eclispe初次執行Hadoop時，我遇到的問題。
1、執行時，後臺顯示找不到在hdfs上的檔案，但是我在命令列執行時，可以查到檔案在hdfs上。
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" org.apache.hadoop.mapreduce.lib.input.InvalidInputException: Input path does not exist: file:/tiandongxue/word.txt
at org.apache.hadoop.mapreduce.lib.input.FileInputFormat.singleThreadedListStatus(FileInputFormat.java:321)
at org.apache.hadoop.mapreduce.lib.input.FileInputFormat.listStatus(FileInputFormat.java:264)
at org.apache.hadoop.mapreduce.lib.input.FileInputFormat.getSplits(FileInputFormat.java:385)
at org.apache.hadoop.mapreduce.JobSubmitter.writeNewSplits(JobSubmitter.java:493)
at org.apache.hadoop.mapreduce.JobSubmitter.writeSplits(JobSubmitter.java:510)
at org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal(JobSubmitter.java:394)
at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1285)
at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1282)
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:1614)
at org.apache.hadoop.mapreduce.Job.submit(Job.java:1282)
at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:1303)
at WordCount.main(WordCount.java:34)
我的檔案程式碼：
//設定Reduce相關屬性
job.setReducerClass(WCReducer.class);
job.setOutputKeyClass(Text.class);
job.setMapOutputValueClass(LongWritable.class);
FileOutputFormat.setOutputPath(job, new Path("/tiandongxue/result"));
解決方式：當我把檔案的路徑寫為絕對路徑 hdfs://master:9000/tiandongxue/word.txt 之後，就不報錯，但是出現另一個問題
程式執行到這裡時就不執行了，
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.
解決方式：通過百度檢視到需要新建一個 log4j.properties 檔案，他的作用就是日誌系統，控制輸出日誌的格式。內容為
# Configure logging for testing: optionally with log file
#log4j.rootLogger=debug,appender
log4j.rootLogger=info,appender
#log4j.rootLogger=error,appender
#\u8F93\u51FA\u5230\u63A7\u5236\u53F0
log4j.appender.appender=org.apache.log4j.ConsoleAppender
#\u6837\u5F0F\u4E3ATTCCLayout
log4j.appender.appender.layout=org.apache.log4j.TTCCLayout
這時在執行就可以成功執行了。