windows上eclipse運行hadoop程序報NullPointerException錯 log4j:WARN No appenders could be found for logger (org.apache.hadoop.metrics2.lib.MutableMetricsFactory). log4j:WARN Please initialize the log4j system properly. log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info. Exception in thread "main" java.lang.NullPointerException ?? ?at java.lang.ProcessBuilder.start(ProcessBuilder.java:1010) ?? ?at org.apache.hadoop.util.Shell.runCommand(Shell.java:482) ?? ?at org.apache.hadoop.util.Shell.run(Shell.java:455) ?? ?at org.apache.hadoop.util.Shell$ShellCommandExecutor.execute(Shell.java:715) ?? ?at org.apache.hadoop.util.Shell.execCommand(Shell.java:808) ?? ?at org.apache.hadoop.util.Shell.execCommand(Shell.java:791) ?? ?at org.apache.hadoop.fs.RawLocalFileSystem.setPermission(RawLocalFileSystem.java:656) ?? ?at org.apache.hadoop.fs.RawLocalFileSystem.mkdirs(RawLocalFileSystem.java:444) ?? ?at org.apache.hadoop.fs.FilterFileSystem.mkdirs(FilterFileSystem.java:293) ?? ?at org.apache.hadoop.mapreduce.JobSubmissionFiles.getStagingDir(JobSubmissionFiles.java:133) ?? ?at org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal(JobSubmitter.java:437) ?? ?at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1296) ?? ?at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1293) ?? ?at java.security.AccessController.doPrivileged(Native Method) ?? ?at javax.security.auth.Subject.doAs(Subject.java:415) ?? ?at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1628) ?? ?at org.apache.hadoop.mapreduce.Job.submit(Job.java:1293) ?? ?at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:1314) ?? ?at com.lxz.mr.WCApp.main(WCApp.java:27) 原因是hadoop.dll文件和winutils.exe文件缺失了。解決步驟為： 1，下載這兩個文件，下載地址：https://download.csdn.net/download/luxiangzhou/10635946 2，解壓之后，把hadoop.dll拷貝到C:\Windows\System32下面 3，創建環境變量HADOOP_HOME，然后把winutils.exe文件拷貝到${HADOOP_HOME}/bin目錄下