JSF backing bean should be serializable?

Question

I'm getting these messages:

[#|2010-07-30T11:28:32.723+0000|WARNING|glassfish3.0.1|javax.faces|_ThreadID=37;_ThreadName=Thread-1;|Setting non-serializable attribute value into ViewMap: (key: MyBackingBean, value class: foo.bar.org.jsf.MyBackingBean)|#]

Do these mean that my JSF backing beans should implement Serializable? Or are they refering to some other problem?

score 65 · Accepted Answer · edited Jun 20 '20 at 09:12

65

Yes, you understood it correctly. The view is basically stored in the session scope. The session scope is in JSF backed by the Servlet's HttpSession. All session attributes are supposed to implement Serializable, this because the average servletcontainer may persist session data to harddisk among others to be able to share with other servers in a cluster, or to survive heavy load, or to revive sessions during server restart.

Storing raw Java objects on harddisk is only possible if the respective class implements Serializable. Then ObjectOutputStream can be used to write them to harddisk and ObjectInputStream to read them from harddisk. The servletcontainer manages this all transparently, you actually don't need to worry about it. JSF is just giving a warning so that you understand the risks.

edited Jun 20 '20 at 09:12

Community

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answered Jul 30 '10 at 15:02

BalusC

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My beans are mostly view scoped. Are they also persisted when the session is persisted? – egbokul Jul 30 '10 at 15:05
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As said, the view is stored in the session. – BalusC Jul 30 '10 at 15:06
Thanks for the clarification! – egbokul Jul 30 '10 at 15:06
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@BalusC, Your JSF,JavaEE answers are valuable. – Sree Rama May 31 '13 at 08:43
@BalusC, should we serialize view beans only or view and session beans ? and what about request and application beans ? – Mahmoud Saleh Dec 24 '13 at 16:57
What about injected resources such as EJB's? Would they be re-injected on ViewScoped Bean been restored and should they be marked as `transient` in this case? – Aleksandr Erokhin Oct 18 '15 at 10:12
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@AlexErohin: EJBs are injected as serializable proxies. No need to change anything here. See also a.o. http://stackoverflow.com/q/25514361 – BalusC Oct 19 '15 at 08:02

score 0 · Answer 2 · answered Jun 22 '15 at 12:15

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Beans that use session, application, or conversation scope must be serializable, but beans that use request scope do not have to be serializable. Source: https://docs.oracle.com/javaee/6/tutorial/doc/gjbbk.html

answered Jun 22 '15 at 12:15

user2823705

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Important note: That section is about CDI managed beans, not JSF managed beans. – BalusC Jun 22 '15 at 12:19
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Could you please elaborate more your answer adding a little more description about the solution you provide? – abarisone Jun 22 '15 at 12:32

score -2 · Answer 3 · answered Jun 22 '15 at 13:44

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Yes, Backing Beans / Managed Beans are basically meant to persist the state of the view, so it should be implemented serialization, but UI Components may not allow it to serializable and JSF Runitime will show you errror/ warning message. one thing you can do is mark such component transient in your MBeans.

Thanks.

answered Jun 22 '15 at 13:44

Ambrish

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This does not apply to request or application scoped JSF managed beans. As to UI components, you should simply never assign an UI component as an instance variable of a managed bean in a scope broader than the request scope. Doing so is simply bad design. See also a.o. http://stackoverflow.com/questions/14911158/ – BalusC Jun 22 '15 at 14:38

JSF backing bean should be serializable?

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