1Component Replication in Distributed Systems: a Case study using Enterprise Java Beans

A recent trend has seen the extension of object-oriented middleware to component-oriented middleware. A major advantage components offer over objects is that only the business logic of an application needs to be addressed by a programmer with support services required incorporated into the application at deployment time. This is achieved via components (business logic of an application), containers that host components and are responsible for providing the underlying middleware services required by components (such as persistence) and application servers that host containers. Well-known examples of component middleware architectures are Enterprise Java Beans (EJBs) and the CORBA Component Model (CCM). Services available at deployment time in most component architectures are component persistence (typically using databases) and atomic transactions (for ensuring the consistency of component state). This paper examines, using EJBs, how replication for availability can be supported by containers so that components that are transparently using persistence and transactions can also be made highly available