log4j-over-slf4j.jar AND slf4j-log4j12.jar 依赖冲突解决方案

使用maven构建项目时，若是项目中有log4j的依赖，在运行程序时可能会出如今同一个类中log4j-over-slf4j.jar和 slf4j-log4j12.jar冲突的问题：

项目报错内容为：

Exception in thread "main" java.lang.ExceptionInInitializerError
    at org.apache.log4j.LogManager.getLogger(LogManager.java:44)
    at org.slf4j.impl.Log4jLoggerFactory.getLogger(Log4jLoggerFactory.java:66)
    at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:270)
    at org.apache.commons.logging.impl.SLF4JLogFactory.getInstance(SLF4JLogFactory.java:155)
    at org.apache.commons.logging.impl.SLF4JLogFactory.getInstance(SLF4JLogFactory.java:132)
    at org.apache.commons.logging.LogFactory.getLog(LogFactory.java:657)
    at org.apache.hadoop.conf.Configuration.<clinit>(Configuration.java:173)

Caused by: java.lang.IllegalStateException: Detected both log4j-over-slf4j.jar AND slf4j-log4j12.jar on the class path, preempting StackOverflowError. See also http://www.slf4j.org/codes.html#log4jDelegationLoop for more details.
    at org.apache.log4j.Log4jLoggerFactory.<clinit>(Log4jLoggerFactory.java:49)
    ... 8 more

 

缘由是：log4j-over-slf4j和slf4j-log4j12是跟Java日志系统相关的两个jar包，当它们同时出如今classpath下时，就可能会引发堆栈溢出异常。

解决办法：pom.xml文件中，在使用到的依赖包中添加<exclusion>标签将slf4j-log4j12.jar排除便可：

例如：红色字体是排除的内容

       <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-client</artifactId>
            <version>2.6.0</version>
                <exclusions>
                <exclusion>
                    <groupId>org.slf4j</groupId>
                    <artifactId>slf4j-log4j12</artifactId>
                </exclusion>
            </exclusions>
        </dependency>