abstract class Identity implements TransformAction<TransformParameters.None> {
    @InputArtifact
    abstract Provider<FileSystemLocation> getInputArtifact()

    void transform(TransformOutputs outputs) {
        outputs.file(inputArtifact)
    }
}

abstract class IllegalTransform implements TransformAction<TransformParameters.None> {
    void transform(TransformOutputs outputs) {

The implementation of the artifact transform action is a class implementing link:{groovyDslPath}/org.gradle.api.artifacts.transform.TransformAction.html[TransformAction].
You need to implement the `transform()` method on the action, which converts an input artifact into zero, one or multiple of output artifacts.

            apply plugin:'java-library'
        """

        buildFile << """
            import org.gradle.api.artifacts.transform.TransformParameters
            import org.gradle.api.artifacts.transform.TransformAction

            plugins {
                id 'java'
                id 'application'
            }

            def artifactType = Attribute.of('artifactType', String)

import com.google.gson.Gson;
import org.gradle.api.Task;
import org.gradle.api.UncheckedIOException;
import org.gradle.api.artifacts.transform.CacheableTransform;
import org.gradle.api.artifacts.transform.TransformAction;
import org.gradle.api.file.ConfigurableFileCollection;
import org.gradle.api.file.EmptyFileVisitor;
import org.gradle.api.file.FileVisitDetails;
import org.gradle.api.file.RegularFileProperty;

            def usage = Attribute.of('usage', String)
            def artifactType = Attribute.of('artifactType', String)

            abstract class FileSizer implements TransformAction<Parameters> {
                interface Parameters extends TransformParameters {
                    @Input
                    String getSuffix()
                    void setSuffix(String suffix)
                }

        """
        buildFile << """
            ${showTransformedFilesTask}
            ${unzipTransform}

            @CacheableTransform
            abstract class AugmentTransform implements TransformAction<Parameters> {
                interface Parameters extends TransformParameters {
                    @InputFiles
                    @PathSensitive(PathSensitivity.RELATIVE)

     *         inputFiles.from("my-input-file")
     *     }
     * }
     * </pre>
     *
     * @see TransformAction
     * @since 5.3
     */
    <T extends TransformParameters> void registerTransform(Class<? extends TransformAction<T>> actionType, Action<? super TransformSpec<T>> registrationAction);

    /**

        """
        buildFile << """
            ${showTransformedFilesTask}
            ${unzipTransform}

            @CacheableTransform
            abstract class AugmentTransform implements TransformAction<Parameters> {
                interface Parameters extends TransformParameters {
                    @InputFiles
                    @PathSensitive(PathSensitivity.RELATIVE)

import org.gradle.api.Action
import org.gradle.api.artifacts.FileCollectionDependency
import org.gradle.api.artifacts.component.ComponentIdentifier
import org.gradle.api.artifacts.transform.TransformAction
import org.gradle.api.artifacts.transform.TransformParameters
import org.gradle.api.artifacts.type.ArtifactTypeDefinition.ARTIFACT_TYPE_ATTRIBUTE
import org.gradle.api.attributes.Attribute

import org.gradle.api.artifacts.dsl.ExternalModuleDependencyVariantSpec;
import org.gradle.api.artifacts.query.ArtifactResolutionQuery;
import org.gradle.api.artifacts.transform.TransformAction;
import org.gradle.api.artifacts.transform.TransformParameters;
import org.gradle.api.artifacts.transform.TransformSpec;
import org.gradle.api.artifacts.type.ArtifactTypeContainer;