I've created a pure Java library that does not require a ROS installation, RosJava, or any other non-Java libraries in order to read information and deserialize messages from version 2.0 ROS bag files.  It's useful in environments where you can't or don't want to install ROS, or if you simply want to be able to quickly analyze bag files without any other overhead.

It is available on GitHub at https://github.com/swri-robotics/bag-reader-java and has been deployed to Maven Central (see the GitHub page for package coordinates).

The API and functionality grew organically out of my own needs, so comments on how it could be improved or contributions are welcome.

As far as my own needs go, I developed this library because I've also created a web-based application for cataloging, analyzing, and searching through large  numbers of bag files.  It's not ready for public release yet, but hopefully it will be soon...

-- 
P. J. Reed, Senior Research Analyst
(210) 522-6948
Intelligent Vehicle Systems (http://ivs.swri.org)
Applied Sensing Department (http://appliedsensing.swri.org)
Southwest Research Institute (http://www.swri.org)