hadoop初识--HelloHadoopV1
/*** HelloHadoop
* 此程序用来了解Hadoop的<key,value>,并且练习hadoop api 编程
*
* 测试方法：
* 1、将该程序打包在hadoop0.21.0平台上；打成jar包，并将jar包拷贝到usr/local/hadoop（hadoop的安装目录）下
* 2、格式化namenode：
* hadoop@wxy:/usr/local/hadoop$ ./bin/hadoop namenode -format
* 3、启动hadoop
* hadoop@wxy:/usr/local/hadoop$ ./bin/start-all.sh
* 4、查看hadoop运行情况 ￥jps
* 5、在hdfs上创建input文件夹，将文本文件READ.TXT拷贝到hdfs(/user/hadoop/input)上
http://dl.iteye.com/upload/attachment/503646/f49992ad-af59-334e-a3ee-59a3566c099f.png
http://dl.iteye.com/upload/attachment/503648/72a1d6dc-f08d-3a56-8594-12ac441b70eb.png
http://dl.iteye.com/upload/attachment/503650/7392ccc9-dcb4-3ec2-8b64-1d76c70b096c.png
* 6执行：
* hadoop@wxy:/usr/local/hadoop$ bin/hadoop jar HelloHadoop.jar
*7 查看运行结果
http://dl.iteye.com/upload/attachment/503665/1f6697bd-1400-347e-856f-2e41d7c47df8.png
如上图，产生/user/hadoop/output-hh1文件夹，文件夹中包含运行结果
http://dl.iteye.com/upload/attachment/503667/a5054e89-88a3-3d1d-8b44-d9c04135e0c2.png
*
*注意：
*1.在hdfs 上来源文档路径为 "/user/hadoop/input"
* 注意必须先放资料到此hdfs上的文件夹内，且文件夹内只能放文件，不能再放文件夹
*2. 运算完后，程序将执行结果放在hdfs 的输出路径为 "/user/$YOUR_NAME/output-hh1"
* 注意此文件夹为运算结束后才产生的，所以运算之前不会产生该文件夹
*
*浏览器中输入：http://localhost:50030/jobtracker.jsp查看运行状态
*/
package HelloHadoopV1;import java.io.IOException;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.fs.Path;import org.apache.hadoop.io.LongWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapreduce.Job;import org.apache.hadoop.mapreduce.Mapper;import org.apache.hadoop.mapreduce.Reducer;import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;/** * HelloHadoop * @author wxy * 此程序用来了解Hadoop的<key,value>,并且练习hadoop api 编程 **/public class HelloHadoop {static public class HelloMapper extends Mapper<LongWritable,Text,LongWritable,Text>{public void map(LongWritable key,Text value,Context context) throws IOException,InterruptedException {//将输入的资料，原封不动的写入输出context.write((LongWritable)key, (Text)value);}}static public class HelloReducer extends Reducer<LongWritable,Text,LongWritable,Text>{public void reduce(LongWritable key,Iterable<Text> values,Context context) throws IOException,InterruptedException {Text val = new Text();//取得values的值，放入val中for(Text str:values){val.set(str.toString());}//将获取的资料引入输出context.write(key, val);}}public static void main(String[] args)throws IOException,InterruptedException,ClassNotFoundException{//引入 ￥HADOOP_HOME/conf 启用默认配置Configuration conf = new Configuration();//定义一个job，宣告job取得conf并设定名称 Hadoop Hello WorldJob job = new Job(conf,"Hadoop Hello World");//设置运算主程序，即执行类job.setJarByClass(HelloHadoop.class);//设置输入路径FileInputFormat.setInputPaths(job,"input");//设置输出路径FileOutputFormat.setOutputPath(job,new Path("output-hh1"));//指定Map class，即设定Mapper的实现类job.setMapperClass(HelloMapper.class);//指定reduce class，即设定Reducer的实现类job.setReducerClass(HelloReducer.class);//开始运算job.waitForCompletion(true);}}
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