Unknown lifecycle phase - You must specify a valid lifecycle phase or a goal in the format

When running the exec:java goal or any other goal from the command line, you need to ensure the command syntax is correct.

Ensure that you are using double quotes around all property names and property values.

Example - Correct Command Syntax

mvn compile
mvn exec:java -D"exec.mainClass"="dev.selenium.getting_started.FirstScript"