Properties files and Messages

The Messages.properties and config_fr.properties files are there to provide users with i18n internationalization, as described here:

https://wiki.jenkins-ci.org/display/JENKINS/Internationalization

There is some more detail on localization and internationalization at this link:

http://www.w3.org/International/questions/qa-i18n

In Jenkins plugin development, all we really need to do is provide config_LOCALE.properties files to cater to each language. For example, if the user's LOCALE variable is set to fr, the messages in the config_fr.properties file will be used—other LOCALE files can be added as desired to support other languages.

Your plugin code is able to use and refer to the properties at runtime, as follows:

Messages.GravenBuilder_Task()

The Messages.java class in the target directory is generated at build time, based on these properties files.