How to get Environment properties from application.properties into logback.groovy in Spring Boot project?

Question

Trying to inject properties defined in application.properties/application.yml into logback.groovy script in Spring Boot proje

Answer 1

logback.groovy needs to be evaluated very early because otherwise the code for loading the spring configuration, instantiating beans, etc. could not log anything. That's why @Inject can't work.

I see 2 options:

1. You could easily load application.properties in logback.groovy, but it's far from trivial to take all the configuration override mechanisms that spring provides into account
2. Create a spring bean that changes the logback configuration programmaticaly when initialized

A different approach is to externalize the logback configuration on production with -Dlogback.configurationFile=/path/to/config.groovy. Putting the config file in a well known location (like /etc/my-app) makes it easy to change log levels in production without re-deploying (or even re-starting).

Answer 2

Sorry to resurrect this thread but while since this is thread is what I found while looking for a solution, I wanted to share a workaround.

I have used a Custom converter and conversion rule to pull out properties in classpath resource (i.e. application.properties):

In logback.groovy:

conversionRule('springApplicationName', CustomSpringApplicationNameConverter)

def patternExpression = '%green([%d{YYYY-MM-dd HH:mm:ss.SSS}]) [%t] %highlight(%-5level) %magenta([%springApplicationName]) - %cyan(%logger{36}) -- %msg%n'

and then 'patternExpression' used in desired appender

and my custom converter class (in groovy):

class CustomSpringApplicationNameConverter extends ClassicConverter {

    @Override
    String convert(ILoggingEvent event) {
        ClassPathResource classPathResource = new ClassPathResource('application.properties')

        Properties applicationProperties = new Properties()
        applicationProperties.load(classPathResource.inputStream)

        String springApplicationName = applicationProperties.getProperty('spring.application.name')
        if (!springApplicationName) {
            System.err.println('Could not find entry for \'spring.application.name\' in \'application.properties\'')
        }

        springApplicationName
    }
}