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Experimental extension to make it easier to compile applications into a GraalVM native image
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/*
 * SPDX-License-Identifier: Apache-2.0
 * Copyright Red Hat Inc. and Hibernate Authors
 */
package org.hibernate.graalvm.internal;

import java.lang.reflect.Constructor;
import java.lang.reflect.Executable;
import java.util.ArrayList;

import org.graalvm.nativeimage.hosted.RuntimeClassInitialization;
import org.hibernate.internal.util.ReflectHelper;

import org.graalvm.nativeimage.hosted.Feature;
import org.graalvm.nativeimage.hosted.RuntimeReflection;

/**
 * This is a best effort, untested experimental GraalVM feature to help people getting Hibernate ORM
 * to work with GraalVM native images.
 * There are multiple reasons for this to be untested. One is that for tests to be effective they would
 * need very extensive coverage of all functionality: the point of this class being a list of all things
 * being initialized reflectively, it's not possible to ensure that the list is comprehensive without the
 * tests being comprehensive as well.
 * The other problem is that this is listing just that "static needs" of Hibernate ORM: it will very likely
 * also need to access reflectively the user's domain model and the various extension points, depending on
 * configurations. Such configuration - and especially the domain model - is dynamic by its very own nature,
 * and therefore this list is merely provided as a useful starting point, but it needs to be extended;
 * such extensions could be automated, or will need to be explicitly passed to the native-image arguments.
 * 
 *     In conclusion, it's not possible to provide a fully comprehensive list: take this as a hopefully
 *     useful building block.
 * 
 * @author Sanne Grinovero
 */
public class GraalVMStaticFeature implements Feature {

	public void beforeAnalysis(Feature.BeforeAnalysisAccess before) {
		final Class[] needsHavingSimpleConstructors = StaticClassLists.typesNeedingDefaultConstructorAccessible();
		final Class[] needingAllConstructorsAccessible = StaticClassLists.typesNeedingAllConstructorsAccessible();
		final Class[] typesNeedingRuntimeInitialization = StaticClassLists.typesNeedingRuntimeInitialization();
		//Size formula is just a reasonable guess:
		ArrayList executables = new ArrayList<>( needsHavingSimpleConstructors.length + needingAllConstructorsAccessible.length * 3 );
		for ( Class c : needsHavingSimpleConstructors ) {
			executables.add( ReflectHelper.getDefaultConstructor( c ) );
		}
		for ( Class c : needingAllConstructorsAccessible) {
			for ( Constructor declaredConstructor : c.getDeclaredConstructors() ) {
				executables.add( declaredConstructor );
			}
		}
		RuntimeReflection.register( needsHavingSimpleConstructors );
		RuntimeReflection.register( needingAllConstructorsAccessible );
		RuntimeReflection.register( StaticClassLists.typesNeedingArrayCopy() );
		RuntimeReflection.register( executables.toArray(new Executable[0]) );

		RuntimeClassInitialization.initializeAtRunTime( typesNeedingRuntimeInitialization );
	}

	@Override
	public String getDescription() {
		return "Hibernate ORM's static reflection registrations for GraalVM";
	}
}