https://github.com/javaee/jpa-spec: Java(TM) Persistence API 
Copyright (c) 2008 - 2013 Oracle Corporation. All rights reserved.
This program and the accompanying materials are made available under the
terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
which accompanies this distribution.
The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
and the Eclipse Distribution License is available at
http://www.eclipse.org/org/documents/edl-v10.php.
Contributors:
    Linda DeMichiel - Java Persistence 2.1
    Linda DeMichiel - Java Persistence 2.0

/*******************************************************************************
 * Copyright (c) 2008 - 2013 Oracle Corporation. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *     Linda DeMichiel - Java Persistence 2.1
 *     Linda DeMichiel - Java Persistence 2.0
 *
 ******************************************************************************/ 
package javax.persistence.metamodel;

import java.util.Set;


Provides access to the metamodel of persistent
entities in the persistence unit. 

Since:Java Persistence 2.0
/**
 * Provides access to the metamodel of persistent
 * entities in the persistence unit. 
 *
 * @since Java Persistence 2.0
 */
public interface Metamodel {

    
 Return the metamodel entity type representing the entity.
 @param cls  the type of the represented entity
 @return the metamodel entity type
 @throws IllegalArgumentException if not an entity

/**
     *  Return the metamodel entity type representing the entity.
     *  @param cls  the type of the represented entity
     *  @return the metamodel entity type
     *  @throws IllegalArgumentException if not an entity
     */
    <X> EntityType<X> entity(Class<X> cls);

    
 Return the metamodel managed type representing the 
 entity, mapped superclass, or embeddable class.
 @param cls  the type of the represented managed class
 @return the metamodel managed type
 @throws IllegalArgumentException if not a managed class

/**
     *  Return the metamodel managed type representing the 
     *  entity, mapped superclass, or embeddable class.
     *  @param cls  the type of the represented managed class
     *  @return the metamodel managed type
     *  @throws IllegalArgumentException if not a managed class
     */
    <X> ManagedType<X> managedType(Class<X> cls);
    
    
 Return the metamodel embeddable type representing the
 embeddable class.
 @param cls  the type of the represented embeddable class
 @return the metamodel embeddable type
 @throws IllegalArgumentException if not an embeddable class

/**
     *  Return the metamodel embeddable type representing the
     *  embeddable class.
     *  @param cls  the type of the represented embeddable class
     *  @return the metamodel embeddable type
     *  @throws IllegalArgumentException if not an embeddable class
     */
    <X> EmbeddableType<X> embeddable(Class<X> cls);

    
 Return the metamodel managed types.
 @return the metamodel managed types

/**
     *  Return the metamodel managed types.
     *  @return the metamodel managed types
     */
    Set<ManagedType<?>> getManagedTypes();

    
Return the metamodel entity types.

Returns:the metamodel entity types
/**
     * Return the metamodel entity types.
     * @return the metamodel entity types
     */
    Set<EntityType<?>> getEntities();

    
Return the metamodel embeddable types.  Returns empty set
if there are no embeddable types.

Returns:the metamodel embeddable types
/**
     * Return the metamodel embeddable types.  Returns empty set
     * if there are no embeddable types.
     * @return the metamodel embeddable types
     */
    Set<EmbeddableType<?>> getEmbeddables();
}