package auction.command;import auction.dao.DAOFactory;import javax.ejb.*;/** * The implementation of a generic EJB command handler. *<p> * This implementation injects a data access object factory into * the data access commands. Alternatively, without a DAO layer, * you could inject an EntityManager directly into the data access * commands, and the CommandHandlerBean would get the EntityManager * injected by the EJB container. * * @author Christian Bauer */@Statelesspublic class CommandHandlerBean implements CommandHandler {    // Use lookup of DAOs with a factory    DAOFactory daoFactory = DAOFactory.instance(DAOFactory.HIBERNATE);    @TransactionAttribute(TransactionAttributeType.NEVER)    public Command executeCommand(Command command)            throws CommandException {        command.execute();        return command;    }    @TransactionAttribute(TransactionAttributeType.REQUIRED)    public Command executeCommand(DataAccessCommand command)            throws CommandException {        command.setDAOFactory(daoFactory);        command.execute();        return command;    }}