It'a always fun with PDI and especially when you put fingers on qwerty for something cool!!
Here will show you, how to define connection via "project.properties" [ie foo.properties] and not fetching those information from kettle.properties [those who are familiar with Pentaho's Data Integration]. This is pretty much useful and always a best practice in ETL development, when you are working on multiple projects and working in many connections.
Directory Structure: Below is C:\pentaho_projects
Demo Job Snapshot:
Executing one transformation to set these above entries from foo.properties and another transformation using those to retrieve a database table. Sweet Aha :)
Now once the Setting variables is set you can use in creating a database connection and that is being used under "fetch employee info".
Fetch Employee Info Transformation using "foo_Project" conncetion
