Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin (default-compile) on project: Fatal error compiling: tools.jar not found

You need to set eclipse's default installed "jre" to a jdk. Eclipse Window Menu => Preferences => enter search string "jre" in left navigation pane => click on "Installed JREs" in left navigation pane => Click Add and browse to your JDK. => click the check box next to the JDK to make it default.

You may need to download and install the java jdk if you don't already have it.

Also ensure the eclipse run configuration is set to use the default jdk you set up: Run Menu => Run Configurations => Select the run config for your project (Maven Build) => Click JRE tab => Under Runtime JRE select "workspace default".