Q. What is WebSphere Application Server?
A. WebSphere Application Server (WAS) is IBM's cross-platform HTTP add-on that provides a secure, transaction-based Web development engine. WAS is a Java-based application server that implements server-side Java solutions such as Java servlets, Enterprise Java Beans (EJBs) and JavaServer Pages.
WAS is evolving as the linchpin in IBM's Java initiative. Not only is WAS cross-platform, but it also provides all the services needed to build scalable, secure transaction-oriented Web applications. WAS is turning out to be the key element in Java's success on the AS/400.
Q. What are Servlets? JavaServer Pages? EJBs?
A. Servlets: Java Servlets are the low end of server-side Java. These Java programs are essentially a Java version of CGI programming. Java servlets provide a simple framework for handling Web requests and responses. Java Servlets typically read data from the HTTP data stream (with either Post or Get) and then write HTML back out to the requesting browser.
JavaServer Pages: JSPs are a cross between HTML and Java -- essentially a way to create a self-generating, or dynamic, HTML page. For example, a JSP may include the Java code to render query results to HTML and the HTML to format those results. When the HTTP server gets a request to process a JSP file, it essentially parses the page and transforms it into a Java servlet on the fly. The standard edition of WAS included with OS/400 can do both Servlets and JavaServer Pages.
Enterprise Java Beans: EJBs are Java's holy grail. They allow you to build distributed, scalable transactional applications using Java. EJBs abstract away much of the low-level details of transaction and state management, security, persistence, multi-threading and resource pooling. EJBs are also platform-independent and can be deployed on multple platforms without recompilation or source code modifications. EJBs require the $7,500 WAS Advanced Edition.
Q. Does WAS provide a programming interface?
A. No. WAS essentially provides Java-related Web plumbing. It doesn't provide an integrated development environment. The terminally patient can write Java code with the AS/400's green-screen file editor (EDTF) and then use OS/400's QSHELL to create Java bytecode.
However, most rational programmers would use PC-based development tools and move the compiled Java applications to the AS/400. Any of the popular Java integrated development environments (including IBM's VisualAge for Java, Symantec's Visual Cafe and Imprise's JBuilder) can be used to create AS/400 Java applications. However, VisualAge for Java provides the most integration with WAS.
You should also be aware of another rather confusingly named product IBM offers called WebSphere Studio for Windows NT, 98 and 95. This $479 retail package includes the Professional Edition of VisualAge for Java, NetObjects Fusion and several other Web development tools.