Java source files

The Java source files can be EJBs, servlets, or other helper classes. The EJBs and servlets can invoke standard Java EE 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 Java EE is an evolving standard, different products can support different versions of Java EE component APIs.