Java XMLStreamWriter: Unicode extended character output (no BMP)

Question

Does anyone know how to correctly output extended characters (not BMP, more than 1 char ) using Java XMLStreamWriter? For example, trying to output Unicode U + 10480 𐒀 :

 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 = 𐒀"; // 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(); } } 

leads to:

 sbStr = 𐒀 <?xml version="1.1" encoding="UTF-8"?><el>sbStr = &#xd801;&#xdc80;</el> 

Please note that �� are invalid code points and lead to an error when parsing with SAX.

Expected Result:

 sbStr = 𐒀 <?xml version="1.1" encoding="UTF-8"?><el>sbStr = 𐒀</el> 

sbStr = ⣰ will also do this as a last resort, but the first is preferable.

Answer 1

Note that Apache Commons' StringEscapeUtils.escapeXML also has this issue prior to version 3.0.

I created the following wrapper around XMLStreamWriter as a workaround to my problem. It avoids character data using Apache Commons and writes it directly to the underlying Writer .

 import java.io.IOException; import java.io.Writer; import java.nio.CharBuffer; import javax.xml.namespace.NamespaceContext; import javax.xml.stream.FactoryConfigurationError; import javax.xml.stream.XMLOutputFactory; import javax.xml.stream.XMLStreamException; import javax.xml.stream.XMLStreamWriter; import org.apache.commons.lang3.StringEscapeUtils; import org.apache.commons.lang3.text.translate.CharSequenceTranslator; public class UnicodeXMLStreamWriter implements XMLStreamWriter { private XMLStreamWriter xmlSW; private Writer writer; private CharSequenceTranslator characterEscapor = StringEscapeUtils.ESCAPE_XML11; public static UnicodeXMLStreamWriter newInstance(Writer writer) throws XMLStreamException, FactoryConfigurationError { return newInstance(writer, XMLOutputFactory.newFactory()); } public static UnicodeXMLStreamWriter newInstance(Writer writer, XMLOutputFactory factory) throws XMLStreamException { XMLStreamWriter xmlSW = factory.createXMLStreamWriter(writer); return new UnicodeXMLStreamWriter(writer, xmlSW); } public UnicodeXMLStreamWriter(Writer writer, XMLStreamWriter xmlSW) { this.writer = writer; this.xmlSW = xmlSW; } public void writeCharacters(String text) throws XMLStreamException { // finish writing start element xmlSW.writeCharacters(""); xmlSW.flush(); try { characterEscapor.translate(text, writer); } catch (IOException e) { throw new XMLStreamException(e); } } public void writeCharacters(char[] text, int start, int len) throws XMLStreamException { // finish writing start element xmlSW.writeCharacters(""); xmlSW.flush(); try { characterEscapor.translate(CharBuffer.wrap(text, start, len), writer); } catch (IOException e) { throw new XMLStreamException(e); } } //////////////// REMAINING METHODS ARE DELEGATES to xmlSW //////////////// public void writeStartElement(String localName) throws XMLStreamException { xmlSW.writeStartElement(localName); } public void writeStartElement(String namespaceURI, String localName) throws XMLStreamException { xmlSW.writeStartElement(namespaceURI, localName); } public void writeStartElement(String prefix, String localName, String namespaceURI) throws XMLStreamException { xmlSW.writeStartElement(prefix, localName, namespaceURI); } public void writeEmptyElement(String namespaceURI, String localName) throws XMLStreamException { xmlSW.writeEmptyElement(namespaceURI, localName); } public void writeEmptyElement(String prefix, String localName, String namespaceURI) throws XMLStreamException { xmlSW.writeEmptyElement(prefix, localName, namespaceURI); } public void writeEmptyElement(String localName) throws XMLStreamException { xmlSW.writeEmptyElement(localName); } public void writeEndElement() throws XMLStreamException { xmlSW.writeEndElement(); } public void writeEndDocument() throws XMLStreamException { xmlSW.writeEndDocument(); } public void close() throws XMLStreamException { xmlSW.close(); } public void flush() throws XMLStreamException { xmlSW.flush(); } public void writeAttribute(String localName, String value) throws XMLStreamException { xmlSW.writeAttribute(localName, value); } public void writeAttribute(String prefix, String namespaceURI, String localName, String value) throws XMLStreamException { xmlSW.writeAttribute(prefix, namespaceURI, localName, value); } public void writeAttribute(String namespaceURI, String localName, String value) throws XMLStreamException { xmlSW.writeAttribute(namespaceURI, localName, value); } public void writeNamespace(String prefix, String namespaceURI) throws XMLStreamException { xmlSW.writeNamespace(prefix, namespaceURI); } public void writeDefaultNamespace(String namespaceURI) throws XMLStreamException { xmlSW.writeDefaultNamespace(namespaceURI); } public void writeComment(String data) throws XMLStreamException { xmlSW.writeComment(data); } public void writeProcessingInstruction(String target) throws XMLStreamException { xmlSW.writeProcessingInstruction(target); } public void writeProcessingInstruction(String target, String data) throws XMLStreamException { xmlSW.writeProcessingInstruction(target, data); } public void writeCData(String data) throws XMLStreamException { xmlSW.writeCData(data); } public void writeDTD(String dtd) throws XMLStreamException { xmlSW.writeDTD(dtd); } public void writeEntityRef(String name) throws XMLStreamException { xmlSW.writeEntityRef(name); } public void writeStartDocument() throws XMLStreamException { xmlSW.writeStartDocument(); } public void writeStartDocument(String version) throws XMLStreamException { xmlSW.writeStartDocument(version); } public void writeStartDocument(String encoding, String version) throws XMLStreamException { xmlSW.writeStartDocument(encoding, version); } public String getPrefix(String uri) throws XMLStreamException { return xmlSW.getPrefix(uri); } public void setPrefix(String prefix, String uri) throws XMLStreamException { xmlSW.setPrefix(prefix, uri); } public void setDefaultNamespace(String uri) throws XMLStreamException { xmlSW.setDefaultNamespace(uri); } public void setNamespaceContext(NamespaceContext context) throws XMLStreamException { xmlSW.setNamespaceContext(context); } public NamespaceContext getNamespaceContext() { return xmlSW.getNamespaceContext(); } public Object getProperty(String name) throws IllegalArgumentException { return xmlSW.getProperty(name); } } 

Using this result leads to the desired result. Now, to file a bug report ...