How to include spring properties

[vy]

How to include spring properties

[vy]

log4j2-logstash-layout uses Log4j 2 Lookups under the hood and basically provides access to environment variables, certain Java runtime constants (version, OS, etc.) and so on. (See the link for details.) So your question boils down to "Can I access Spring variables from Log4j 2 configuration?". Below I listed approaches I know of you can purpose for the problem:

Read Spring properties file in Log4j 2 configuration

The steps are detailed in this SO post. In a nutshell, add the following to your log4j2.xml:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn">
    <Properties>
        <property name="spring-profile">${bundle:application:spring.profiles.active}</property>
    </Properties>
    <!-- ... -->
</Configuration>

And use ${spring-profile} variable in your layout JSON.

Set system property at application start-up

At Spring application start-up, you expose the Spring property to the rest of the application:

@SpringBootApplication
public class DemoSpringAppApplication {

    @Autowired
    public DemoSpringAppApplication(@Value("${spring.profiles.active}") String profile) {
        System.setProperty("spring.profiles.active", profile);
    }

    // ...

}

Tell Log4j 2 about this property:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn">
    <Properties>
        <property name="spring-profile">${sys:spring.profiles.active}</property>
    </Properties>
    <!-- ... -->
</Configuration>

Thereafter you can access the variable in your layout JSON via spring-profile.

You might be wondering though, why don't we just type ${sys:spring.profiles.active} in our layout JSON? Why do we need a property definition? log4j2-logstash-layout initially tries to resolve variables and if it fails, treats the value as a literal. Given Spring sets the property after Log4j initialization, it becomes too late to resolve the variable and it gets injected as is. To overcome this, we first declare the variable in a property and then access that property via ${spring-profile}. Note that using the same property name (that is, ${spring.profiles.active} rather than ${spring-profile}) yields to an infinite lookup loop.

Set property via -Dspring.profiles.active

If you set the property via -Dspring.profiles.active, then you can directly access it in layout JSON via ${sys:spring.profiles.active}.

Set property as an environment variable shared by both Spring and Log4j 2

I assume title is self-explanatory.

[sabareeshkkanan]

Appreciate for the detailed answer, The first solution errored out by saying cant find the bundle for application, might be related to how it is deployed. So i opted for second solution and worked like charm, and third solution would have worked as well but while developing it is defaulted to an environment. Again thanks

[vy]

@sabareeshkkanan, I am glad at least one of the methods worked for you. Further I created a Gist with a sample Spring Boot application which employs the 1st (the one that did not work for you) and 2nd aforementioned approaches. Hope it helps.