如何在tomcat9上使用log4j2

Question

I am using log4j2 to print log to a file. It work when I use it on my own computer, but when I deploying war on tomcat, It didn't work. And I have wasted a whole day on this.
My tomcat version:

Server version: Apache Tomcat/9.0.62
Server built:   Mar 31 2022 14:34:15 UTC
Server number:  9.0.62.0
OS Name:        Linux
OS Version:     4.15.0-161-generic
Architecture:   amd64
JVM Version:    17.0.2+8-Ubuntu-118.04
JVM Vendor:     Private Build

My log4j2.xml:

<Configuration xmlns="http://logging.apache.org/log4j/2.0/config" strict="true" status="ERROR" name="ConfigTest">
    <Properties>
        <Property name="FILE_NAME">./src/logs/myLog.log</Property>
    </Properties>
    <Appenders>
<!--        log to file-->
        <Appender type="File" name="File" fileName="${FILE_NAME}">
            <Layout type="PatternLayout">
                <Pattern>%d %p %C{1.} [%t] %m%n</Pattern>
            </Layout>
        </Appender>
<!--        log to console-->
        <Appender type="Console" name="STDOUT">
            <Layout type="PatternLayout" pattern="%d %p %C{1.} [%t] %m%n"/>
            <Filters>
                <Filter type="MarkerFilter" marker="FLOW" onMatch="DENY" onMismatch="NEUTRAL"/>
                <Filter type="MarkerFilter" marker="EXCEPTION" onMatch="DENY" onMismatch="ACCEPT"/>
            </Filters>
        </Appender>
    </Appenders>

    <Loggers>
        <Root level="info">
            <AppenderRef ref="File"/>
        </Root>
    </Loggers>
</Configuration>

And I use log4j2 like this:

@SpringBootApplication
public class DemoApplication extends ServletInitializer { //

    private static final Logger shortMessageLogger = LogManager.getLogger("shortMessageLogger");
    public static void main(String[] args) {
        shortMessageLogger.error("start running...");
        SpringApplication.run(DemoApplication.class, args);
    }
}

And my application.properies:

logging.config=classpath:log4j2.xml

And my maven pom.xml like this:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.6.6</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>war</packaging>
    <name>demo</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>17</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>

            <!-- exclusion embedded loggin -->
            <exclusions>
                <exclusion>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-starter-logging</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.2.2</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <!-- log4j2 -->
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-api</artifactId>
            <version>2.17.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-core</artifactId>
            <version>2.17.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-appserver</artifactId>
            <version>2.17.2</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>

        <finalName>Demo</finalName>
    </build>
</project>

I found maybe it's because the tomcat9 has its own logger configuration and covered my config. I also referred to theApache log4j2 documentation , but failed because it was not specific enough. So where I could get the more detailed process?

Answer 1

Tomcat by default uses java.util.logging as its logging backend, so it does not interfere with your application logging.

The most probable reason for your lack of logs is a permission problem, when creating the file ./src/logs/myLog.log . The error should be logged by Log4j's status logger (on stdout , which usually ends up in catalina.out ).

When you run a Tomcat server, you can never assume anything about the working directory of the server, so you should not use relative paths. A more safe location for your log file is ${sys:catalina.base}/logs/myLog.log , since Tomcat can write to that directory.