Log4j Spring Boot Support

Spring Lookup

The Spring Lookup allows configuration files to reference properties defined in Spring configuration files from a Log4j configuration file. For example:

<property name="applicationName">${spring:spring.application.name}</property>

would set the Log4j applicationName property to the value of spring.application.name set in the Spring configuration.

Spring Property Source

Log4j uses property sources when resolving properties it uses internally. This support allows most of Log4j's System Properties to be specified in the Spring Configuration. However, some properties that are only referenced during the first Log4j initialization, such as the property Log4j uses to allow the default Log4j implementation to be chosen, would not be available.

Spring Profile Arbiter

New with Log4j 2.15.0 are “Arbiters” which are conditionals that can cause a portion of the Log4j configuration to be included or excluded. log4j-spring-boot provides an Arbiter that allows a Spring profile value to be used for this purpose. Below is an example:

<Configuration name="ConfigTest" status="ERROR" monitorInterval="5">
  <Appenders>

    <SpringProfile name="dev | staging">
      <Console name="Out">
        <PatternLayout pattern="%m%n"/>
      </Console>
    </SpringProfile>
    <SpringProfile name="prod">
      <List name="Out">
      </List>
    </SpringProfile>

  </Appenders>
  <Loggers>
    <Logger name="org.apache.test" level="trace" additivity="false">
      <AppenderRef ref="Out"/>
    </Logger>
    <Root level="error">
      <AppenderRef ref="Out"/>
    </Root>
  </Loggers>
</Configuration>