使用Tinkerpop3 Gremlin的GraphTraversalSource时如何解决Log4j2警告

使用Tinkerpop-3的Gremlin语言和GraphTraversalSource时，如何修复Log4j2的警告？

代码文件 src/main/java/Main.java #

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.apache.tinkerpop.gremlin.process.traversal.dsl.graph.GraphTraversalSource;

import static org.apache.tinkerpop.gremlin.process.traversal.AnonymousTraversalSource.traversal;

public class Main {
    private static final Logger logger = LogManager.getLogger(Main.class);
    public static void main(String[] args) throws Exception {
        System.out.println("Hello world!");
        logger.info("Hello world!");
        GraphTraversalSource g = traversal().withRemote("conf/remote-graph.properties");
    }
}

日志配置文件 src/main/resources/log4j2.xml #

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn" name="MyApp">
    <Properties>
        <Property name="baseDir">logs</Property>
    </Properties>
    <Appenders>
        <RollingFile name="RollingFile" fileName="${baseDir}/${date:yyyy-MM-dd}/log-${date:yyyy-MM-dd}.log"
                     filePattern="logs/${date:yyyy-MM}/app-%d{yyyy-MM-dd-HH}-%i.log.gz">
            <PatternLayout>
                <Pattern>%d [%p] [%c{1.}.%t] ::&#x09; %m%n</Pattern>
            </PatternLayout>
            <Policies>
                <TimeBasedTriggeringPolicy interval="6" modulate="true"/>
                <SizeBasedTriggeringPolicy size="250 MB"/>
            </Policies>
        </RollingFile>
        <Console name="STDOUT" target="SYSTEM_OUT">
            <PatternLayout>
                <Pattern>%d [%p] [%c{1.}.%t] ::&#x09; %m%n</Pattern>
            </PatternLayout>
        </Console>
    </Appenders>
    <Loggers>
        <Root level="debug">
            <AppenderRef ref="STDOUT"/>
            <AppenderRef ref="RollingFile"/>
        </Root>
    </Loggers>
</Configuration>

Maven依赖 pom.xml #

<dependencies>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-core</artifactId>
        <version>2.20.0</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-api</artifactId>
        <version>2.20.0</version>
    </dependency>
    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-log4j12</artifactId>
        <version>1.7.5</version>
    </dependency>
</dependencies>

注释掉GraphTraversalSource相关代码时程序正常运行；取消注释后，Log4j2日志能正常输出"Hello world!"，和System.out的输出一致。
该代码是从使用OrientGraph的OrientDB环境中复制而来：

OrientGraph orientGraph = OrientGraph.open(configuration);
GraphTraversalSource g = orientGraph.traversal();

Hello world!
2023-04-28 09:14:06,725 [INFO] [Main.main] ::    Hello world!
log4j:WARN No appenders could be found for logger (org.apache.commons.beanutils.converters.BooleanConverter).
log4j:WARN Please initialize the log4j system properly.

警告的核心原因是依赖中混用了Log4j 1.x和2.x的桥接包，加上Tinkerpop依赖的组件（比如Apache Commons BeanUtils）仍在使用Log4j 1.x API，导致日志系统加载混乱，具体修复步骤如下：

1. 替换错误的SLF4J桥接包
   移除slf4j-log4j12，换成Log4j 2.x官方的SLF4J桥接包log4j-slf4j-impl，同时添加Log4j 1.x到2.x的兼容桥接包，让依赖Log4j 1.x的组件也能通过Log4j2输出日志：

   <dependencies>
       <dependency>
           <groupId>org.apache.logging.log4j</groupId>
           <artifactId>log4j-core</artifactId>
           <version>2.20.0</version>
       </dependency>
       <dependency>
           <groupId>org.apache.logging.log4j</groupId>
           <artifactId>log4j-api</artifactId>
           <version>2.20.0</version>
       </dependency>
       <!-- 替换原slf4j-log4j12 -->
       <dependency>
           <groupId>org.apache.logging.log4j</groupId>
           <artifactId>log4j-slf4j-impl</artifactId>
           <version>2.20.0</version>
       </dependency>
       <!-- 兼容Log4j 1.x的组件 -->
       <dependency>
           <groupId>org.apache.logging.log4j</groupId>
           <artifactId>log4j-1.2-api</artifactId>
           <version>2.20.0</version>
       </dependency>
   </dependencies>
   

2. 修正配置文件路径
   确保log4j2.xml放在src/main/resources目录下（你当前的路径src/java/main/resources不符合Maven规范），这样程序启动时能正确加载配置。

3. 清理依赖冲突
   执行mvn dependency:tree检查依赖树，若发现存在Log4j 1.x的log4j artifact，通过<exclusions>在对应的Tinkerpop依赖中排除：

   <!-- 示例：排除Gremlin驱动中的Log4j 1.x依赖 -->
   <dependency>
       <groupId>org.apache.tinkerpop</groupId>
       <artifactId>gremlin-driver</artifactId>
       <version>你的版本号</version>
       <exclusions>
           <exclusion>
               <groupId>log4j</groupId>
               <artifactId>log4j</artifactId>
           </exclusion>
       </exclusions>
   </dependency>
   

完成以上操作后重新运行程序，Log4j2的警告会消除，所有日志将按照你配置的log4j2.xml规则输出。

内容的提问来源于stack exchange，提问作者Zach