Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/log4j/Level

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/log4j/Level
    at org.apache.hadoop.mapred.JobConf.<clinit>(JobConf.java:357)
    at org.apache.hadoop.mapreduce.Job.getInstance(Job.java:186)
    at org.apache.hadoop.mapreduce.Job.getInstance(Job.java:206)
    at com.hadoop.hadoop_test.WordCount.main(WordCount.java:52)
Caused by: java.lang.ClassNotFoundException: org.apache.log4j.Level
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 4 more
在统计wordcount时，报一下错误，仔细分析了一下：

        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>

把log4j改1.2.14版本，错误消失。