Implementing and Generating Proxies in Application Systems 
Proxies are non-language-specific interface descriptions in WSDL. The generation converts these descriptions into executable proxies in application systems.
Procedure
To generate proxies in an application system based on AS ABAP, use the ABAP proxy generation. Generation takes place in AS ABAP.
ABAP proxy runtime supports the WS and the XI protocol.
More information about XI runtime: XI-Specific ABAP Proxy Runtime Protocols
To generate proxies in an application system based on AS Java, use the Java proxy generation in SAP NetWeaver Developer Studio for new implementations.
More information: Creating and Configuring XI 3.0-Compatible Web Service Providers
You can still use the Java proxy generation in Integration Builder. However, it is no longer supported in subsequent releases.
More information: Java Proxy Objects (XI 3.0-Compatible)