Here is a list of my top 10 OpenLiberty hidden features. They are not the “best” features by any means of »hidden knowledge«, but they are the most handy features I use regularly not everyone knows about. YMMV. 😉
Glowroot is a lightweighted but feature-rich java VM agent, which will allow you to collect and evaluate metrics from almost any VM. For larger setups, you might want to install a central collection instance. This guide covers how to set up Glowroot Central on OpenLiberty, a lightweigt and extremely fast Java Application Server (aka Servlet Container).
The java application server OpenLiberty will receive support for Certificates issued by Let’s Encrypt. The setup will be ridiculously easy as always. You can just paste the following lines into your server.xml ein:
Json-B (not JSONB!), short for Json Binding, is a modern MicroProfile Java standard to convert json documents (json messages) to a java class and vice versa.
This standard is supported by most modern java application containers. But because of a definition gap in the Jax-RS standard, it is not as easy as initially thought to get proper and helpful error messages if an invalid JSON document is encountered in the POST request body of an endpoint. The ExceptionMapper will only work after applying a few tricks.