logback externalization

Question

Currently I have logback configuration file i.e logback.xml which is src/main/resources. I want to set the logging level but i want control outside of war.

One solution which i could think of is to externalize it in properties file, load it on server startup and substitute the placeholder. Is there any better way of doing it ? Can't we keep logback.xml outside of war file ?

    <configuration>
    <appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>${catalina.base}/logs/logFile.log</file>
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <!-- daily rollover -->
            <fileNamePattern>logFile.%d{yyyy-MM-dd}.log</fileNamePattern>
            <!-- keep 7 days' worth of history -->
            <maxHistory>7</maxHistory>
        </rollingPolicy>
        <encoder>
            <pattern>%date [%thread] %-5level %logger{35} - %msg%n</pattern>
        </encoder>
    </appender>
    
    <root level="DEBUG">
        <appender-ref ref="FILE"/>
    </root>
</configuration>

Answer 1

If you just want to change the log level you don't need to override the whole file, you can do this:

<root level="${log.level:-INFO}">

Then if you set the system property:

-Dlog.level=DEBUG

It will override the default of 'INFO'.

Answer 2

I suggest you use 2 logback configuration files. The first one in the classpath defined as:

<configuration scan="true">
    <property file="/otherfolder/project.properties" />
    <include file="/otherfolder/logback.xml"/>
</configuration>

and you put all the configuration in the other one. Logback will scan both files for updates.