Enterprise JavaBeans (EJB) is a server-side component model for transaction aware, distributed enterprise applications written in the Java programming language. Enterprise JavaBeans 2.1 details the architecture of the Enterprise JavaBeans component model. After an introduction to the component paradigm, the EJB architecture basics are introduced. Based on that, the different component types (Session-, Entity- and Message-Driven-Beans) are discussed in detail. An in-depth introduction to the Java Message Service (JMS) is provided to understand the ideas behind asynchronous and parallel processing provided through Message-Driven-Beans. Transactions, security, and the newly introduced timer service round up the book. Enterprise JavaBeans 2.1 also discusses topics beyond the specification, e.g. inheritance, coupling of EJB components, quality assurance, and more. After reading this book, readers will know the benefits and the limits of EJB. The authors also impart the knowledge required for turning business requirements into EJB-based applications.