Accessing the application properties in logback.xml

Question

Is it possible to access application properties of spring boot in log back xml.

application.properties

dummy.property=hello
<         


        

Answer 1

If you name your configuration file logback-spring.xml, rather than logback.xml, you can use <springProperty> to access properties from Spring's environment including those configured in application.properties. This is described in the documentation:

The tag allows you to surface properties from the Spring Environment for use within Logback. This can be useful if you want to access values from your application.properties file in your logback configuration. The tag works in a similar way to Logback’s standard tag, but rather than specifying a direct value you specify the source of the property (from the Environment). You can use the scope attribute if you need to store the property somewhere other than in local scope.

<springProperty scope="context" name="fluentHost" source="myapp.fluentd.host"/>
<appender name="FLUENT" class="ch.qos.logback.more.appenders.DataFluentAppender">
    <remoteHost>${fluentHost}</remoteHost>
    ...
</appender>

Answer 2

According to the http://logback.qos.ch/manual/configuration.html#variableSubstitution

Variables can be defined one at a time in the configuration file itself or loaded wholesale from an external properties file or an external resource.
...
The property is not declared in the configuration file, thus logback will look for it in the System properties.

Logback can use system properties or properties defined explicitely. So you need to tell logback to use application.properties file

<property resource="application.properties" />