Home > Articles > Programming > Java

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

2.2 The J2EE Components

To develop distributed components for the J2EE architecture, you need component technologies, APIs, and administrative tools. Let's take a look at each of these categories as they apply to the J2EE architecture and see what they offer to developers.

Enterprise JavaBeans (EJB)

EJB is a component technology that helps developers create business objects in the middle tier. These business objects (enterprise beans) consist of fields and methods that implement business logic. EJBs are the building blocks of enterprise systems. They perform specific tasks by themselves, or forward operations to other enterprise beans. EJBs are under control of the J2EE application server.

Java Servlets

This component technology presents a request-response programming model in the middle tier. Servlets let you define HTTP-specific servlet classes that accept data from clients and pass them on to business objects for processing. Servlets run under the control of the J2EE application server and often extend applications hosted by web servers.

JavaServer Pages (JSP)

A JSP page is a text-based document interspersed with Java code. A JSP engine translates JSP text into Java Servlet code. It is then dynamically compiled and executed. This component technology lets you create dynamic web pages in the middle tier. JSP pages contain static template data (HTML, WML, and XML) and JSP elements that determine how a page constructs dynamic content. The JSP API provides an efficient, thread-based mechanism to create dynamic page content. We provide several JSP clients as example clients to our EJB components in this book. See "Introducing Servlets and JSP" on page 64 in Chapter 3 for a more detailed JSP overview.

Java Naming Directory Interface (JNDI)

JNDI is a standard Java API for accessing different directory and naming services in the presentation tier or middle tier. JNDI lets you access databases and administered objects (queues, topics, etc.) without knowing their specific names or protocols. This makes JNDI an important step in the design of portable enterprise systems. J2EE application servers use JNDI so that clients can "find" needed distributed components or access environment information (such as database resource names or class names) used to customize EJB behavior_.

Java Database Connectivity (JDBC)

JDBC is an API that lets you invoke SQL commands from Java methods in the middle tier. You can use the JDBC API to access a database from either an enterprise bean or from a servlet or JSP page. The JDBC API has an application-level interface for database access, and a service provider interface to attach JDBC drivers to the J2EE platform. In support of JDBC, J2EE application servers manage a pool of database connections. This provides business objects efficient access to database servers. We provide an overview of database fundamentals and JDBC (see "Database Fundamentals" on page 87 and "Introducing JDBC" on page 88 in Chapter 4).

Java Message Service (JMS)

The JMS API lets you perform asynchronous messaging in the presentation and middle tiers. Asynchronous messaging means that clients do not have to wait for a business method to complete. A JMS server stores messages with topic objects for publish-subscribe broadcasts and queue objects for point-to-point communications. JMS lets you implement push/pull technologies in enterprise designs. See "Introducing JMS" on page 372 in Chapter 8 for a JMS overview.

Java Transaction API (JTA)

Under control of the J2EE application server, the JTA provides a standard interface for demarcating transactions in the middle tier. When multiple clients access the same database, it's important to update the data correctly for each read and write operation. The JTA is useful for marking where dependent database operations occur so that they may be committed (written to the database) if successful or rolled back (undone) when there are errors. The J2EE architecture provides defaults for transaction auto commits and rollbacks.

Java API for XML (JAXP)

JAXP lets you read and write text-based XML programs in the presentation and middle tiers. XML is a portable language known to a large number of tools and applications on the web. In the J2EE platform, XML is used extensively with deployment descriptors for J2EE components. As more system services are provided by the J2EE application server (and not coded by developers), developers customize component behavior declaratively using XML.


The JavaMail API lets you send and receive e-mail in the presentation and middle tiers. JavaMail has a service provider interface and an application-level interface for application components to send mail. JavaMail is a valuable part of the J2EE platform because it allows J2EE components to send and receive e-_mails with different protocols.

J2EE Connector API

The Connector API defines a standard for connecting the J2EE platform to systems in the database tier. This includes mainframe transaction processing, database systems, ERP, and legacy applications that are not written in Java. J2EE vendors and systems integrators use the Connector API to create resource adapters, which allow J2EE components to access and interact with a resource manager of another system.

Java Authentication and Authorization Service (JAAS)

JAAS extends the Java 2 platform security architecture to support user-based authorization. This provides a way for a J2EE application to authenticate a specific user or a group of users that wish to run an application.

J2EE Reference Implementation

The Reference Implementation is a noncommercial product from Sun Microsystems that provides a J2EE application server, web server, relational database (Cloudscape), the J2EE APIs, and a set of development and deployment tools. This implementation is made freely available by Sun for demonstrations, prototyping, and educational use. All of the examples in Enterprise JavaBeans Component Architecture have been developed and tested with the Reference Implementation.

Remote Method Invocation (RMI)

RMI, introduced in the Java Development Kit (JDK) 1.1, lets Java programs find and use Java classes residing on remote machines across networks. RMI makes the use of distributed objects within Java programs transparent and easy to use. RMI provides support for the network calls used by Enterprise JavaBeans in the J2EE architecture. RMI hides the nitty-gritty details of network sockets and TCP/IP. It also marshals and unmarshals method arguments and handles exceptions across the network.

Java Interface Definition Language (IDL)

The EJB specification includes a mapping for EJBs to communicate with each other using Common Object Request Broker Architecture (CORBA). Developers use an Interface Definition Language (IDL) to specify interfaces in a Java IDL file. This file defines the methods and fields that must be platform and language independent. The IDL file is compiled with a special compiler that generates the classes necessary to communicate over the network. CORBA and IDL enable Java programs and EJBs to call legacy code written in other languages. This makes it possible, for example, to call member functions in a C++ program running on a Windows machine from an EJB executing on a UNIX system across a network.

  • + 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