sl4j的多种log4j实现导致日志不能打印

最新推荐文章于 2025-02-07 17:57:47 发布

原创最新推荐文章于 2025-02-07 17:57:47 发布 · 3.4k 阅读

2 ·

CC 4.0 BY-SA版权

文章标签：

#log4j2

Java 专栏收录该内容

87 篇文章

订阅专栏

本文介绍了一个因日志jar冲突导致项目日志无法打印的问题及解决方法。通过分析pom文件和日志输出，找到了冲突源头并成功排除。同时讨论了隐式依赖带来的问题。

前言

目前在做项目过程中，发现部分项目的日志无法打印，一直不知道原因。分析发现是日志jar冲突，由于日志jar冲突是隐式引用，很难排查，加上我们经常不注意日志本身的报错。

1. 冲突jar

模拟jar冲突的project，pom如下

<dependencies>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>1.6.1</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-slf4j-impl</artifactId>
            <version>2.10.0</version>
        </dependency>


        <!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-api -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.26</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-api -->
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-api</artifactId>
            <version>2.10.0</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-core -->
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-core</artifactId>
            <version>2.10.0</version>
        </dependency>

    </dependencies>

随意写一个log4j2.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="info">
    <Appenders>
        <Console name="console" target="SYSTEM_OUT">
            <PatternLayout pattern="%d{DATE} %c{1}:%L - %m%n" />
        </Console>
    </Appenders>
    <Loggers>
        <Root level="info">
            <AppenderRef ref="console" />
        </Root>
    </Loggers>
</Configuration>

写一个测试方法，这里说一下sl4j是日志接口，没有实现，可以集成log4j2与logback等，推荐使用打日志。

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class Slf4jDemo {
    private static final Logger logger = LoggerFactory.getLogger(Slf4jDemo.class);

    public static void main(String[] args) {
        logger.info("----------------------------");
    }
}

运行结果如下：

/software/jdk1.8.0_191/bin/java -javaagent:/software/ideaIde/lib/idea_rt.jar=36051:/software/ideaIde/bin -Dfile.encoding=UTF-8 -classpath /software/jdk1.8.0_191/jre/lib/charsets.jar:/software/jdk1.8.0_191/jre/lib/deploy.jar:/software/jdk1.8.0_191/jre/lib/ext/cldrdata.jar:/software/jdk1.8.0_191/jre/lib/ext/dnsns.jar:/software/jdk1.8.0_191/jre/lib/ext/jaccess.jar:/software/jdk1.8.0_191/jre/lib/ext/jfxrt.jar:/software/jdk1.8.0_191/jre/lib/ext/localedata.jar:/software/jdk1.8.0_191/jre/lib/ext/nashorn.jar:/software/jdk1.8.0_191/jre/lib/ext/sunec.jar:/software/jdk1.8.0_191/jre/lib/ext/sunjce_provider.jar:/software/jdk1.8.0_191/jre/lib/ext/sunpkcs11.jar:/software/jdk1.8.0_191/jre/lib/ext/zipfs.jar:/software/jdk1.8.0_191/jre/lib/javaws.jar:/software/jdk1.8.0_191/jre/lib/jce.jar:/software/jdk1.8.0_191/jre/lib/jfr.jar:/software/jdk1.8.0_191/jre/lib/jfxswt.jar:/software/jdk1.8.0_191/jre/lib/jsse.jar:/software/jdk1.8.0_191/jre/lib/management-agent.jar:/software/jdk1.8.0_191/jre/lib/plugin.jar:/software/jdk1.8.0_191/jre/lib/resources.jar:/software/jdk1.8.0_191/jre/lib/rt.jar:/home/huahua/IdeaProjects/demo/target/classes:/home/huahua/.m2/repository/org/slf4j/slf4j-log4j12/1.6.1/slf4j-log4j12-1.6.1.jar:/home/huahua/.m2/repository/log4j/log4j/1.2.16/log4j-1.2.16.jar:/home/huahua/.m2/repository/org/apache/logging/log4j/log4j-slf4j-impl/2.10.0/log4j-slf4j-impl-2.10.0.jar:/home/huahua/.m2/repository/org/slf4j/slf4j-api/1.7.26/slf4j-api-1.7.26.jar:/home/huahua/.m2/repository/org/apache/logging/log4j/log4j-api/2.10.0/log4j-api-2.10.0.jar:/home/huahua/.m2/repository/org/apache/logging/log4j/log4j-core/2.10.0/log4j-core-2.10.0.jar com.feng.demo.Slf4jDemo
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/home/huahua/.m2/repository/org/slf4j/slf4j-log4j12/1.6.1/slf4j-log4j12-1.6.1.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/home/huahua/.m2/repository/org/apache/logging/log4j/log4j-slf4j-impl/2.10.0/log4j-slf4j-impl-2.10.0.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.slf4j.impl.Log4jLoggerFactory]
log4j:WARN No appenders could be found for logger (com.feng.demo.Slf4jDemo).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.

Process finished with exit code 0

由于经常忽略wran日志，项目启动后仅有少量的业务日志（估计有些日志不是log4j实现的），所以很难排查问题。

其实上面的日志已经说明了冲突的地方

SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/home/huahua/.m2/repository/org/slf4j/slf4j-log4j12/1.6.1/slf4j-log4j12-1.6.1.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/home/huahua/.m2/repository/org/apache/logging/log4j/log4j-slf4j-impl/2.10.0/log4j-slf4j-impl-2.10.0.jar!/org/slf4j/impl/StaticLoggerBinder.class]

org/slf4j/impl/StaticLoggerBinder.class在2个jar

slf4j-log4j12-1.6.1.jar

log4j-slf4j-impl-2.10.0.jar

都有实现，由于使用的log4j2，slf4j-log4j12-1.6.1.jar是log4j的1.x版本用的，只有删除依赖就可以了。

删除后日志正常

30 三月 2019 10:23:55,282 Slf4jDemo:10 - ----------------------------

2. 隐式依赖冲突

我们知道使用log4j2不会引用log4j的1.x的版本，那么上面的依赖怎么来的呢，这里就是隐式依赖造成的

笔者是使用zookeeper的jar没注意引入的，比如zookeeper的3.4.13的jar

<!-- https://mvnrepository.com/artifact/org.apache.zookeeper/zookeeper -->
<dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.4.13</version>
    <type>pom</type>
</dependency>

在mvnrepository.com中明确说明依赖log4j的1.x的jar