How can I read properties from spring application.yml and use it in my log4j2.xml

Question

I have properties defined in application.yml and wanted to use them in my log4j2.xml file.

**application.properties**

logging:
  levels:
    com.mypackage: INFO
  appenders:
    name: rollingfile

I tried below approach but didn't work

    <Properties>
        <Property name="log-pattern">%d{ISO8601} %-5level {%thread} [%-40.40logger{39}] request_id=%X{requestId} %m%n</Property>
        <Property name="logging-level">${bundle:application:logging.levels.com.mypackage}</Property>
    </Properties>

<Loggers>       
        <Logger name="com.service" level="${logging-level}" includeLocation="true" additivity="false">
            <AppenderRef ref="${logging.appenders.name}"/>
        </Logger>
<Loggers>

Please help me out in resolving to read value.I am not able to get any working solution.

Answer 1

If you are using Spring Boot you can use Log4j's Spring Cloud Config Client jar which provides the Spring Lookup. Then you can code:

    <Properties>
        <Property name="log-pattern">%d{ISO8601} %-5level {%thread} [%-40.40logger{39}] request_id=%X{requestId} %m%n</Property>
        <Property name="logging-level">${spring:logging.levels.com.mypackage}</Property>
    </Properties>
    <Loggers>       
        <Logger name="com.service" level="${logging-level}" includeLocation="true" additivity="false">
            <AppenderRef ref="${spring:logging.appenders.name}"/>
        </Logger>
    <Loggers>

However, the Spring lookup will only work after Spring has initialized its environment. Spring Boot initializes logging at least 3 times and the first is prior to Spring doing anything. For that case you either need to provide default values or a different configuration just for the initial startup.