EJB

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Enterprise JavaBeans (EJB) technology is the server-side component architecture for Java Platform, Enterprise Edition (Java EE). EJB technology enables to create distributed, transactional, secure and portable application component objects.

EJB supports the development and deployment of component based business applications. Applications written using the Enterprise JavaBeans architecture are scalable, transactional, and multi-user secure. These applications may be written once, and then deployed on any server platform that supports the Enterprise JavaBeans specification.

EJB History

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EJB Features

Security Management
Persistence Management
Transaction Management
Distributable Interoperable Management
Exception Management

Types of EJB

Session Beans
- StateFull Session Beans
- Stateless Session Beans
Entity Beans
Message Driven Beans

Problems with EJB as a component based development

EJBs are an attempt to create component based application development. With EJBs it is easier to develop components, but the same basic and fundamental maintenance problem will still be there. That is the dependencies between the client and the components. The usage of a component is fixed, changes on the component interface cause to break the client code. The same client/server problem comes back, that is as the users of a component increases the maintenance of that component getting harder and harder until it goes to impossible.

For a true component based application development we need to standardize the usage of a component. The client must somehow flexibly figure out automatically how to use a component, so component changes don't affect any of the clients using that component. Without that flexibility, a true component based application development will remain as an idea, a dream, a theory without significant practical use. If we had that flexibility, it could cause a paradigm shift in the software development industry.

JINI was an attempt from Sun to address this flexibility problem. In JINI, the client download the component interface implementation and execute it in the client space.

So we need to mix (somehow) EJB and JINI technologies to come up with a true flexible component based technology.