*
     * @param classRealm The class realm hosting the build extensions of this project, may be {@code null}.
     */
    public void setClassRealm(ClassRealm classRealm) {
        this.classRealm = classRealm;
    }

    /**
     * Gets the project's class realm. This class realm hosts the build extensions of the project.

  </parent>

  <artifactId>maven-api</artifactId>
  <packaging>pom</packaging>
  <name>Maven 4 API</name>
  <description>A new immutable API for Maven 4 to better manage what plugins and extensions can influence.</description>

  <modules>
    <module>maven-api-meta</module>
    <module>maven-api-di</module>
    <module>maven-api-xml</module>
    <module>maven-api-model</module>

Use this directory to add third party extensions to Maven Core. These extensions can either extend or override

     * <p>
     * This type registry is NOT used by Maven Core: Maven replaces it during Session creation with a type registry
     * that supports extending it (i.e. via Maven Extensions).
     * <p>
     * Important: this "static" list of types should be in-sync with core provided types.
     */
    protected ArtifactTypeRegistry getArtifactTypeRegistry() {

package org.apache.maven.api.spi;

import org.apache.maven.api.annotations.Consumer;
import org.apache.maven.api.annotations.Experimental;

/**
 * Marker interface to indicate services that can be provided by plugins and extensions.
 */
@Experimental
@Consumer

            // extensionArtifacts
            Set<Artifact> extensionArtifacts = new HashSet<>();
            List<Extension> extensions =
                    project.getModel().getDelegate().getBuild().getExtensions();
            if (extensions != null) {
                for (Extension ext : extensions) {
                    String version;
                    if (ext.getVersion() == null || ext.getVersion().isEmpty()) {

 */
public interface ModelBuildingListener {

    /**
     * Notifies the listener that the model has been constructed to the extent where build extensions can be processed.
     *
     * @param event The details about the event.
     */
    default void buildExtensionsAssembled(ModelBuildingEvent event) {}

package org.apache.maven.api;

import org.apache.maven.api.annotations.Experimental;
import org.apache.maven.api.annotations.Nonnull;

/**
 * Interface that defines some kind of enums that can be extended by Maven plugins or extensions.
 *
 * Implementation must have {@code equals()} and {@code hashCode()} implemented, so implementations of this interface
 * can be used as keys.
 *
 * @since 4.0.0
 */
@Experimental

        return plugins.keySet();
    }

    /**
     * Performs a lookup using Plexus API to make sure we can look up only "visible" (see Maven classloading) components
     * from current module and for example not extensions coming from other modules.
     */
    private LifecycleMapping lookupLifecycleMapping(final String packaging) {
        return lookup.lookupOptional(LifecycleMapping.class, packaging).orElse(null);
    }

 * {{{./artifact-handlers.html}default artifact handlers}}, to manage {{{../maven-model/maven.html#class_dependency}dependency types}},

 * {{{./extension.html}extension descriptor}} and {{{./core-extensions.html}core extensions}},

 * {{{/guides/mini/guide-maven-classloading.html}classloader hierarchy}} done by <<<ClassRealmManager>>> component