EJB来模拟银行ATM机的流程及操作：获取系统属性，初始化JNDI，取得Home对象的引用，创建EJB对象，并将当前的计数器初始化，调用每一个EJB对象的count()方法，保证Bean正常被激活和钝化，EJB对象是用完毕，从内存中清除，从账户中取出amt，如果amt>账户余额抛出异常，一个实体Bean可以表示不同的数据实例，我们应该通过主键来判断删除哪个数据实例-EJB to simulate the process of bank ATM machines and operation: Get system properties, initialize JNDI obtain the Home object' s references to create EJB objects, and the current counter is initialized each EJB object count () method is called, Bean normal activation and passivation, EJB object is used up, cleared from memory, remove from the account amt amt>　account balance throw an exception, an entity Bean can represent different instances of the data, we should be the primary key to judgment delete which data instances