log4j和log4j-extras中的重复类？

Question

为什么在log4j 1.2.17和log4j-extras-1.2.17中存在重复的类，这是否是错误？这使我很烦恼，警告是在启动码头服务器时从多个罐中扫描了这些类。

[WARNING] org.apache.log4j.Appender scanned from multiple locations: jar:file:///home/ggfan/.m2/repository/log4j/apache-log4j-extras/1.2.17/apache-log4j-extras-1.2.17.jar!/org/apache/log4j/Appender.class, jar:file:///home/ggfan/.m2/repository/log4j/log4j/1.2.17/log4j-1.2.17.jar!/org/apache/log4j/Appender.class
[WARNING] org.apache.log4j.AppenderSkeleton scanned from multiple locations: jar:file:///home/ggfan/.m2/repository/log4j/apache-log4j-extras/1.2.17/apache-log4j-extras-1.2.17.jar!/org/apache/log4j/AppenderSkeleton.class, jar:file:///home/ggfan/.m2/repository/log4j/log4j/1.2.17/log4j-1.2.17.jar!/org/apache/log4j/AppenderSkeleton.class
[WARNING] org.apache.log4j.AsyncAppender$DiscardSummary scanned from multiple locations: jar:file:///home/ggfan/.m2/repository/log4j/apache-log4j-extras/1.2.17/apache-log4j-extras-1.2.17.jar!/org/apache/log4j/AsyncAppender$DiscardSummary.class, jar:file:///home/ggfan/.m2/repository/log4j/log4j/1.2.17/log4j-1.2.17.jar!/org/apache/log4j/AsyncAppender$DiscardSummary.class
[WARNING] org.apache.log4j.AsyncAppender$Dispatcher scanned from multiple locations: jar:file:///home/ggfan/.m2/repository/log4j/apache-log4j-extras/1.2.17/apache-log4j-extras-1.2.17.jar!/org/apache/log4j/AsyncAppender$Dispatcher.class, jar:file:///home/ggfan/.m2/repository/log4j/log4j/1.2.17/log4j-1.2.17.jar!/org/apache/log4j/AsyncAppender$Dispatcher.class
[WARNING] org.apache.log4j.AsyncAppender scanned from multiple locations: jar:file:///home/ggfan/.m2/repository/log4j/apache-log4j-extras/1.2.17/apache-log4j-extras-1.2.17.jar!/org/apache/log4j/AsyncAppender.class, jar:file:///home/ggfan/.m2/repository/log4j/log4j/1.2.17/log4j-1.2.17.jar!/org/apache/log4j/AsyncAppender.class
[WARNING] org.apache.log4j.BasicConfigurator scanned from multiple locations: jar:file:///home/ggfan/.m2/repository/log4j/apache-log4j-extras/1.2.17/apache-log4j-extras-1.2.17.jar!/org/apache/log4j/BasicConfigurator.class, jar:file:///home/ggfan/.m2/repository/log4j/log4j/1.2.17/log4j-1.2.17.jar!/org/apache/log4j/BasicConfigurator.class
[WARNING] org.apache.log4j.Category scanned from multiple locations: jar:file:///home/ggfan/.m2/repository/log4j/apache-log4j-extras/1.2.17/apache-log4j-extras-1.2.17.jar!/org/apache/log4j/Category.class, jar:file:///home/ggfan/.m2/repository/log4j/log4j/1.2.17/log4j-1.2.17.jar!/org/apache/log4j/Category.class
[WARNING] org.apache.log4j.CategoryKey scanned from multiple locations: jar:file:///home/ggfan/.m2/repository/log4j/apache-log4j-extras/1.2.17/apache-log4j-extras-1.2.17.jar!/org/apache/log4j/CategoryKey.class, jar:file:///home/ggfan/.m2/repository/log4j/log4j/1.2.17/log4j-1.2.17.jar!/org/apache/log4j/CategoryKey.class
[WARNING] org.apache.log4j.ConsoleAppender$SystemErrStream scanned from multiple locations: jar:file:///home/ggfan/.m2/repository/log4j/apache-log4j-extras/1.2.17/apache-log4j-extras-1.2.17.jar!/org/apache/log4j/ConsoleAppender$SystemErrStream.class, jar:file:///home/ggfan/.m2/repository/log4j/log4j/1.2.17/log4j-1.2.17.jar!/org/apache/log4j/ConsoleAppender$SystemErrStream.class
[WARNING] org.apache.log4j.ConsoleAppender$SystemOutStream scanned from multiple locations: jar:file:///home/ggfan/.m2/repository/log4j/apache-log4j-extras/1.2.17/apache-log4j-extras-1.2.17.jar!/org/apache/log4j/ConsoleAppender$SystemOutStream.class, jar:file:///home/ggfan/.m2/repository/log4j/log4j/1.2.17/log4j-1.2.17.jar!/org/apache/log4j/ConsoleAppender$SystemOutStream.class
[WARNING] org.apache.log4j.ConsoleAppender scanned from multiple locations: jar:file:///home/ggfan/.m2/repository/log4j/apache-log4j-extras/1.2.17/apache-log4j-extras-1.2.17.jar!/org/apache/log4j/ConsoleAppender.class, jar:file:///home/ggfan/.m2/repository/log4j/log4j/1.2.17/log4j-1.2.17.jar!/org/apache/log4j/ConsoleAppender.class
[WARNING] org.apache.log4j.DailyRollingFileAppender scanned from multiple locations: jar:file:///home/ggfan/.m2/repository/log4j/apache-log4j-extras/1.2.17/apache-log4j-extras-1.2.17.jar!/org/apache/log4j/DailyRollingFileAppender.class, jar:file:///home/ggfan/.m2/repository/log4j/log4j/1.2.17/log4j-1.2.17.jar!/org/apache/log4j/DailyRollingFileAppender.class
[WARNING] org.apache.log4j.DefaultCategoryFactory scanned from multiple locations: jar:file:///home/ggfan/.m2/repository/log4j/apache-log4j-extras/1.2.17/apache-log4j-extras-1.2.17.jar!/org/apache/log4j/DefaultCategoryFactory.class, jar:file:///home/ggfan/.m2/repository/log4j/log4j/1.2.17/log4j-1.2.17.jar!/org/apache/log4j/DefaultCategoryFactory.class