Resource files under the src/main/resources directory are copied verbatim to the target/classes directory during build. But resources can be filtered by turning on filtering in pom.xml:

When filtering is turned on, constructs like ${...} are replaced with actual values if they are defined. For example, create a file test.properties:

The build command "mvn package" simply copies test.properties to target/classes/. But if you build with:

the contents of target/classes/test.properties becomes:


Sometimes you want different resource definitions for different environments, e.g., dev vs. prod. You can achieve that by defining profiles in pom.xml:

In the above, dev is the default profile, prod is defined but not active unless you specifically activate it. With the above profile:

1. the command "mvn package" changes the contents of target/classes/test.properties to:
   

   project.stage=Development
   

   
   
2. if you activate the prod profile with "mvn -P prod package", the contents of target/classes/test.properties becomes:
   

   project.stage=Production
   

   
   
3. system properties overrides values defined in profiles. The command "mvn -Dproject.stage=dev package" creates target/classes/test.properties with contents:
   

   project.stage=dev
   

   
   
4. You can active both dev and prod profiles with:
   

   mvn -P dev,prod package
   

   
   but what will the output be?
   

You can check active profiles with: