Hibernate UUID keeper for import

UUIDKeeperGenerator.java

package fr.mikaelkrok.hibernate;

import java.io.Serializable;
import java.util.Properties;

import org.hibernate.engine.spi.SessionImplementor;
import org.hibernate.id.UUIDGenerator;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.type.Type;

/**
 * Allows to keep UUID while new objects are passed. Based on
 * http://stackoverflow.com/a/5392349/566434.
 * Used  with
 * <pre>
 *   @Id
 *   @Getter
 *   @Setter
 *   @GeneratedValue(generator = UUIDKeeperGenerator.GENERATOR_STRATEGY)
 *   @GenericGenerator(name = UUIDKeeperGenerator.GENERATOR_STRATEGY, strategy = UUIDKeeperGenerator.GENERATOR_CLASS_NAME)
 *   private String id;
 *
 * </pre>
 */
public class UUIDKeeperGenerator extends UUIDGenerator {

    /**
     * Generator strategy.
     */
    public static final String GENERATOR_STRATEGY = "uuid-keeper";

    /**
     * Generator class name.
     */
    public static final String GENERATOR_CLASS_NAME = "com.cegedim.next.servicedirectory.core.model.UUIDKeeperGenerator";

    private String entityName;

    @Override
    public void configure(final Type type, final Properties params, final ServiceRegistry serviceRegistry) {
        this.entityName = params.getProperty(ENTITY_NAME);
        super.configure(type, params, serviceRegistry);
    }

    @Override
    public Serializable generate(final SessionImplementor session, final Object object) {
        Serializable id = session.getEntityPersister(this.entityName, object).getIdentifier(object, session);
        if (id == null) {
            return super.generate(session, object);
        }
        else {
            return id;
        }
    }

}