JavaXMLStreamWriter:输出Unicode扩展字符(非BMP)

有谁知道如何char使用Java的XMLStreamWriter 正确输出扩展字符(非BMP,超过1 )？例如,尝试输出Unicode U + 10480 :

import java.io.OutputStreamWriter;
import java.nio.charset.StandardCharsets;

import javax.xml.stream.XMLOutputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamWriter;

public class XmlStreamWriterExtendedCharactersFail {
    public static void main(String[] args) throws XMLStreamException {
        String inlineStr = "inlineStr = ";
        // create string using StringBuilder to avoid Java file encoding confusion:
        String sbStr = new StringBuilder("sbStr = ").appendCodePoint(0x10480).toString();
        assert sbStr.equals(inlineStr);
        System.out.println(sbStr);

        OutputStreamWriter outWriter = new OutputStreamWriter(System.out,
                StandardCharsets.UTF_8.newEncoder());
        XMLStreamWriter writer = XMLOutputFactory.newFactory()
                .createXMLStreamWriter(outWriter);
        writer.writeStartDocument("UTF-8", "1.1");
        writer.writeStartElement("el");
        writer.writeCharacters(sbStr);
        writer.writeEndElement();
        writer.writeEndDocument();
        writer.close();
    }
}

results in:

sbStr = 
sbStr = &＃xd801;&＃xdc80;

Note that &＃xd801;&＃xdc80;是无效的代码点,在使用SAX解析时会导致错误.

预期产量:

sbStr = 
sbStr = 

sbStr = &＃10480; 也会在紧要关头做,但第一个更好.