How to have Spring boot use a log4j.xml configuration file?

Question

I have a simple Spring Boot application that builds to a jar file. I have a log4j.xml file in src/main/resources/log4j.xml that looks like this (basic sample file from the log4j docs):

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
    <appender name="stdout" class="org.apache.log4j.ConsoleAppender">
        <layout class="org.apache.log4j.PatternLayout">
            <!-- Pattern to output the caller's file name and line number -->
            <param name="ConversionPattern" value="%5p [%t] (%F:%L) - %m%n"/>
        </layout>
    </appender>
    <appender name="R" class="org.apache.log4j.RollingFileAppender">
        <param name="file" value="/tmp/logs/sample.log"/>
        <param name="MaxFileSize" value="100KB"/>
        <!-- Keep one backup file -->
        <param name="MaxBackupIndex" value="1"/>
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%p %t %c - %m%n"/>
        </layout>
    </appender>
    <root>
        <priority value="debug"/>
        <appender-ref ref="stdout"/>
        <appender-ref ref="R"/>
    </root>
</log4j:configuration>

Logging only goes to the console though (/tmp/logs/sample.log never gets created), as it the log4j.xml file is being ignored.

The file shows up in the root of the jar, which I assume is correct. What else do I need to do to have this logging configuration picked up?

If it makes any difference, the project is using Gradle, not Maven.

Answer 1

It depends how you set up your classpath. Is the log4j binding to slf4j on your classpath (it won't be if you just use the vanilla spring-boot-starter)? The is a spring-boot-starter-log4j and a sample showing how to use it (in Maven, but Gradle has the same features).

If I were you I'd just use logback.

N.B. Spring Boot 1.4 does not support log4j (only log4j2). There's a sample for that in the same place though.