SAP Java Connector 
Purpose
SAP Java Connector (SAP JCo) is a middleware component that enables the development of SAP-compatible components and applications in Java. SAP JCo supports communication with the SAP Server in both directions: inbound calls (Java calls ABAP) and outbound calls (ABAP calls Java).
SAP JCo can be implemented with Desktop applications and with Web server applications.
SAP JCo is used as an integrated component in the following applications:
● SAP Business Connector, for communication with external Java applications
● in the Application Server, for connecting the integrated J2EE server with the ABAP environment.
SAP JCo can also be implemented as a standalone component, for example to establish communication with the SAP system for individual online (web) applications.
Implementation Considerations
SAP provides SAP Java Connector in a number of different versions:
● as a standalone software component that can be installed independently of the SAP system. You can access the installation files at service.sap.com/connectors.
For client applications in a standalone scenario, you can also use SAP Java
Resource Adapter (SAP JRA) instead of SAP JCo. SAP JRA offers a number of benefits (see 
SAP JRA for Client
Applications).
● SAP JCo is automatically installed (integrated version) when you use the SAP Business Connector or AS Java.
More Information
● SAP JCo Architecture (Standalone Version)
●
SAP JCo Application
Scenarios