I have logback.xml with appender pattern:
%d

host:${host} [%thread] %-5level %logger

- %msg%n

I have "-Dhost=local" system property also.

The result log message is:
12:47:11.663 host:${host} [main] INFO ...

But I expected:
12:47:11.663 host:local [main] INFO ...

If I set appender pattern to: "host: ${host}", space after colon then all works fine.