项目工程见：
1.mapper代码: WcMapper
2.reducer代码：WcReducer
3.job调用：
4.使用pom文件配置打包方式：
5.会在工程下生成一个jar：且修改jar包为hadoop-demo.jar
6.jar包上传到linux系统上
7.将待统计文件words.txt上传到hdfs上
Hadoop fs –put /jurf_temp_data/words.txt /words
8．执行jar：
[root@naidong jurf_temp_data]# hadoop jar hadoop-demo.jar
2019-01-04 11:59:50,916 INFO client.RMProxy: Connecting to ResourceManager at /0.0.0.0:8032
2019-01-04 11:59:57,490 WARN mapreduce.JobResourceUploader: Hadoop command-line option parsing not performed. Implement the Tool interface and execute your application with ToolRunner to remedy this.
2019-01-04 11:59:57,578 INFO mapreduce.JobResourceUploader: Disabling Erasure Coding for path: /tmp/hadoop-yarn/staging/root/.staging/job_1546572216242_0003
2019-01-04 12:00:00,103 INFO input.FileInputFormat: Total input files to process : 1
2019-01-04 12:00:01,179 INFO mapreduce.JobSubmitter: number of splits:1
2019-01-04 12:00:01,692 INFO Configuration.deprecation: yarn.resourcemanager.system-metrics-publisher.enabled is deprecated. Instead, use yarn.system-metrics-publisher.enabled
2019-01-04 12:00:03,131 INFO mapreduce.JobSubmitter: Submitting tokens for job: job_1546572216242_0003
2019-01-04 12:00:03,135 INFO mapreduce.JobSubmitter: Executing with tokens: []
2019-01-04 12:00:04,502 INFO conf.Configuration: resource-types.xml not found
2019-01-04 12:00:04,503 INFO resource.ResourceUtils: Unable to find 'resource-types.xml'.
2019-01-04 12:00:05,256 INFO impl.YarnClientImpl: Submitted application application_1546572216242_0003
2019-01-04 12:00:05,504 INFO mapreduce.Job: The url to track the job: http://naidong:8088/proxy/application_1546572216242_0003/
2019-01-04 12:00:05,544 INFO mapreduce.Job: Running job: job_1546572216242_0003
2019-01-04 12:00:33,928 INFO mapreduce.Job: Job job_1546572216242_0003 running in uber mode : false
2019-01-04 12:00:33,952 INFO mapreduce.Job: map 0% reduce 0%
2019-01-04 12:00:58,116 INFO mapreduce.Job: map 100% reduce 0%
2019-01-04 12:01:30,074 INFO mapreduce.Job: map 100% reduce 100%
2019-01-04 12:01:32,169 INFO mapreduce.Job: Job job_1546572216242_0003 completed successfully
2019-01-04 12:01:32,782 INFO mapreduce.Job: Counters: 53
File System Counters
FILE: Number of bytes read=195
FILE: Number of bytes written=426255
FILE: Number of read operations=0
FILE: Number of large read operations=0
FILE: Number of write operations=0
HDFS: Number of bytes read=170
HDFS: Number of bytes written=76
HDFS: Number of read operations=8
HDFS: Number of large read operations=0
HDFS: Number of write operations=2
Job Counters
Launched map tasks=1
Launched reduce tasks=1
Data-local map tasks=1
Total time spent by all maps in occupied slots (ms)=41852
Total time spent by all reduces in occupied slots (ms)=87912
Total time spent by all map tasks (ms)=20926
Total time spent by all reduce tasks (ms)=29304
Total vcore-milliseconds taken by all map tasks=20926
Total vcore-milliseconds taken by all reduce tasks=29304
Total megabyte-milliseconds taken by all map tasks=42856448
Total megabyte-milliseconds taken by all reduce tasks=90021888
Map-Reduce Framework
Map input records=6
Map output records=12
Map output bytes=165
Map output materialized bytes=195
Input split bytes=97
Combine input records=0
Combine output records=0
Reduce input groups=10
Reduce shuffle bytes=195
Reduce input records=12
Reduce output records=10
Spilled Records=24
Shuffled Maps =1
Failed Shuffles=0
Merged Map outputs=1
GC time elapsed (ms)=461
CPU time spent (ms)=5640
Physical memory (bytes) snapshot=371195904
Virtual memory (bytes) snapshot=7103193088
Total committed heap usage (bytes)=165810176
Peak Map Physical memory (bytes)=229015552
Peak Map Virtual memory (bytes)=2739154944
Peak Reduce Physical memory (bytes)=142180352
Peak Reduce Virtual memory (bytes)=4364038144
Shuffle Errors
BAD_ID=0
CONNECTION=0
IO_ERROR=0
WRONG_LENGTH=0
WRONG_MAP=0
WRONG_REDUCE=0
File Input Format Counters
Bytes Read=73
File Output Format Counters
Bytes Written=76
2019-01-04 12:01:42,813 WARN util.ShutdownHookManager: ShutdownHook '' timeout, java.util.concurrent.TimeoutException
java.util.concurrent.TimeoutException
at java.util.concurrent.FutureTask.get(FutureTask.java:205)
at org.apache.hadoop.util.ShutdownHookManager$1.run(ShutdownHookManager.java:68)
[root@naidong jurf_temp_data]#h
7.查看统计结果：
结果文件一般由三部分组成：
1) _SUCCESS文件：表示MapReduce运行成功。
2) Part-r-00000文件：存放结果，也是默认生成的结果文件。