我在javaweb表单中编写了一个简单的程序，但收到以下错误:WELD-000072Managedbeandeclaringapassivatingscopemustbepassivationcapable.Bean:ManagedBean[classBeanPakage.DemoBeans]withqualifiers[@Any@Default@Named]谁能告诉我这个错误来自哪里？importjavax.enterprise.context.SessionScoped;importjavax.inject.Named;@Named("DemoBeans")@SessionScop