apache/maven · error · IllegalArgumentException

reader or inputStream must be non null

Error message

reader or inputStream must be non null

What it means

DefaultSettingsXmlFactory.read accepts only a Reader or an InputStream - unlike the model and plugin factories it does not consult path or url on the request. If both reader and inputStream are null it throws IllegalArgumentException before parsing.

Solutions

1. Open the source yourself and pass .inputStream(Files.newInputStream(path)) or .reader(Files.newBufferedReader(path))
2. For URLs, use .inputStream(url.openStream()) and close it afterwards
3. Check getReader()/getInputStream() for null before calling read

Example fix

// before
Settings s = settingsXmlFactory.read(XmlReaderRequest.builder()
    .path(settingsPath) // ignored: this factory wants reader or inputStream
    .build()); // throws

// after
try (InputStream is = Files.newInputStream(settingsPath)) {
    Settings s = settingsXmlFactory.read(XmlReaderRequest.builder()
        .inputStream(is)
        .build());
}

XmlReaderRequest req = XmlReaderRequest.builder().build();
if (req.getReader() == null && req.getInputStream() == null) {
    try (InputStream is = Files.newInputStream(settingsPath)) {
        settingsXmlFactory.read(XmlReaderRequest.builder()
            .inputStream(is)
            .build());
    }
} else {
    settingsXmlFactory.read(req);
}

When it happens

Trigger: Building a XmlReaderRequest for settings with only .path(...) or .url(...) set; those fields are ignored by this factory, so the call is rejected. Also a request with no source at all.

Common situations: Reusing request-builder code from DefaultModelXmlFactory or DefaultPluginXmlFactory, which do support path/url; developers assuming a symmetric API across all Maven XML factories.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• path, url, reader or inputStream must be non null
• reader or inputStream must be non null
• writer or outputStream must be non null
• cannot be null
• Unable to read settings:

AI-assisted analysis of apache/maven@e4093d4e12 (2026-08-21). Data as JSON: /api/errors/6c2326ec6eb2416a. Report an issue: GitHub.

Appendix: source

Thrown at impl/maven-impl/src/main/java/org/apache/maven/impl/DefaultSettingsXmlFactory.java:53

import org.apache.maven.api.settings.InputLocation;
import org.apache.maven.api.settings.InputSource;
import org.apache.maven.api.settings.Settings;
import org.apache.maven.settings.v4.SettingsStaxReader;
import org.apache.maven.settings.v4.SettingsStaxWriter;

import static org.apache.maven.impl.StaxLocation.getLocation;
import static org.apache.maven.impl.StaxLocation.getMessage;

@Named
@Singleton
public class DefaultSettingsXmlFactory implements SettingsXmlFactory {
    @Override
    public Settings read(@Nonnull XmlReaderRequest request) throws XmlReaderException {
        nonNull(request, "request");
        Reader reader = request.getReader();
        InputStream inputStream = request.getInputStream();
        if (reader == null && inputStream == null) {
            throw new IllegalArgumentException("reader or inputStream must be non null");
        }
        try {
            InputSource source = null;
            if (request.getModelId() != null || request.getLocation() != null) {
                source = InputSource.of(request.getLocation());
            }
            SettingsStaxReader xml = request.getTransformer() != null
                    ? new SettingsStaxReader(request.getTransformer()::transform)
                    : new SettingsStaxReader();
            xml.setAddDefaultEntities(request.isAddDefaultEntities());
            if (reader != null) {
                return xml.read(reader, request.isStrict(), source);
            } else {
                return xml.read(inputStream, request.isStrict(), source);
            }
        } catch (Exception e) {
            throw new XmlReaderException("Unable to read settings: " + getMessage(e), getLocation(e), e);
        }

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