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Category: IT Stuff

JAX-RS: getting helpful Json-B error messages

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.

btrfs raid1 to combine two separate partitions

A btrfs raid1 means mirroring all data and meta data on file system level. If you ever found some of your data lost after a btrfs scrub, you might know this output:

scrub status for <UUID>
  scrub started at Thu Dec 25 15:19:22 2014 and was aborted after 89882 seconds
  total bytes scrubbed: 1.87TiB with 4 errors
  error details: csum=4
  corrected errors: 0, uncorrectable errors: 4, unverified errors: 0

If you happen to have free space on a spare disk left, you can circumvent these problems via a btrfs raid1 on filesystem level. The following article will help you migrate.

Guacamole Liberty Profile Stack on systemd

If you are using Apache Guacamole to access your computers via VNC, RDP or SSH, you might be interested on how to run this web application (war file) as Guacamole Liberty Profile Stack (i.e. on IBM Websphere Liberty Profile). Additionally, you can start the IBM server with systemd to see the console logs in journalctl. Although Liberty Profile is a licenced and proprietary product by IBM, it is free of charge for non-production purposes and development.