Home > Articles > Programming > Java

  • Print
  • + Share This
This chapter is from the book

This chapter is from the book

Defining Client Access with Interfaces


The material in this section applies only to session and entity beans, not to message-driven beans. Because they have a different programming model, message-driven beans do not have interfaces that define client access.

A client may access a session or an entity bean only through the methods defined in the bean's interfaces. These interfaces define the client's view of a bean. All other aspects of the bean—method implementations, deployment descriptor settings, abstract schemas, and database access calls—are hidden from the client.

Well-designed interfaces simplify the development and maintenance of J2EE applications. Not only do clean interfaces shield the clients from any complexities in the EJB tier, but they also allow the beans to change internally without affecting the clients. For example, even if you change your entity beans from bean-managed to container-managed persistence, you won't have to alter the client code. But if you were to change the method definitions in the interfaces, then you might have to modify the client code as well. Therefore, to isolate your clients from possible changes in the beans, it is important that you design the interfaces carefully.

When you design a J2EE application, one of the first decisions you make is the type of client access allowed by the enterprise beans: remote or local.

Remote Access

A remote client of an enterprise bean has the following traits:

  • It may run on a different machine and a different Java virtual machine (JVM) than the enterprise bean it accesses. (It is not required to run on a different JVM.)

  • It can be a Web component, a J2EE application client, or another enterprise bean.

  • To a remote client, the location of the enterprise bean is transparent.

To create an enterprise bean with remote access, you must code a remote interface and a home interface. The remote interface defines the business methods that are specific to the bean. For example, the remote interface of a bean named BankAccountEJB might have business methods named debit and credit. The home interface defines the bean's life cycle methods—create and remove. For entity beans, the home interface also defines finder methods and home methods. Finder methods are used to locate entity beans. Home methods are business methods that are invoked on all instances of an entity bean class. Figure 3–2 shows how the interfaces control the client's view of an enterprise bean.

Figure 3-2Figure 3–2 Interfaces for an Enterprise Bean With Remote Access

Local Access

A local client has these characteristics:

  • It must run in the same JVM as the enterprise bean it accesses.

  • It may be a Web component or another enterprise bean.

  • To the local client, the location of the enterprise bean it accesses is not transparent.

  • It is often an entity bean that has a container-managed relationship with another entity bean.

To build an enterprise bean that allows local access, you must code the local interface and the local home interface. The local interface defines the bean's business methods, and the local home interface defines its life cycle and finder methods.

Local Interfaces and Container-Managed Relationships

If an entity bean is the target of a container-managed relationship, then it must have local interfaces. The direction of the relationship determines whether or not a bean is the target. In Figure 3–1, for example, ProductEJB is the target of a unidirectional relationship with LineItemEJB. Because LineItemEJB accesses ProductEJB locally, ProductEJB must have the local interfaces. LineItemEJB also needs local interfaces—not because of its relationship with ProductEJB—but because it is the target of a relationship with OrderEJB. And because the relationship between LineItemEJB and OrderEJB is bidirectional, both beans must have local interfaces.

Because they require local access, entity beans that participate in a container-managed relationship must reside in the same EJB JAR file. The primary benefit of this locality is increased performance—local calls are usually faster than remote calls.

Deciding on Remote or Local Access

The decision regarding whether to allow local or remote access depends on the following factors.

Container-managed relationships: If an entity bean is the target of a container-managed relationship, it must use local access.

Tight or loose coupling of related beans: Tightly coupled beans depend on one another. For example, a completed sales order must have one or more line items, which cannot exist without the order to which they belong. The OrderEJB and LineItemEJB entity beans that model this relationship are tightly coupled. Tightly coupled beans are good candidates for local access. Since they fit together as a logical unit, they probably call each other often and would benefit from the increased performance that is possible with local access.

Type of client: If an enterprise bean is accessed by J2EE application clients, then it should allow remote access. In a production environment, these clients almost always run on different machines than the J2EE server. If an enterprise bean's clients are Web components or other enterprise beans, then the type of access depends on how you want to distribute your components.

Component distribution: J2EE applications are scalable because their server-side components can be distributed across multiple machines. In a distributed application, for example, the Web components may run on a different server than the enterprise beans they access. In this distributed scenario, the enterprise beans should allow remote access.

If you aren't sure which type of access an enterprise bean should have, then choose remote access. This decision gives you more flexibility—in the future you can distribute your components to accommodate growing demands on your application.

Although uncommon, it is possible for an enterprise bean to allow both remote and local access. Such a bean would require both remote and local interfaces.

Performance and Access

Because of factors such as network latency, remote calls may be slower than local calls. On the other hand, if you distribute components among different servers, you might improve the application's overall performance. Both of these statements are generalizations; actual performance can vary in different operational environments. Nevertheless, you should keep in mind how your application design might affect performance.

Method Parameters and Access

The type of access affects the parameters of the bean methods that are called by clients. The following topics apply not only to method parameters, but also to method return values.


An argument in a remote call is passed by value; it is a copy of an object. But an argument in a local call is passed by reference, just like a normal method call in the Java programming language.

The parameters of remote calls are more isolated than those of local calls. With remote calls, the client and bean operate on different copies of a parameter object. If the client changes the value of the object, the value of the copy in the bean does not change. This layer of isolation can help protect the bean if the client accidentally modifies the data.

In a local call, both the client and the bean may modify the same object. In general, you should not rely on this side effect of local calls. Perhaps someday you will want to distribute your components, replacing the local calls with remote ones.

Granularity of Accessed Data

Because remote calls are likely to be slower than local calls, the parameters in remote methods should be relatively coarse-grained. Since a coarse-grained object contains more data than a fine-grained one, fewer access calls are required.

For example, suppose that a CustomerEJB entity bean is accessed remotely. This bean would have a single getter method that returns a CustomerDetails object, which encapsulates all of the customer's information. But if CustomerEJB is to be accessed locally, it could have a getter method for each instance variable: getFirstName, getLastName, getPhoneNumber, and so forth. Because local calls are fast, the multiple calls to these finer-grained getter methods would not significantly degrade performance.

  • + 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.


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.


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.


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.


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


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


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.


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.


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