EJB客户端从来不直接处理bean实例，他们通常是从容器通过EJBOBject处理。容器对于实例池是开放的，然后在需要的时候重用bean class的实例并对客户端隐藏实现的具体细节。-EJB client never directly deal with bean instance, they are usually from the container through EJBOBject treatment. Container for instance pool is open, and then reused when needed bean class instance and the client hide implementation details.