I would suggest creating a Splunk Modular Input in Java.This modular input could classload the jar and invoke the main method as defined in the jar manifests "MAIN-CLASS" and output the data to STD OUT which Splunk will read in and index.
Your Modular Input would then be configurable in Splunk Web (execution interval , sourcetype , index, any other custom propertys you define etc..) , just like how you configure TCP/UDP/File inputs.
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