ADDITIONAL SYSTEM INFORMATION :
> java -version
java version "21.0.2" 2024-01-16 LTS
Java(TM) SE Runtime Environment (build 21.0.2+13-LTS-58)
Java HotSpot(TM) 64-Bit Server VM (build 21.0.2+13-LTS-58, mixed mode, sharing)


A DESCRIPTION OF THE PROBLEM :
After transforming an XML source to a StAXResult, the produced StartDocument event location is null which further causes NPE in at least one scenario. The XMLEvent.getLocation() API doesn't suggest it could be null, so it should never be:

* https://docs.oracle.com/en/java/javase/21/docs/api/java.xml/javax/xml/stream/events/XMLEvent.html#getLocation()


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Run the provided test case: `java TransformPipelineTest.java`


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
No failure:

```
Event buffer:
StartDocumentEvent(location: <non-null>)
...

<hello>World</hello>
```

ACTUAL -
Failing:

```
Event buffer:
StartDocumentEvent(location: null)
StartElementEvent(location: DummyLocation)
CharacterEvent(location: DummyLocation)
EndElementEvent(location: DummyLocation)
EndDocumentEvent(location: DummyLocation)

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "javax.xml.stream.Location.getSystemId()" because the return value of "javax.xml.stream.events.XMLEvent.getLocation()" is null
at java.xml/javax.xml.transform.stax.StAXSource.<init>(StAXSource.java:122)
at TransformPipelineTest.main(TransformPipelineTest.java:52)
```


---------- BEGIN SOURCE ----------
//package ;

import java.io.StringReader;
import java.util.ArrayDeque;
import java.util.Iterator;
import java.util.Optional;
import java.util.Queue;

import javax.xml.XMLConstants;
import javax.xml.namespace.NamespaceContext;
import javax.xml.stream.Location;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLEventWriter;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.XMLEvent;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.stax.StAXResult;
import javax.xml.transform.stax.StAXSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;

public class TransformPipelineTest {

    public static void main(String[] args) throws Exception {
        Source source = new StreamSource(new StringReader("<hello>World</hello>"));

        Transformer transformation1 = sampleTransformation();
        //Transformer transformation1 = defaultIdentity();
        XMLEventBufferWriter bufferWriter = new XMLEventBufferWriter();
        Result intermediate = new StAXResult(bufferWriter);
        transformation1.transform(source, intermediate);

        System.out.println("Event buffer:");
        for (XMLEvent event : bufferWriter.getBuffer()) {
            Location location = event.getLocation();
            System.out.printf("\t%s(location: %s)%n",
                    event.getClass().getSimpleName(),
                    (location == null) ? "null" :
                            location.getClass().getSimpleName());
        }
        System.out.println();

        //Transformer transformation2 = sampleTransformation();
        Transformer transformation2 = defaultIdentity();
        XMLEventBufferReader bufferReader = new XMLEventBufferReader(bufferWriter.getBuffer());
        transformation2.transform(new StAXSource(bufferReader),
        //transformation2.transform(new NullLocationStAXSource(bufferReader),
                                  new StreamResult(System.out));
    }

    // An identity transform, really
    private static final String SAMPLE_XSLT = "<xsl:stylesheet "
              + "version='1.0' xmlns:xsl='http://www.w3.org/1999/XSL/Transform&#39;>"
            + "<xsl:template match='@*|node()'>"
              + "<xsl:copy>"
                + "<xsl:apply-templates select='@*|node()' />"
              + "</xsl:copy>"
            + "</xsl:template>"
          + "</xsl:stylesheet>";

    static Transformer sampleTransformation()
            throws TransformerConfigurationException {
        return transformation(Optional
                .of(new StreamSource(new StringReader(SAMPLE_XSLT))));
    }

    static Transformer defaultIdentity()
            throws TransformerConfigurationException {
        return transformation(Optional.empty());
    }

    private static Transformer transformation(Optional<Source> xslt)
            throws TransformerConfigurationException {
        TransformerFactory tf = TransformerFactory.newInstance();
        tf.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, true);

        Transformer transformer = xslt.isPresent()
                                  ? tf.newTransformer(xslt.get())
                                  : tf.newTransformer();
        transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
        return transformer;
    }

} // class TransformPipelineTest


class XMLEventBufferReader implements XMLEventReader {

    private Iterator<XMLEvent> events;
    private XMLEvent nextEvent;

    public XMLEventBufferReader(Iterable<XMLEvent> source) {
        this.events = source.iterator();
    }

    @Override
    public Object getProperty(String name) throws IllegalArgumentException {
        throw notImplementedException();
    }

    @Override
    public boolean hasNext() {
        return events.hasNext();
    }

    @Override
    public Object next() {
        return nextEvent();
    }

    @Override
    public XMLEvent nextEvent() {
        XMLEvent next = nextEvent;
        if (next == null) {
            next = events.next();
        } else {
            nextEvent = null;
        }
        return next;
    }

    @Override
    public XMLEvent peek() {
        XMLEvent next = nextEvent;
        if (next == null) {
            if (!hasNext()) return null;

            next = nextEvent();
            nextEvent = next;
        }
        return next;
    }

    @Override
    public XMLEvent nextTag() throws XMLStreamException {
        throw notImplementedException();
    }

    @Override
    public String getElementText() throws XMLStreamException {
        throw notImplementedException();
    }

    private static IllegalStateException notImplementedException() {
        return new IllegalStateException("Not implemented");
    }

    @Override
    public void close() {
        // no-op
    }

} // class XMLEventBufferReader


class XMLEventBufferWriter implements XMLEventWriter {

    private final Queue<XMLEvent> buffer;

    public XMLEventBufferWriter() {
        buffer = new ArrayDeque<>();
    }

    public Iterable<XMLEvent> getBuffer() {
        return buffer;
    }

    @Override
    public void add(XMLEvent event) {
        buffer.add(event);
    }

    @Override
    public void add(XMLEventReader reader) {
        throw notImplementedException();
    }

    @Override
    public String getPrefix(String uri) {
        throw notImplementedException();
    }

    @Override
    public void setPrefix(String prefix, String uri) {
        throw notImplementedException();
    }

    @Override
    public void setDefaultNamespace(String uri) {
        throw notImplementedException();
    }

    @Override
    public void setNamespaceContext(NamespaceContext context) {
        throw notImplementedException();
    }

    @Override
    public NamespaceContext getNamespaceContext() {
        throw notImplementedException();
    }

    private static IllegalStateException notImplementedException() {
        return new IllegalStateException("Not implemented");
    }

    @Override
    public void flush() {
        // no-op
    }

    @Override
    public void close() {
        // no-op
    }

} // class XMLEventBufferWriter


class NullLocationStAXSource extends StAXSource {

    private final XMLEventReader xmlEventReader;

    public NullLocationStAXSource(XMLEventReader xmlEventReader)
            throws XMLStreamException {
        this("tag:example.net,2024-03:dummy", xmlEventReader);
    }

    public NullLocationStAXSource(String systemId, XMLEventReader xmlEventReader)
            throws XMLStreamException {
        super(dummyReader(systemId));
        this.xmlEventReader = xmlEventReader;
    }

    @Override
    public XMLEventReader getXMLEventReader() {
        return xmlEventReader;
    }

    private static XMLEventReader dummyReader(String systemId)
            throws XMLStreamException {
        XMLInputFactory xif = XMLInputFactory.newInstance();
        return xif.createXMLEventReader(systemId, new StringReader("<dummy />"));
    }

} // class NullLocationStAXSource

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
More of a hack than an actual solution – see the NullLocationStAXSource class in the provided test case. It doesn't work with the Woodstox StAX provider plugged into the runtime:

```
Event buffer:
        StartDocumentEventImpl(location: null)
        SimpleStartElement(location: null)
        CharactersEventImpl(location: null)
        EndElementEventImpl(location: null)
        EndDocumentEventImpl(location: null)

Exception in thread "main" javax.xml.transform.TransformerException: javax.xml.transform.TransformerException: java.lang.NullPointerException: Cannot invoke "javax.xml.stream.Location.getSystemId()" because the return value of "javax.xml.stream.events.XMLEvent.getLocation()" is null
...
java.lang.NullPointerException: Cannot invoke "javax.xml.stream.Location.getSystemId()" because the return value of "javax.xml.stream.events.XMLEvent.getLocation()" is null
at java.xml/com.sun.org.apache.xalan.internal.xsltc.trax.StAXEvent2SAX$1.getSystemId(StAXEvent2SAX.java:286)
at java.xml/com.sun.org.apache.xml.internal.dtm.ref.sax2dtm.SAX2DTM.setDocumentLocator(SAX2DTM.java:1610)
at java.xml/com.sun.org.apache.xalan.internal.xsltc.trax.StAXEvent2SAX.handleStartDocument(StAXEvent2SAX.java:275)
at java.xml/com.sun.org.apache.xalan.internal.xsltc.trax.StAXEvent2SAX.bridge(StAXEvent2SAX.java:160)
at java.xml/com.sun.org.apache.xalan.internal.xsltc.trax.StAXEvent2SAX.parse(StAXEvent2SAX.java:114)
at java.xml/com.sun.org.apache.xalan.internal.xsltc.dom.XSLTCDTMManager.getDTM(XSLTCDTMManager.java:294)
at java.xml/com.sun.org.apache.xalan.internal.xsltc.dom.XSLTCDTMManager.getDTM(XSLTCDTMManager.java:214)
at java.xml/com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.getDOM(TransformerImpl.java:582)
at java.xml/com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:783)
at java.xml/com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:395)
at TransformPipelineTest.main(TransformPipelineTest.java:53)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
at java.base/java.lang.reflect.Method.invoke(Method.java:580)
at jdk.compiler/com.sun.tools.javac.launcher.Main.execute(Main.java:484)
at jdk.compiler/com.sun.tools.javac.launcher.Main.run(Main.java:208)
at jdk.compiler/com.sun.tools.javac.launcher.Main.main(Main.java:135)
```


FREQUENCY : always