package sample;

import org.hibernate.boot.MetadataSources;
import org.hibernate.cfg.Configuration;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.context.event.ApplicationReadyEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.data.jpa.repository.support.JpaRepositoryFactory;
import org.springframework.data.repository.Repository;
import org.springframework.stereotype.Component;

import java.util.Optional;
import javax.persistence.*;

@ComponentScan
public class Main {
    public static void main(String[] args) {
        SpringApplication.run(Main.class, args);
    }
}

@Entity
class Widget {
    @Id
    private Integer id;
}

interface WidgetRepository extends Repository<Widget, Integer> {
    Optional<Widget> findById(Integer id);
}

@Component
class Sample implements ApplicationListener<ApplicationReadyEvent> {
    @Override
    public void onApplicationEvent(ApplicationReadyEvent applicationReadyEvent) {
        MetadataSources metadataSources = new MetadataSources()
                .addAnnotatedClass(Widget.class);

        Configuration configuration = new Configuration(metadataSources)
                .setProperty("hibernate.connection.url", "jdbc:postgresql://localhost/database");

        EntityManagerFactory entityManagerFactory = configuration.buildSessionFactory();
        EntityManager entityManager = entityManagerFactory.createEntityManager();
        JpaRepositoryFactory repositoryFactory = new JpaRepositoryFactory(entityManager);

        // prints class sample.Widget
        entityManager.getMetamodel().getManagedTypes().forEach(ty -> System.err.println(ty.getJavaType()));

        // throws java.lang.IllegalArgumentException: Not a managed type: class sample.Widget
        entityManager.getMetamodel().managedType(Widget.class);

        // throws java.lang.IllegalArgumentException: Not a managed type: class sample.Widget
        WidgetRepository widgetRepository = repositoryFactory.getRepository(WidgetRepository.class);
    }
}