Hadoop客户端Java代码.zip

package cn.itcast.hadoop; import java.io.IOException; import java.util.StringTokenizer; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.Mapper; import org.apache.hadoop.mapreduce.Mapper.Context; import org.apache.hadoop.mapreduce.Reducer; import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; public class MyWordCount { public static class MyMapper extends Mapper<Object, Text, Text, IntWritable> { private final static IntWritable one = new IntWritable(1);// 类似于int类型 private Text word = new Text(); // 可以理解成String类型 public void map(Object key, Text value, Context context) throws IOException, InterruptedException { System.err.println(key + "," + value); // 默认情况下即根据空格分隔字符串 StringTokenizer itr = new StringTokenizer(value.toString()); while (itr.hasMoreTokens()) { word.set(itr.nextToken()); context.write(word, one); } }; } // Reducer<KEYIN, VALUEIN, KEYOUT, VALUEOUT> public static class MyReducer extends Reducer<Text, IntWritable, Text, IntWritable> { private IntWritable result = new IntWritable(); protected void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException { System.err.println(key + "," + values); int sum = 0; for (IntWritable val : values) { sum += val.get(); } result.set(sum); ; context.write(key, result);// 这是最后结果 }; } public static void main(String[] args) throws Exception { // 声明配置信息 Configuration conf = new Configuration(); // 声明Job Job job = new Job(conf, "Word Count"); // 设置工作类 job.setJarByClass(MyWordCount.class); // 设置mapper类 job.setMapperClass(MyMapper.class); // 可选 job.setCombinerClass(MyReducer.class); // 设置合并计算类 job.setReducerClass(MyReducer.class); // 设置key为String类型 job.setOutputKeyClass(Text.class); // 设置value为int类型 job.setOutputValueClass(IntWritable.class); // 设置或是接收输入输出 FileInputFormat.setInputPaths(job, new Path("/test/wordcount.txt")); FileOutputFormat.setOutputPath(job, new Path("/test/count")); // 执行 System.exit(job.waitForCompletion(true) ? 0 : 1); } }