Log4j2无法读取自定义配置文件，始终使用默认配置求助

问题描述 #

尝试让Log4j2打印debug日志，无论怎么操作（包括命令行指定配置文件）都只使用默认配置。运行mvn clean test -Dlog4j.debug时出现以下警告：

WARN StatusLogger Multiple logging implementations found:
Factory: org.apache.logging.log4j.core.impl.Log4jContextFactory, Weighting: 10
Factory: org.apache.logging.slf4j.SLF4JLoggerContextFactory, Weighting: 15
Using factory: org.apache.logging.slf4j.SLF4JLoggerContextFactory

项目包含Playwright、Spring Boot等依赖，不确定是否影响。

相关代码与配置 #

Java代码

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

class ExampleClass {
    static Logger logger = LogManager.getLogger();

    void main() {
        logger.debug("Hello world")
    }
}

Log4j2配置文件（src/main/resources/log4j2.xml）

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="trace">
    <Appenders>
        <Console name="Console" target="SYSTEM_OUT">
            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
        </Console>
    </Appenders>
    <Loggers>
        <Root level="all">
            <AppenderRef ref="Console"/>
        </Root>
    </Loggers>
</Configuration>

pom.xml核心依赖片段

<!-- Spring data JPA -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
    <version>3.2.0</version>
</dependency>

<!-- Spring boot web -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <version>3.2.0</version>
</dependency>

<!-- Log4j -->
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-api</artifactId>
    <version>2.17.1</version>
</dependency>
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-core</artifactId>
    <version>2.17.1</version>
</dependency>

问题原因 #

1. SLF4J上下文工厂抢占：警告明确显示系统选择了SLF4JLoggerContextFactory而非Log4j2原生工厂，说明类路径中存在SLF4J与Log4j2的桥接冲突，导致Log4j2的配置被忽略。
2. Spring Boot默认日志干扰：Spring Boot Starter依赖（如spring-boot-starter-web、spring-boot-starter-data-jpa）默认引入spring-boot-starter-logging，该依赖使用SLF4J+Logback作为默认日志实现，会覆盖Log4j2的配置。
3. 依赖传递冲突：Playwright等第三方依赖可能也引入了SLF4J相关实现，进一步加剧冲突。

解决步骤 #

1. 排除Spring Boot默认日志依赖 #

在所有Spring Boot Starter依赖中排除spring-boot-starter-logging，避免Logback干扰：

<!-- Spring data JPA -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
    <version>3.2.0</version>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-logging</artifactId>
        </exclusion>
    </exclusions>
</dependency>

<!-- Spring boot web -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <version>3.2.0</version>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-logging</artifactId>
        </exclusion>
    </exclusions>
</dependency>

<!-- Spring boot test -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-test</artifactId>
    <version>3.2.0</version>
    <scope>test</scope>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-logging</artifactId>
        </exclusion>
    </exclusions>
</dependency>

2. 引入Spring Boot适配的Log4j2 Starter #

替换原生Log4j2依赖为Spring Boot官方适配版本，自动处理依赖桥接与版本管理：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-log4j2</artifactId>
    <version>3.2.0</version>
</dependency>

注：添加此依赖后，可移除单独引入的log4j-api和log4j-core，因为Starter已包含并管理这两个依赖。

3. 排查并排除其他SLF4J冲突 #

运行mvn dependency:tree查看依赖树，找出其他引入SLF4J实现的依赖（如Playwright），排除对应的冲突依赖：

<!-- Playwright -->
<dependency>
    <groupId>com.microsoft.playwright</groupId>
    <artifactId>playwright</artifactId>
    <version>1.39.0</version>
    <exclusions>
        <exclusion>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-simple</artifactId>
        </exclusion>
    </exclusions>
</dependency>

4. 验证配置生效 #

重新运行项目或执行mvn clean test -Dlog4j.debug，若看到以下日志，说明Log4j2配置已生效：

INFO StatusLogger Log4j2 version 2.20.0 initialized from classpath resource [log4j2.xml]

5. 修复代码语法问题 #

Java入口方法需定义为public static void main(String[] args)，且语句末尾需加分号：

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

class ExampleClass {
    static Logger logger = LogManager.getLogger();

    public static void main(String[] args) {
        logger.debug("Hello world");
    }
}

内容的提问来源于stack exchange，提问作者gbiz123