Sun Java System Application Server Platform Edition 8.2 Upgrade and Migration Guide

Java Source Files

The Java source files can be EJBs, servlets, or other helper classes. The EJBs and servlets can invoke standard J2EE services directly. They can also invoke methods defined in helper classes. Java source files are used to encode the business layer of applications, such as EJBs. Vendors bundle several services and proprietary Java API with their products. The use of proprietary Java APIs is a major source of non-portability in applications. Since J2EE is an evolving standard, different products can support different versions of J2EE component APIs. This is another aspect that migration addresses.