12 Chapter (Web design portfolio) 1 Rapid application development. Your
12 Chapter 1 Rapid application development. Your application can be constructed faster because you get middleware infrastructure services such as transactions, pooling, security, and so on from the application server. There s also less of a mess to maintain. Note that while EJB does have these virtues, there are also scenarios in which EJB is overkill. See Chapters 11 and 16 for best practices and discussion surrounding the issue of when to (and when not to) use EJB. Physically, EJB is actually two things in one: A specification. This is a 640-plus-page Adobe Acrobat PDF file, freely downloadable from http://java.sun.com/products/ejb/docs.html. This specification lays out the rules of engagement between components and application servers. It constricts how you code enterprise beans to enable write once, run anywhere behavior for your EJB application. A set of Java interfaces. Components and application servers must conform to these interfaces. Since all components are written to the same interfaces, they all look the same to the application server. The application server therefore can manage anyone s components. Why Java? EJB architecture has supported only the Java language thus far. Though this sounds a bit restrictive, the good news is that Java is one of the best-suited languages for building components for the following reasons. Interface/implementation separation. We need a language that supports clean separation between the interface and implementation mainly to keep the component upgrades and maintenance to minimum. Java supports this separation at a syntactic level through the interface and class keywords. Safe and secure. The Java architecture is much safer than traditional programming languages. In Java, if a thread dies, the application stays up. Pointers are no longer an issue. Memory leaks occur much less often. Java also has a rich library set, so that Java is not just the syntax of a language but a whole set of prewritten, debugged libraries that enable developers to avoid reinventing the wheel in a buggy way. This safety is extremely important for mission-critical applications. Sure, the overhead required to achieve this level of safety might make your application slower, but 90 percent of all business programs are glorified graphical user interfaces (GUIs) to databases. That database is going to be your number one bottleneck, not Java.
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