Important Java Libraries

1. Jackson :

Jackson is a very popular and efficient java based library to serialize or map java objects to JSON and vice versa

https://www.tutorialspoint.com/jackson/jackson_overview.htm

Example:

https://www.mkyong.com/java/jackson-2-convert-java-object-to-from-json/

2. Saxon XSLT

Saxon is an XSLT and XQuery processor created by Michael Kay and now developed and maintained by his company, Saxonica. There are open-source and also closed-source commercial versions. Versions exist for Java, JavaScript^[1] and .NET.

Details list is available here:

https://javarevisited.blogspot.com/2018/01/top-20-libraries-and-apis-for-java-programmers.html