quarkusio/quarkus · error · MojoExecutionException

Either the `extension` or `extensions` parameter must be set

Error message

Either the `extension` or `extensions` parameter must be set

What it means

AddExtensionMojo.validateParameters enforces that exactly one of the mutually exclusive parameters `extension` (single) or `extensions` (list) is provided. Throwing when neither is set or when both are set, since the mojo cannot unambiguously decide which extensions to add.

Source

Thrown at devtools/maven/src/main/java/io/quarkus/maven/AddExtensionMojo.java:44

public class AddExtensionMojo extends QuarkusProjectMojoBase {

    /**
     * The list of extensions to be added.
     */
    @Parameter(property = "extensions")
    Set<String> extensions;

    /**
     * For usability reason, this parameter allows adding a single extension.
     */
    @Parameter(property = "extension")
    String extension;

    @Override
    protected void validateParameters() throws MojoExecutionException {
        if ((StringUtils.isBlank(extension) && (extensions == null || extensions.isEmpty())) // None are set
                || (!StringUtils.isBlank(extension) && extensions != null && !extensions.isEmpty())) { // Both are set
            throw new MojoExecutionException("Either the `extension` or `extensions` parameter must be set");
        }
    }

    @Override
    public void doExecute(final QuarkusProject quarkusProject, final MessageWriter log)
            throws MojoExecutionException {
        Set<String> ext = new HashSet<>();
        if (extensions != null && !extensions.isEmpty()) {
            ext.addAll(extensions);
        } else {
            // Parse the "extension" just in case it contains several comma-separated values
            // https://github.com/quarkusio/quarkus/issues/2393
            ext.addAll(Arrays.stream(extension.split(",")).map(String::trim).collect(toSet()));
        }

        try {
            AddExtensions addExtensions = new AddExtensions(quarkusProject)
                    .extensions(ext.stream().map(String::trim).collect(toSet()));

View on GitHub (pinned to e1c734241f)

Solutions

1. Pass exactly one: `mvn quarkus:add-extension -Dextensions=hibernate-orm,rest` or `-Dextension=hibernate-orm`.
2. Remove the duplicate parameter if both were supplied.
3. In pom.xml configuration, configure either <extensions> or <extension>, not both.

Example fix

// before
mvn quarkus:add-extension -Dextension=agenda -Dextensions=hibernate-orm
// after
mvn quarkus:add-extension -Dextensions=agenda,hibernate-orm

if (project.hasProperty('extension') && project.hasProperty('extensions')) throw new IllegalArgumentException('Use only -Dextension or -Dextensions, not both')

try { ... } catch (MojoExecutionException e) { getLog().error('Pass exactly one of -Dextension or -Dextensions: ' + e.getMessage()); }

When it happens

Trigger: Running `mvn quarkus:add-extension` with no -Dextension/-Dextensions parameters, or supplying both -Dextension=x and -Dextensions=a,b at the same time.

Common situations: Forgetting to pass -Dextensions on the command line; CI scripts passing both forms after copy-paste; empty `extensions` property combining with a blank `extension`.

Related errors

• This goal requires a Quarkus extension registry client to be
• Unsupported format: ${format}
• Cannot specify both class and method name
• The project artifact's extension is '${extension}' while thi
• Specifying a stream requires the Quarkus extension registry

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/31d6fec587b98cfd. Report an issue: GitHub.