Home > Articles > Programming > Java

  • Print
  • + Share This
Like this article? We recommend

Stateful Session Beans

Stateful session beans are session beans that preserve some state within the EJB specifically associated with its EJB client. The state (a.k.a. conversational state) of a stateful session bean refers to the data stored within the fields (that is, variables) of the bean instance, as well as within any objects the bean holds and those objects' fields and objects, and so on. When an EJB client accesses a stateful session bean at one instant and changes the state of the bean instance, that state must be preserved and assumed by the bean instance at some later instant in which the bean is accessed.

By creating a session bean that is stateful, the container must assume more responsibility and care in how it manages the bean. For starters, stateful session bean instances are associated with clients that create them and therefore cannot simply be plucked at random from a pool to service client requests. In fact, the creation and removal of a stateful session bean by a client is directly related to the creation and removal of stateful session bean instances on the server side. Furthermore, when resources become limited, a container may decide to serialize (that is, passivate) one or more stateful session beans to persistent storage. As resources become available, or, perhaps, upon client request, the passivated bean must be activated and brought into active memory. Thus, stateful session beans require additional special design considerations on the part of the bean developer.

Stateful Session Bean Logical Component Architecture

Figure 2 depicts the basic architecture (ala another UML class diagram) involved in creating stateful session bean components.

Figure 2 Stateful session EJBs.

Public, nonfinal, and nonabstract stateful session bean implementations, such as MyStatefulSessionEJBean, must implement the SessionBean interface, which, in turn, extends the EnterpriseBean interface. Stateful session EJBs also implement public, nonfinal, and nonstatic business-specific methods, such as the someMethod() and anotherMethod() sample methods shown in the figure. As a final note, session bean implementations must also have a public parameterless constructor and should not implement the finalize() method. Finally, stateful session beans may optionally implement the javax.ejb.SessionSynchronization interface to enable the bean to be notified of certain transaction management events.

Stateful Session Bean Interfaces

Because state is important for stateful session beans, the initial state in which such a bean is created could be important. Thus, stateful session beans can be defined with one or more ejbCreate(...) methods that take zero or more input parameters and return a void type. The exact parameters that are passed into such methods are application-specific, but the name of the method must be ejbCreate. Unlike the ejbCreate() invocation on a stateless session bean, stateful session bean ejbCreate() methods are bound to the EJB client that will continue to use that specific EJB instance. Note also that the container calls setSessionContext() on the stateful session bean before any ejbCreate() method is called, as was the case with the stateless session bean.

The invocation of an ejbRemove() method implemented by a session bean indicates that the client to which this session belongs has decided to remove the stateful session bean from servicing any more requests. The container may also invoke ejbRemove() on a bean when a configurable session maximum timeout has expired.

Perhaps the most significant things to consider when designing a stateful session bean are the ramifications of passivation and activation on your bean. As stated earlier, a container passivates your session bean by serializing its contents and writing this information to some persistent storage mechanism. A container does this when active memory resources are becoming scarce and usually employs some sort of least recently used algorithm to determine which specific bean instances should be passivated (although the actual algorithm used is vendor-specific).

Before a container passivates your bean instance, it calls ejbPassivate() on your bean, which your bean must implement. The implementation of ejbPassivate() must clean up any resources that cannot be serialized and persisted, such as database connections and open file handles. Any objects that remain unclosed after ejbPassivate() completes must be passivatable by the container.

When a request for a passivated bean is made, or, perhaps, when resources are again freed, the container activates the bean. That is, the container deserializes the persisted state of the bean and reconstructs the bean in active memory with the state in which it was originally persisted. After the bean state is reconstructed, the container calls ejbActivate() on the stateful session bean implementation, which should reconstruct any resources that were closed during the call to ejbPassivate(). Alternatively, if a certain amount of time has expired while the bean was in persistent storage, the vendor may elect to remove the bean from persistent storage, given some configurable time limit.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020