An applications server provides middleware services to the applications, such as transaction services, security services and others. These services are needed for the applciations to be scalable, robust and secure for multiple concurrent users.

The EJB container :

The EJB container provides a playground where the enterprise beans can run. There can be many beans running within a container. Beans containers are responsible for managing the beans running within them. They interact with the beans calling a few required methods that the bean must expose. Containers may also provide access to legacy system.

The EJB server :

The EJB server provides a runtime environment for one or more containers. EJB servers manage low-level system resources, allocating resources to containers as they are needed. EJB specification does not exactly demonstrate differences between an EJB container and EJB server. They go hand by hand.

The services that Implicit distributed transaction management provide :

Implicit distributed transaction management transactions allow us to perform robust, deterministic operations in a distributed environment by setting attributes on the enterprise beans. The EJB server provides a transaction service a low-level implementation of transaction management and coordination. The transaction service must be exposed throught the Java Transaction API(JTA). The JTA is a high-level interface that we can use to control transactions.

Implicit Security :

Security is a majour consideration for multitier deployments. The Java2 platform Standard Edition yields a robust security service that can authorize and authenticate users, securing deployments from unwanted visitors. EJB adds to this the notion of transparent security, allowing components to reap the benefits of a secure deployment without necessarily coding to a security API.

Implicit resource management and component life cycle:

The EJB server implicityly manages the resources for the components such as threads, sockets and database connections. The life cycle of the components themselves are also managed, allowing for components to be reused by the EJB server as necessary.

Implicit persistence:

Persistence is a natural requirement of any deployment that requires permanent storage. EJB offers assistance hereby automatically saving persistent object data to an underlying storage and retrieving that data at a later time.

Implicit remote accessibility :

EJB products will automatically convert our stand-alone, network-less components into distributed, network-aware beings,

Implicit multiclient support:

EJB servers automatically route concurrent requests from client. EJB servers provide built-in thread support, instantiating multiple copies of your component as necessary and channeling client requests to those instances.