EJB & JSP: Java On The Edge, Unlimited Edition by Lou Marco ISBN: 0764548026 Your Guide to Cutting-Edge J2EE Programming Techniques. Chapter 2: J2EE Component APIs This chapter provides an overview of the J2EE component APIs. As mentioned in Chapter 1, J2EE is a collection of approximately 12 application programming interfaces (APIs) for developing enterprise applications. These APIs define a complete set of services that software engineers use to develop software components. J2EE simplifies the work of an application development team by providing a rich set of services that manage many application details without programming. J2EE API Classifications The J2EE APIs provide numerous services to n-tier application developers. We may group the J2EE APIs into three classifications corresponding to the category of service, or function, the APIs provide to the application development team. The classifications are as follows: . Application components: These include applets, which are Java programs that execute in the client browser; servlets, which execute on the server; and JSP pages, which provide dynamic content to Web pages. J2EE also enables clients to run applications that can access data (by using a database API) without going to a Web server. . Resource managers: These enable customer components to connect to an external component. These external components can be another piece of J2EE, such as JavaMail (for mail messaging) or an IBM mainframe transaction processor (such as IMS or CICS). . Database access: J2EE database access relies on the Java Database Connectivity API or JDBC, which enables a customer container to issue industry-standard SQL. Relational database access in Java also relies heavily on Java Transaction Services, or JTS, and the Java Transaction API. The J2EE APIs work in concert to provide the services mentioned in the aforementioned classifications. For example, a developer would use an application component API, such as JSP, to create a Web interface for an application that accesses data from a relational database using JDBC. In the following section, we ll take a look at J2EE APIs that fall within the preceding classifications.
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