apache/maven · warning · InvalidVersionSpecificationException

Only fully-qualified sets allowed in multiple set scenario:

Error message

Only fully-qualified sets allowed in multiple set scenario: {}

What it means

Building the effective toolchains (user plus installation/project toolchains.xml) produced Problem entries. Maven prints this header followed by one 'message @ location' line per problem, then continues with whatever toolchains could be merged. A misdeclared toolchain can later fail to match a <toolchain> requirement in a plugin, silently falling back to default JDK/tool selection.

Source

Thrown at compat/maven-artifact/src/main/java/org/apache/maven/artifact/versioning/VersionRange.java:148

            if (upperBound != null) {
                if (restriction.getLowerBound() == null
                        || restriction.getLowerBound().compareTo(upperBound) < 0) {
                    throw new InvalidVersionSpecificationException("Ranges overlap: " + spec);
                }
            }
            restrictions.add(restriction);
            upperBound = restriction.getUpperBound();

            process = process.substring(index + 1).trim();

            if (process.startsWith(",")) {
                process = process.substring(1).trim();
            }
        }

        if (!process.isEmpty()) {
            if (!restrictions.isEmpty()) {
                throw new InvalidVersionSpecificationException(
                        "Only fully-qualified sets allowed in multiple set scenario: " + spec);
            } else {
                version = new DefaultArtifactVersion(process);
                restrictions.add(Restriction.EVERYTHING);
            }
        }

        cached = new VersionRange(version, restrictions);
        CACHE_SPEC.put(spec, cached);
        return cached;
    }

    private static Restriction parseRestriction(String spec) throws InvalidVersionSpecificationException {
        boolean lowerBoundInclusive = spec.startsWith("[");
        boolean upperBoundInclusive = spec.endsWith("]");

        String process = spec.substring(1, spec.length() - 1).trim();

View on GitHub (pinned to e4093d4e12)

Solutions

1. Read each following 'message @ location' line to find the exact file and position
2. Fix the reported entry in the toolchains.xml (usually ~/.m2/toolchains.xml or .mvn/toolchains.xml)
3. Validate shape: xmllint --noout on the file; ensure each <toolchain> has <type> and the type-specific fields
4. Re-run mvn and confirm the warning block disappears before relying on toolchain selection

Example fix

<!-- before -->
<toolchains>
  <toolchain>
    <type>jdk</type>
    <provides><version>17</version></provides>
  </toolchain>
</toolchains>
<!-- after: required jdkHome present -->
<toolchains>
  <toolchain>
    <type>jdk</type>
    <provides><version>17</version></provides>
    <configuration><jdkHome>/usr/lib/jvm/java-17</jdkHome></configuration>
  </toolchain>
</toolchains>

xmllint --noout ~/.m2/toolchains.xml 2>/dev/null
xmllint --noout .mvn/toolchains.xml 2>/dev/null
echo 'toolchains XML validated'

When it happens

Trigger: A toolchains.xml that is malformed, uses unknown elements, or declares a toolchain missing required fields (for example a jdk toolchain without a jdkHome).

Common situations: Hand-edited ~/.m2/toolchains.xml after JDK updates; CI provisioning toolchains files via templates with unfilled placeholders; conflicting user and project toolchains files.

Related errors

• Single version must be surrounded by []: {}
• The artifact has no valid ranges
• Cannot read toolchains file at " + userToolchainsFile.getAbs
• Provides token '" + key + "' doesn't have any value configur
• Java toolchain without the jdkHome configuration element.

AI-assisted analysis of apache/maven@e4093d4e12 (2026-08-21). Data as JSON: /api/errors/d0993a15a5b32cdc. Report an issue: GitHub.