www.aboutyun.com教你如何查看API及使用hadoop新api编程：hadoop2.4新api与旧api调用例子对比说明问题导读：一直想写hadoop新旧api之间的关系，这对于爱好编程的程序猿来讲，是必备的。1.hadoop中mapred与mapreduce包，那个是被弃用的？2.hadoop旧api如何初始化job？3.hadoop新api使用那个函数来初始化job对象？程序说明：下面的mapreduce程序的功能只是计算文件booklist.log的行数，最后输出结果。分别调用旧包和新包的方法编写了两分带有main函数的java代码。a,新建了mapreduce工程后，先把hadoop的配置目录下的xml都拷贝到src目录下。b,在工程src同级目录旁建立conf目录，并放一个log4j.properties文件。c,src目录下建立bookCount目录，然后再添加后面的子java文件。d,右击"runasapplication"或选择hadoop插件菜单"runonhadoop"来触发执行MapReduce程序即可运行。www.aboutyun.com生成要分析的输入文件vinamelist.log添加以下内容即可：namenamenamenamenamenamenamenamenamenamenamename保存退出。执行的前请通过hdfs的copyFromLocal命令拷贝到hdfs的/user/hduser用户目录下。老API使用mapred包的代码www.aboutyun.com文件BookCount.java：packagebookCount;importjava.io.IOException;importjava.util.Iterator;importorg.apache.hadoop.fs.Path;importorg.apache.hadoop.io.IntWritable;importorg.apache.hadoop.io.LongWritable;importorg.apache.hadoop.io.Text;importorg.apache.hadoop.mapred.FileInputFormat;importorg.apache.hadoop.mapred.FileOutputFormat;importorg.apache.hadoop.mapred.JobClient;importorg.apache.hadoop.mapred.JobConf;importorg.apache.hadoop.mapred.MapReduceBase;importorg.apache.hadoop.mapred.Mapper;importorg.apache.hadoop.mapred.OutputCollector;importorg.apache.hadoop.mapred.Reducer;importorg.apache.hadoop.mapred.Reporter;importorg.apache.log4j.Logger;www.aboutyun.comimportorg.apache.log4j.PropertyConfigurator;publicclassBookCount{publicstaticLoggerlogger=Logger.getLogger(BookCount.class);publicstaticvoidmain(String[]args)throwsIOException{PropertyConfigurator.configure("conf/log4j.properties");logger=Logger.getLogger(BookCount.class);logger.info("AnaSpeedMrstarting");System.setProperty("HADOOP_USER_NAME","hduser");JobConfconf=newJobConf(BookCount.class);conf.setJobName("bookCount_sample_job");FileInputFormat.setInputPaths(conf,newPath("booklist.log"));FileOutputFor