How to load a SpEL expression into logback-spring.xml

Question

I have a SpEL expression in my application.properties file that I'm trying to load into my logback-spring.xml file. I have printed the SpEL expression, so I know it evaluates correctly. But the logback keeps printing the SpEL instead of evaluating it.

In my prop file, I have

user.name= #{user.firstName.concat(' ').concat(user.lastName)}

And in my logback file, I have

<springProperty scope="context" name="user_name" source="user.name" />
...
<pattern>name=${user_name} %msg%n </pattern>

Instead of printing the name, it prints "name=#{user.firstName.concat(' ').concat(user.lastName)}"

I have another value loaded from my prop file (not a SpEL expression), and that one works correctly. So I know the mistake I'm making is that I'm not making the logback file evaluate the expression

Answer 1

Spring logback extensions which are active in a logback-spring.xml file do not support SPEL expression evaluation. The only features supported are described here: https://docs.spring.io/spring-boot/docs/current/reference/html/features.html#features.logging.logback-extensions

Also, your assumption about SPEL evaluation in properties files seems to be incorrect:

SpEL expressions from application property files are not processed at time of parsing these files and populating the environment.

( https://docs.spring.io/spring-boot/docs/current/reference/html/features.html#features.external-config.typesafe-configuration-properties.vs-value-annotation )