Is there a JDBC Driver for Microsoft SSAS Tabular Databases?
There used to be a OLAP JDBC driver that supported SSAS called olap4j but it has not been updated in a while and I am not sure of its support for anything above 2012. It is always worth a try though.

Communication with an SSAS instance is done using XMLA , which itself is based upon the SOAP protocol. Technically you should be able to send queries using a standard SOAP client with embedded XMLA statements.

That being said, I know that Microsoft uses a proprietary implementation for their SOAP over TCP/IP so you may need to tinker with your client to get it to work.

Some additional detail is given in FrankPI's answer on StackOverflow where somebody asked a similar question and there is even a suggestion open for Power BI that requests interoperability between Java and SSAS.

If none of the above solutions work for you I am afraid you will have to roll your own or use the supported ADOMD.NET components.