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DataKernel has an extremely lightweight DI with ground-breaking design principles. It supports nested scopes, singletons, object factories, modules and plugins which allow to transform graph of dependencies at startup time without any reflection.

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package io.datakernel.di.core;

import io.datakernel.di.annotation.ScopeAnnotation;
import io.datakernel.di.util.AbstractAnnotation;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import java.lang.annotation.Annotation;

import static io.datakernel.di.util.Utils.checkArgument;

/**
 * Scopes work with annotations in just the same way {@link Name Names} work with them.
 *
 * @see Name
 */
public final class Scope extends AbstractAnnotation {
	public static final Scope[] UNSCOPED = new Scope[0];
	private final boolean threadsafe;

	protected Scope(@NotNull Class annotationType, @Nullable Annotation annotation, boolean threadsafe) {
		super(annotationType, annotation);
		this.threadsafe = threadsafe;
	}

	/**
	 * Creates a Scope from a marker (or stateless) annotation, only identified by its class.
	 */
	public static Scope of(Class annotationType) {
		checkArgument(isMarker(annotationType), "Scope by annotation type only accepts marker annotations with no arguments");
		ScopeAnnotation scopeAnnotation = annotationType.getAnnotation(ScopeAnnotation.class);
		checkArgument(scopeAnnotation != null, "Only annotations annotated with @ScopeAnnotation meta-annotation are allowed");
		return new Scope(annotationType, null, scopeAnnotation.threadsafe());
	}

	/**
	 * Creates a Scope from a real (or its custom surrogate impl) annotation instance.
	 */
	public static Scope of(Annotation annotation) {
		Class annotationType = annotation.annotationType();
		ScopeAnnotation scopeAnnotation = annotationType.getAnnotation(ScopeAnnotation.class);
		checkArgument(scopeAnnotation != null, "Only annotations annotated with @ScopeAnnotation meta-annotation are allowed");
		return isMarker(annotationType) ?
				new Scope(annotationType, null, scopeAnnotation.threadsafe()) :
				new Scope(annotationType, annotation, scopeAnnotation.threadsafe());
	}

	public boolean isThreadsafe() {
		return threadsafe;
	}
}