SAP Java Resource Adapter 
Purpose
SAP Java Resource Adapter (SAP JRA) is a J2EE -compatible connector for SAP systems. It enables the integration of SAP systems with J2EE application servers. SAP JRA implements the standard J2EE interfaces for SAP Java Connector (SAP JCo), thus simplifying communication between heterogeneous, distributed J2EE landscapes and SAP.
You can use SAP
JRA to call remote functions of an SAP system by executing 
RFC calls via TCP/IP.
Implementation
SAP JRA is an add-on for SAP JCo. It is delivered together with SAP Web AS as a sapjra.rar file. You can find this file in the installation directory.
//<SAPJ2EE Engine Installation>/usr/sap/<System ID>/sys/global/ra/sapjra.rar.
The .rar file contains the Java classes used in SAP JRA.
At present, the J2EE Connector Architecture 1.0 specifications are implemented. For more information on J2EE and the J2EE Connector Architecture, go to java.sun.com/j2ee.
Restrictions
Incoming communication is not supported by SAP JRA at present.
Additional Information
·
SAP JRA for Client
Applications
·
SAP JRA Development
Guidelines
In the Business Intelligence (BI) area, SAP offers various resource adapters that can be used with the BI Java SDK. These enable the applications that you develop with the BI Java SDK to communicate with heterogeneous data sources.