SLF4J Filter Log Messages By Markers

Question

I use Spring Boot and Slf4j at my application. I need to log specific audit events. Auditing with JPA, Hibernate, or Spring Data JPA does not fit with my needs since I want to log service level audit instead of DB. So, I decided to use Markers with loggers and then persist them into DB.

However, how can I interrupt all log messages and filter the ones which has my audit markers? All in all, they should be logged into a file too as like the ones without markers.

Answer 1

Database Appender

Spring uses Logback as the underlying log framework.

You can create a logback-spring.xml file in src/resources and then configure your logger. There is the default FILE appender and you can add your DATABASE appender

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <include resource="org/springframework/boot/logging/logback/base.xml"/>

    <springProperty name="spring.datasource.driverClassName" source="spring.datasource.driverClassName"/>
    <springProperty name="spring.datasource.url" source="spring.datasource.url"/>
    <springProperty name="spring.datasource.username" source="spring.datasource.username"/>
    <springProperty name="spring.datasource.password" source="spring.datasource.password"/>

    <appender name="DATABASE" class="ch.qos.logback.classic.db.DBAppender">
        <connectionSource class="ch.qos.logback.core.db.DriverManagerConnectionSource">
            <driverClass>${spring.datasource.driverClassName}</driverClass>
            <url>${spring.datasource.url}</url>
            <user>${spring.datasource.username}</user>
            <password>${spring.datasource.password}</password>
        </connectionSource>
    </appender>

    <logger name="AUDIT" level="INFO">
        <appender-ref ref="FILE"/>
        <appender-ref ref="DATABASE"/>
    </logger>
 </configuration>

Additional Information

You can use the mapped diagnostic context (MDC) to store global information that you want to add to every log entry:

MDC.put("username", SecurityContextHolder.getContext().getAuthentication().getName());

To have it in the output you have to add it to the log pattern. For example:

<Pattern>%X{username} - %m%n</Pattern>

Further reading

I recommend to read the logback manual to get more information about appenders and MDC:

https://logback.qos.ch/manual/mdc.html