Grouping Appenders At Logback?

Question

I have two appenders. One of them is DB appender and the other one is SMTPAppender. When I log a string with a special marker I want to use both my custom db appender and SMTPAppender. However I don't want to define two appenders everythime as like that:

<logger name="com.MyClass" level="DEBUG" additivity="false">
    <appender-ref ref="CUSTOM_DB"/>
    <appender-ref ref="CUSTOM_EMAIL"/>
</logger>

I want a special reference that as like that:

<appender-group ref="CUSTOM_COMBO">
    <appender-ref ref="CUSTOM_DB"/>
    <appender-ref ref="CUSTOM_EMAIL"/>
</appender-group>

<logger name="com.MyClass" level="DEBUG" additivity="false">
    <appender-ref ref="CUSTOM_COMBO"/>
</logger>

It should both call CUSTOM_DB and CUSTOM_EMAIL. How can I do that at Logback with slf4j?

Answer 1

So from https://tersesystems.com/blog/2019/05/27/application-logging-in-java-part-5/

public class CompositeAppender<E> extends UnsynchronizedAppenderBase<E> implements AppenderAttachable<E> {

    protected AppenderAttachableImpl<E> aai = new AppenderAttachableImpl<E>();

    @Override
    protected void append(E eventObject) {
        aai.appendLoopOnAppenders(eventObject);
    }

    // AppenderAttachable API delegates to aai in all cases
}

and

<configuration>

    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>[%-5level] %logger{15} -  message%n%xException{10}</pattern>
        </encoder>
    </appender>

    <appender name="FILE" class="ch.qos.logback.core.FileAppender">
        <file>file.log</file>
        <encoder>
            <pattern>%date - %message</pattern>
        </encoder>
    </appender>

    <appender name="CONSOLE_AND_FILE" class="com.tersesystems.logback.CompositeAppender">
        <appender-ref ref="CONSOLE"/>
        <appender-ref ref="FILE"/>
    </appender>

    <root level="TRACE">
        <appender-ref ref="CONSOLE_AND_FILE"/>
    </root>
</configuration>