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.spi;

import java.util.List;


Determine the list of persistence providers available in the 
runtime environment.

 Implementations must be thread-safe.

 Note that the getPersistenceProviders method can potentially
be called many times: it is recommended that the implementation
of this method make use of caching.

See Also:
  • PersistenceProvider
Since:Java Persistence 2.0
/**
 * Determine the list of persistence providers available in the 
 * runtime environment.
 * 
 * <p> Implementations must be thread-safe.
 *
 * <p> Note that the <code>getPersistenceProviders</code> method can potentially
 * be called many times: it is recommended that the implementation
 * of this method make use of caching.
 *
 * @see PersistenceProvider
 * @since Java Persistence 2.0
 */
public interface PersistenceProviderResolver {

    
Returns a list of the PersistenceProvider implementations 
available in the runtime environment.

Returns:list of the persistence providers available 
        in the environment
/**
     * Returns a list of the <code>PersistenceProvider</code> implementations 
     * available in the runtime environment.
     *
     * @return list of the persistence providers available 
     *         in the environment
     */
    List<PersistenceProvider> getPersistenceProviders();

    
Clear cache of providers.

/**
     * Clear cache of providers.
     *
     */
    void clearCachedProviders();
}