Caused by: org.apache.logging.log4j.LoggingException: log4j-slf4j-impl cannot be present with log4j-to-slf4j

Question

In my Spring boot 2 project:

In build.gradle :

dependencies {
    implementation 'com.google.code.gson:gson:2.7'
    implementation 'com.h2database:h2'
    implementation 'javax.servlet:jstl:1.2'
    implementation 'org.springframework.boot:spring-boot-devtools'
    implementation('org.springframework.boot:spring-boot-starter') {
        exclude group: 'org.springframework.boot', module: 'spring-boot-starter-logging'
    }
    implementation 'org.springframework.boot:spring-boot-starter-actuator'
    implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
    implementation 'org.springframework.boot:spring-boot-starter-log4j2'
    implementation 'org.springframework.boot:spring-boot-starter-jdbc'
    implementation 'org.springframework.boot:spring-boot-starter-security'
    implementation 'org.springframework.boot:spring-boot-starter-thymeleaf'
    implementation "org.springframework.boot:spring-boot-starter-web"

    testImplementation('org.springframework.boot:spring-boot-starter-test') {
        exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
    }

    testImplementation 'org.junit.jupiter:junit-jupiter:5.5.2'
}

In src/resources/log4j2.xml :

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">

<log4j:configuration debug="true" xmlns:log4j="http://jakarta.apache.org/log4j/">

    <appender name="Console"
              class="org.apache.log4j.ConsoleAppender">
        <layout class="org.apache.log4j.PatternLayout">
            <!-- l, L, M - is extremely slow. It's use should be avoided unless execution
                speed is not an issue. -->
            <param name="ConversionPattern"
                   value="%p: %d{dd.MM.yyyy HH:mm:ss.SSS} %l %n    %m%n"/>
        </layout>
    </appender>

    <appender name="File"
              class="org.apache.log4j.DailyRollingFileAppender">
        <param name="Encoding" value="UTF-8"/>
        <param name="File" value="logs/trace.log"/>
        <param name="Append" value="true"/>
        <layout class="org.apache.log4j.PatternLayout">
            <!-- l, L, M - is extremely slow. It's use should be avoided unless execution
                speed is not an issue. -->
            <param name="ConversionPattern"
                   value="%p: %d{dd.MM.yyyy HH:mm:ss.SSS} %l %n    %m%n"/>
        </layout>
    </appender>

    <!-- Application Loggers -->
    <logger name="com.journaldev.spring">
        <level value="info"/>
    </logger>

    <!-- 3rdparty Loggers -->
    <logger name="org.springframework.core">
        <level value="info"/>
    </logger>

    <logger name="org.hibernate">
        <level value="info"/>
    </logger>

    <logger name="org.springframework.beans">
        <level value="info"/>
    </logger>

    <logger name="org.springframework.context">
        <level value="info"/>
    </logger>

    <logger name="org.springframework.web">
        <level value="info"/>
    </logger>

    <!-- The root category is used for all loggers unless a more specific logger
        matches. If none of the loggers are assigned a level, then all loggers inherit
        the level of the root logger which is set to DEBUG by default -->
    <root>
        <level value="ALL"/>
        <appender-ref ref="Console"/>
        <!-- <appender-ref ref="File" /> -->
    </root>

</log4j:configuration>

In my controller:

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;

@Controller
public class CategoryController {
    private CategoryRepository categoryRepository;

    private static Logger logger = LoggerFactory.getLogger(CategoryController.class);

 @GetMapping("/categories")
    public String getCategories(Model model) {
        logger.debug("getCategories>>>>>>>>>>>>>>>>");
        model.addAttribute("categoryList", this.categoryRepository.findAll());
        return "categories/category_list";
    }
}

But when I start project I get error:

Caused by: org.apache.logging.log4j.LoggingException: log4j-slf4j-impl cannot be present with log4j-to-slf4j

Answer 1

According with Spring's documentation (as pointed by Simon), we wave to exclude the "spring-boot-starter-logging" module from all libraries , not only from "spring-boot-starter-web".

configurations {
    ...
    all {
        exclude group: 'org.springframework.boot', module: 'spring-boot-starter-logging'
    }
}

...instead of...

dependencies {
    ...
    implementation('org.springframework.boot:spring-boot-starter') {
        exclude group: 'org.springframework.boot', module: 'spring-boot-starter-logging'
    }
}

Just had myself the same problem and solved with this solution.

Answer 2

Spring boot 2.3.0.RELEASE version, support Log4j2 natively, for logging configuration if it is on the classpath. In this case, you can simply remove other log4j dependencies.

In other case, if you use the starters for assembling dependencies, you have to exclude Logback and then include log4j 2 instead:

You can do like that with Gradle :

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-web'
    implementation 'org.springframework.boot:spring-boot-starter-log4j2'
}

configurations {
    all {
        exclude group: 'org.springframework.boot', module: 'spring-boot-starter-logging'
    }
}

Or with Maven :

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter</artifactId>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-logging</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-log4j2</artifactId>
</dependency>

More information on the official documentation: https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#howto-configure-log4j-for-logging

Answer 3

I excluded spring boot logging from build.gradle but issue was still occurring. It got resolved by removing org.apache.logging.log4j/log4j-slf4j-impl/2.12.1 from .classpath

Answer 4

From the error logs decide which project to exclude.

eg for a error msg like this: Caused by: org.apache.logging.log4j.LoggingException: log4j-slf4j-impl cannot be present with log4j-to-slf4j I've used the gradle exclude:

configurations.all { exclude group: 'org.apache.logging.log4j'

}

Answer 5

即使在更正类路径之后，我在 STS 中也遇到了同样的问题，Gradle 'Refresh All' 解决了它。

Answer 6

解决此问题的最佳方法是运行 gradle 依赖项，并确定 log4j-to-slf4j 的来源，然后在 build.gradle 中排除此模块