EntityManagerFactoryProvider.java 文件源码

/**
 * Initializes and returns singleton EntityManagerFactory.
 *
 * @return singleton EntityManagerFactory.
 */
public static EntityManagerFactory getEntityManagerFactory() {
    if (EntityManagerFactoryProvider.entityManagerFactory == null
            || !EntityManagerFactoryProvider.entityManagerFactory.isOpen()) {
        synchronized (EntityManagerFactoryProvider.class) {
            if (EntityManagerFactoryProvider.entityManagerFactory == null
                    || !EntityManagerFactoryProvider.entityManagerFactory.isOpen()) {
                initEntityManagerFactory(DataSourceProvider.getInstance().getDataSource());
            }
        }
    }

    return EntityManagerFactoryProvider.entityManagerFactory;
}