Niels Berglund shows how you can use sp_execute_external_script to run Java code in SQL Server 2019:
In SQL Server 2019 Microsoft added the ability to execute custom Java code along the same lines we execute R and Python, and this blog post intends to give an introduction of how to install and enable the Java extension, as well as execute some very basic Java code. In future posts, I drill down how to pass data back and forth between SQL Server and Java.
There may very well be future posts discussing how the internals differ between Java and R/Python, but I want to talk about that a little bit in this post as well, as it has an impact on how we write and call Java code.
The not-so-secret here is that Java itself is less interesting of a language than, say, Scala. And the reason you’d support Scala? To interact with an Apache Spark cluster. I think that’s a big part of why you’d want the installer to load Java 1.8 instead of 1.9 or later (which contain API changes which break Spark). Definitely give this a careful read, as there are more working parts and more gotchas than R or Python support.