Where did Configuration.generateSchemaCreationScript() go in Hibernate 5

The new bootstrap API allows for many customizations, but assuming you don't need those, the shortest invocation would look like that, applying default values for service registries and all the settings:

Metadata metadata = new MetadataSources()
    .addAnnotatedClass( MyEntity.class )
    .build();

new SchemaExport( (MetadataImplementor) metadata )
    .setOutputFile( "my-statements.ddl" )
    .create( Target.NONE );

Update: Providing example for applying configuration propperties

There are several ways to inject properties for connection URL, dialect etc. E.g. you could provide a file hibernate.properties or you use a service registry customized with the required settings:

StandardServiceRegistry registry = new StandardServiceRegistryBuilder()
    .applySetting( "hibernate.connection.url", "jdbc:h2:mem:db1;DB_CLOSE_DELAY=-1" )
    .build();

Metadata metadata = new MetadataSources( registry )
    .build();

One example of the new SchemaExport initialization is found in SchemaExportTask:

final BootstrapServiceRegistry bsr = new BootstrapServiceRegistryBuilder().build();

final MetadataSources metadataSources = new MetadataSources( bsr );
final StandardServiceRegistryBuilder ssrBuilder = new StandardServiceRegistryBuilder( bsr );

if ( configurationFile != null ) {
    ssrBuilder.configure( configurationFile );
}
if ( propertiesFile != null ) {
    ssrBuilder.loadProperties( propertiesFile );
}
ssrBuilder.applySettings( getProject().getProperties() );

for ( String fileName : getFiles() ) {
    if ( fileName.endsWith(".jar") ) {
        metadataSources.addJar( new File( fileName ) );
    }
    else {
        metadataSources.addFile( fileName );
    }
}


final StandardServiceRegistryImpl ssr = (StandardServiceRegistryImpl) ssrBuilder.build();
final MetadataBuilder metadataBuilder = metadataSources.getMetadataBuilder( ssr );

ClassLoaderService classLoaderService = bsr.getService( ClassLoaderService.class );
if ( implicitNamingStrategy != null ) {
    metadataBuilder.applyImplicitNamingStrategy(
            (ImplicitNamingStrategy) classLoaderService.classForName( implicitNamingStrategy ).newInstance()
    );
}
if ( physicalNamingStrategy != null ) {
    metadataBuilder.applyPhysicalNamingStrategy(
            (PhysicalNamingStrategy) classLoaderService.classForName( physicalNamingStrategy ).newInstance()
    );
}

return new SchemaExport( (MetadataImplementor) metadataBuilder.build() )
    .setHaltOnError( haltOnError )
    .setOutputFile( outputFile.getPath() )
    .setDelimiter( delimiter );

Of course, you can customize it according to your needs.

I exported it this way with hibernate 5.4.9.Final:

import org.hibernate.boot.Metadata;
import org.hibernate.boot.MetadataSources;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.tool.hbm2ddl.SchemaExport;
import org.hibernate.tool.schema.TargetType;

import java.util.EnumSet;

public class ExportSchema {
    public static void main(String[] args) {
        final StandardServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder()
                .applySetting("hibernate.dialect", "org.hibernate.dialect.H2Dialect")
                .build();
        final Metadata metadata = new MetadataSources(serviceRegistry)
                .addAnnotatedClass(...)
                .buildMetadata();
        new SchemaExport()
                .setFormat(true)
                .setDelimiter(";")
                .setOutputFile("schema.sql")
                .execute(EnumSet.of(TargetType.SCRIPT), SchemaExport.Action.CREATE, metadata);
    }
}

Thanks to the answers by Vlad and Gunnar, I've managed to find my way through the new configuration API to produce the equivalent export logic with the following. Of course, history shows that this API will break again, so make sure to choose the appropriate version:

Hibernate 5.2:

MetadataSources metadata = new MetadataSources(
    new StandardServiceRegistryBuilder()
        .applySetting("hibernate.dialect", "org.hibernate.dialect.H2Dialect")
        .applySetting("javax.persistence.schema-generation-connection", connection)
        .build());

// [...] adding annotated classes to metadata here...
metadata.addAnnotatedClass(...);

SchemaExport export = new SchemaExport();
export.create(EnumSet.of(TargetType.DATABASE), metadata.buildMetadata());

Hibernate 5.2 (without warnings):

The above will produce some nasty warnings, which can either be ignored:

Okt 20, 2016 2:57:16 PM org.hibernate.engine.jdbc.connections.internal.ConnectionProviderInitiator initiateService
WARN: HHH000181: No appropriate connection provider encountered, assuming application will be supplying connections
Okt 20, 2016 2:57:16 PM org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator initiateService
WARN: HHH000342: Could not obtain connection to query metadata : The application must supply JDBC connections

... or you work around them by hacking the following ConnectionProvider into the settings (it shouldn't be required in my opinion)

        .applySetting(AvailableSettings.CONNECTION_PROVIDER, new ConnectionProvider() {
            @Override
            public boolean isUnwrappableAs(Class unwrapType) {
                return false;
            }
            @Override
            public <T> T unwrap(Class<T> unwrapType) {
                return null;
            }
            @Override
            public Connection getConnection() {
                return connection; // Interesting part here
            }
            @Override
            public void closeConnection(Connection conn) throws SQLException {}

            @Override
            public boolean supportsAggressiveRelease() {
                return true;
            }
        })

Hibernate 5.0:

MetadataSources metadata = new MetadataSources(
    new StandardServiceRegistryBuilder()
        .applySetting("hibernate.dialect", "org.hibernate.dialect.H2Dialect")
        .build());

// [...] adding annotated classes to metadata here...
metadata.addAnnotatedClass(...);

SchemaExport export = new SchemaExport(
    (MetadataImplementor) metadata.buildMetadata(),
    connection // pre-configured Connection here
);
export.create(true, true);

Hibernate 4:

As a reminder, here's how this worked in Hibernate 4:

Configuration configuration = new Configuration()
    .setProperty("hibernate.dialect", "org.hibernate.dialect.H2Dialect");

// [...] adding annotated classes to metadata here...
configuration.addAnnotatedClass(...);

configuration.generateSchemaCreationScript(
    Dialect.getDialect(configuration.getProperties()));
SchemaExport export = new SchemaExport(configuration, connection);
export.create(true, true);