTrace(); }
    }
    
    public static Object xmldoc2object (String xmldocfilepath, Class objectclass) {
        Object object = null;
        try {
            JAXBContext context = JAXBContext.newInstance(objectclass);
            Unmarshaller unmarshaller = context.createUnmarshaller();
            object = objectclass.cast(unmarshaller.unmarshal(
                        new BufferedReader(
                            new InputStreamReader(
                                new FileInputStream(xmldocfilepath), "UTF-8"))));
        } catch (Exception e) { e.printStackTrace(); }
        return object;
    }

}
=========================================================
package xml;

import java.io.StringReader;

import java.nio.charset.StandardCharsets;

import java.nio.file.Files;
import java.nio.file.Paths;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;

import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.ErrorHandler;


public class XMLDOMParsing {
    
    private Document xmldom = null;
    public Document getDOM () { return xmldom; }

    public XMLDOMParsing (String xmlfilepathstr) {
        String xmldoc = file2str(xmlfilepathstr);
               xmldom = XML2DOM(xmldoc);
    }

    private String file2str (String filepathstr) {
        String str = "";
        try {
            str = new String(Files.readAllBytes(Paths.get(filepathstr)),
                                StandardCharsets.UTF_8);
        } catch (Exception e) { e.printStackTrace(); }
        return str;
    }
    
    private Document XML2DOM (String xmldoc) {
        DocumentBuilderFactory dbf =
        DocumentBuilderFactory.newInstance();
        // START: required for XML-documents with an attributed XML-schema
        //final String JAXP_SCHEMA_LANGUAGE =
        // "http://java.sun.com/xml/jaxp/properties/schemaLanguage";
        //final String W3C_XML_SCHEMA =
        // "http://www.w3.org/2001/XMLSchema";
        //dbf.setNamespaceAware(true);
        //dbf.setValidating(true);
        //dbf.setAttribute(JAXP_SCHEMA_LANGUAGE, W3C_XML_SCHEMA);
        // END: required for XML-documents with an attributed XML-schema
        Document xmldom = null;
        try {
            DocumentBuilder db = dbf.newDocumentBuilder();
            db.setErrorHandler(new SimpleErrorHandler());
            InputSource src = new InputSource(new StringReader(xmldoc));
            src.setEncoding("UTF-8"); // StandardCharsets.UTF_8 doesn't work
            xmldom = db.parse(src);
        } catch (Exception e) { e.printStackTrace(); }
        return xmldom;
    }
    
    private class SimpleErrorHandler implements ErrorHandler {
        public void warning(SAXParseException e) throws SAXException {
            System.out.println(e.getMessage());
        }
        public void error(SAXParseException e) throws SAXException {
            System.out.println(e.getMessage());
        }
        public void fatalError(SAXParseException e) throws SAXException {
            System.out.println(e.getMessage());
        }
    }
    
}
---------- END SOURCE ----------