- The client’s view
- Fundamentals of the EJB architecture
- Types of EJB
- Distributed and local EJB semantics
- Anatomy of an EJB
- Principle of operation: session and entity EJBs
- Principle of operation: message-driven EJBs
- The EJB container and its proxies
- Overview of the EJB API
- EJB rules, standards and limitations
- Assembly and deployment
- Configuration
- Summary
3.13 Summary
EJBs are distributable components that operate in the environment of a container. Clients of session and entity EJBs get access to the EJBs via proxy objects that are part of the container. The proxies are normally generated dynamically when the EJB is deployed to the server. The use of proxies and the container allow uniform methods for imposing security and managing transactions, with limited effort on the part of the developer. Clients of message-driven EJBs interact with the container by sending messages through a messaging service. For all types of EJB, the EJB server will attempt to optimize performance and reliability. The techniques it uses to do this should be mostly transparent to the developer. There are a number of EJB products on the market, and this number will almost certainly increase. Commercial products usually offer facilities in addition to these demanded by the EJB Specification, such as load balancing and resource pooling.