|Resource Adapters||A standard architecture for connecting the Java2 Enterprise Edition (J2EE) platform to heterogeneous EIS's|
|What's a Resource Adapter||What's an EIS|
Resource Adapter plays a central role in the integration and connectivity
between an EIS and an application server.
It serves as the point of contact between application components, application servers and enterprise information systems (EIS).
A resource adapter, along with the other components, must communicate with one another based on well-defined contracts that are specified by the J2EE Connector Architecture.
|An EIS (Enterprise
Information System) can be thought of as an existing source of enterprise
information, such as an ERP system like the Oracle E-Business Suite,
SAP R/3, a mainframe transaction processing system, or an RDBMS.
EISs are usually not implemented in Java, so the J2EE Connector Architecture provides mechanisms to bring these systems into the J2EE application arena through the specification and use of Resource Adapters, Common Client Interfaces, and Quality of Service contracts.
|What Comprises a Resource Adapter||How does a Resource Adpater work with an EIS|
|To enable seamless integration with an application
server, a resource adapter must abide by guidelines, known as system-level
contracts, that are defined by the Connector
These contracts exist between the application server and the EIS, and are implemented through the Resource Adapter. They also specify how a system external to the J2EE platform can integrate with it by supporting basic functions that are handled by the J2EE container. There are three major categories of these functions:
|A Resource Adapter is specific
to the EIS for which it was developed or purchased. It provides the system
level operations needed to communicate and operate with the EIS.
While a Resource Adapter is specific to the EIS it represents, it is
not specific to a particular application server and can therefore be
reused across any J2EE application server.
The Resource Adapter exposes its capabilities to the application server through a Common Client Interface. Using the exposed Common Client Interface, the application server can effectively incorporate the services of the Resource Adapter into its operations while insulating the applications themselves from the underlying implementation of the EIS.
Important requirements for effective and scalable integration with EISs are system services such as
Resource Adapter Implementation
The J2EE Connector
Architecture specification defines interfaces, which implement
the three contracts summarized above. Most of these interfaces are
mandatory, in that they must be implemented by the adapter, while others
do not need to be implemented.
These non-mandatory interfaces are provided for the developers so they can maintain
a consistent programming model if they choose.
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