Java Beans are reusable components and do not have strict specifications for Java Beans. In theory, any Java class can be a bean. But usually, since Java Beans are created by containers (such as Tomcat), Java Beans should have a constructor without parameters. In addition, Java Beans usually implement the Serializable interface to achieve the persistence of the Bean. Java Bean is actually equivalent to a local in-process COM component in the Microsoft COM model, and it cannot be accessed across processes. Enterprise Java Bean is equivalent to DCOM, that is, distributed components. It is based on Java's remote method call (RMI) technology, so EJB can be accessed remotely (cross-process, cross-computer). But EJB must be deployed in containers such as Webspere, WebLogic, and EJB customers never directly access real EJB components, but access through their containers. EJB containers are agents of EJB components, and EJB components are created and managed by containers. The client accesses the real EJB component through the container.