In Spring
Javadoc:
"existing configuration makes use of the "systemPropertiesMode" and/or "systemPropertiesModeName" properties. Users are encouraged to move away from using these settings, and rather configure property source search order through the container's Environment"
Why is it encouraged to search through container's Environment?
EDIT:
Need to understand why to use @PropertySource instead of PropertyPlaceholderConfigurer, what benefits does PropertySource gives over PropertyPlaceholderConfigurer if both achieve the goals of fetching resources mentioned through the path.