No compiler is provided in this environment. Perhaps you are running on a JRE rather than a JDK?

[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 47.995 s
[INFO] Finished at: 2018-04-11T12:51:26+00:00
[INFO] Final Memory: 210M/483M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project keycloak-common: Compilation failure
[ERROR] No compiler is provided in this environment. Perhaps you are running on a JRE rather than a JDK?
[ERROR] -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException
[ERROR] 
[ERROR] After correcting the problems, you can resume the build with the command
[ERROR]   mvn <goals> -rf :keycloak-common 

Solution:

sudo apt-get install openjdk-8-jdk