apache/maven · error · IllegalArgumentException

{} cannot be null

Error message

{} cannot be null

What it means

Generic null guard used by DefaultSettingsXmlFactory for its request and content parameters; the message interpolates the parameter name, so it surfaces as 'request cannot be null' or 'content cannot be null'. read() rejects a null request; write() rejects a null request and a request whose getContent() is null.

Source

Thrown at impl/maven-impl/src/main/java/org/apache/maven/impl/DefaultSettingsXmlFactory.java:106

            if (formatter != null) {
                xmlWriter.setAddLocationInformation(true);
                Function<InputLocation, String> adapter = formatter::apply;
                xmlWriter.setStringFormatter(adapter);
            }

            if (writer != null) {
                xmlWriter.write(writer, content);
            } else {
                xmlWriter.write(outputStream, content);
            }
        } catch (Exception e) {
            throw new XmlWriterException("Unable to write settings: " + getMessage(e), getLocation(e), e);
        }
    }

    static <T> T nonNull(T t, String name) {
        if (t == null) {
            throw new IllegalArgumentException(name + " cannot be null");
        }
        return t;
    }
}

View on GitHub (pinned to e4093d4e12)

Solutions

1. Always set .content(settings) on write requests
2. Null-check the request object before the call
3. Add your own requireNonNull checks earlier so failures carry your call-site context

Example fix

// before
settingsXmlFactory.write(XmlWriterRequest.builder()
    .writer(sw)
    .build()); // throws: content cannot be null

// after
settingsXmlFactory.write(XmlWriterRequest.builder()
    .content(settings)
    .writer(sw)
    .build());

Objects.requireNonNull(request, "request");
if (writing && request.getContent() == null) {
    throw new IllegalStateException("settings write requires non-null content");
}
// now safe to call the factory

When it happens

Trigger: Passing a null XmlReaderRequest/XmlWriterRequest to read/write; calling write with a request built without .content(settings).

Common situations: Optional-based call chains that hand null through; builder refactors that drop the content line; helper methods that accept nullable requests.

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

• reader or inputStream must be non null
• writer or outputStream must be non null
• Illegal request type: " + requestType
• Illegal event type: " + eventType
• Repository identifier missing

AI-assisted analysis of apache/maven@e4093d4e12 (2026-08-21). Data as JSON: /api/errors/804eb323bae56e8f. Report an issue: GitHub.