As per the Salesforce Spring `11 release notes:
#In API version 21.0, WSC (Web Service Connector) replaces Apache Axis 1.3 as the preferred SOAP Java client framework.
WSC is an open-source project and contains a command utility that generates Java source and bytecode files from WSDL
files. The Java samples illustrating use of API calls for the API, and Metadata API have been rewritten in the Web Services
API Developer's Guide..#
It would be good to move the Salesforce plugins to use the new framework, for performance and maintainability perspectives.
API Versions: https://na14.salesforce.com/services/data