What is the major difference between maven `-f` and `-pl` parameters?

Question

When executing mvn test -f file-directory and mvn test -pl project. What is the difference in internal execution of the both ?

Answer 1

From mvn -help

 -f,--file <arg>                        Force the use of an alternate POM
                                        file.

 -pl,--projects <arg>                   Comma-delimited list of specified
                                        reactor projects to build instead
                                        of all projects. A project can be
                                        specified by [groupId]:artifactId
                                        or by its relative path.

Example Usage:

• -f
  • If you want to build a Maven project but you are running Maven from a directory other than the directory which contains the pom.xml for that project.
  • If (for some reason) your POM file is not named pom.xml
• -pl
  • If you want to build a Maven build focussing on a sub set of the parent project's sub modules
  • If you want to resume a multiple module Maven build from the point at which a previous build failed

Given this project structure ...

+- tools
| |
| +- build
| |
+- projects
| |
| +- parent
|    |
|    +- pom.xml
|  
| +- childA
|    |
|    +- pom.xml
| +- childB
|    |
|    +- pom.xml

You could ...

• Build the parent project from the tools/build directory by using -f e.g.
  • cd tools/build; mvn -f ../../projects/parent/pom.xml
• Build only the childA sub module from the tools/build directory by using -f and -pl e.g.
  • cd tools/build; mvn -f ../../projects/parent/pom.xml -pl parent:childA
• Build only the childB sub module from the parent directory by using -pl e.g.
  • cd projects/parent; mvn -pl parent:childB