By: aathishankaran Printer Friendly Format
thin-client multi-tiered applications are hard to write because they involve
many lines of intricate code to handle transaction and state management,
multithreading, resource pooling, and other complex low-level details.
component-based and platform-independent J2EE architecture makes J2EE
applications easy to write because business logic is organized into reusable
components. In addition, the J2EE server provides underlying services in the
form of a container for every component type. Because you do not have to develop
these services yourself, you are free to concentrate on solving the business
problem at hand.
are the interface between a component and the low-level platform-specific
functionality that supports the component. Before a Web, enterprise bean, or
application client component can be executed, it must be assembled into a J2EE
application and deployed into its container.
assembly process involves specifying container settings for each component in
the J2EE application and for the J2EE application itself. Container settings
customize the underlying support provided by the J2EE server, which includes
services such as security, transaction management, Java Naming and Directory
Interface (JNDI) lookups, and remote connectivity. Here are some of the
security model lets you configure a Web component or enterprise bean so that,
only authorized users access system resources.
transaction model lets you specify relationships among methods that make up a
single transaction so that all methods in one transaction are treated as a
lookup services provide a unified interface to multiple naming and directory
services in the enterprise so that application components can access naming and
remote connectivity model manages low-level communications between clients and
enterprise beans. After an enterprise bean is created, a client invokes methods
on it as if it were in the same virtual machine.
fact that the J2EE architecture provides configurable services means that
application components within the same J2EE application can behave differently
based on where they are deployed.
example, an enterprise bean can have security settings that allow it a certain
level of access to database data in one production environment and another level
of database access in another production environment.
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