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Java 2 Bible Enterprise Edition phần 6

Không có thông báo của tôi Lỗi Go? Trong những ví dụ này, chúng tôi đã được hiển thị mã in ra để System.err hoặc System.out. Sau khi tất cả, mã của bạn được nhúng vào trong một máy chủ Web một nơi nào đó, nó không phải là mặc dù bạn có một dòng lệnh tốt đẹp mà trên đó để xem tất cả các dấu vết ngoại lệ | Chapter 16 Introducing Enterprise JavaBeans passivated state. Where Do My Error Messages Go In these examples we ve been showing the code printing out to System.err or System.out. After all your code is embedded in a Web server somewhere it s not as though you have a nice command line on which to view all the exception traces. So where do they go The answer depends on the EJB server software you are running. For example the reference implementation puts them in the j2ee.home logs machine_name application_name directory. You will need to look up the documentation for your environment for more information. In a future release of the J2EE environment you will be able to use the new Java logging capability included in J2SE 1.4. This will give you even more control over your logging capabilities. However as logs are files logging will still be controlled somewhat by the restrictions placed on EJBs which we outlined earlier in the chapter. Because stateful session beans can have this intermediate step their lifecycle is a little more complex. Figure 16-2 shows the difference. Notice how in comparison to the simple Figure 16-1 that there is an intermediate state. The intermediate state represents the time when your stateful session bean has been passivated. Figure 16-2 The lifecycle of a stateful session bean While your mailer bean does not need to handle passivation there is no state to be saved it will be implemented anyway as an exercise. When the bean is about to be serialized you don t want it to keep any information about the mail system in use. There really isn t any need for it so you might as well remove the reference. The number formatter can stay though because it is not causing you any harm. This makes the ejbPassivate method body really simple public void ejbPassivate mailSession null smtpService null Recovering from passivation activation requires you to undo the effects that you ve just created. Now you must establish those references again. You may .