hadoop 版本兼容有关问题

hadoop 版本兼容问题

? 目前学习hadoop的书籍资料还不算多，在学习hadoop权威指南时，编写代码示例出现错误，代码为查找最好气温：

?public class MaxTemperature {

  public static void main(String[] args) throws IOException {    if (args.length != 2) {      System.err.println("Usage: MaxTemperature <input path> <output path>");      System.exit(-1);    }        JobConf conf = new JobConf(MaxTemperature.class);    conf.setJobName("Max temperature");    FileInputFormat.addInputPath(conf, new Path(args[0]));    FileOutputFormat.setOutputPath(conf, new Path(args[1]));        conf.setMapperClass(MaxTemperatureMapper.class);    conf.setReducerClass(MaxTemperatureReducer.class);    conf.setOutputKeyClass(Text.class);    conf.setOutputValueClass(IntWritable.class);    JobClient.runJob(conf);  }}

?public class MaxTemperatureMapper extends MapReduceBase

  implements Mapper<LongWritable, Text, Text, IntWritable> {  private static final int MISSING = 9999;    public void map(LongWritable key, Text value,      OutputCollector<Text, IntWritable> output, Reporter reporter)      throws IOException {        String line = value.toString();    String year = line.substring(15, 19);    int airTemperature;    if (line.charAt(87) == '+') { // parseInt doesn't like leading plus signs      airTemperature = Integer.parseInt(line.substring(88, 92));    } else {      airTemperature = Integer.parseInt(line.substring(87, 92));    }    String quality = line.substring(92, 93);    if (airTemperature != MISSING && quality.matches("[01459]")) {      output.collect(new Text(year), new IntWritable(airTemperature));    }  }}

?public class MaxTemperatureReducer extends MapReduceBase

  implements Reducer<Text, IntWritable, Text, IntWritable> {  public void reduce(Text key, Iterator<IntWritable> values,      OutputCollector<Text, IntWritable> output, Reporter reporter)      throws IOException {        int maxValue = Integer.MIN_VALUE;    while (values.hasNext()) {      maxValue = Math.max(maxValue, values.next().get());    }    output.collect(key, new IntWritable(maxValue));  }}

?

我安装的hadoop为0.20.2版本的，在执行该代码是显示"Usage: MaxTemperature <input path> <output path>",说明是一开始就报错了。看来是版本不一致，代码没有兼容造成，按照新的方式编写相应代码：

public class NewMaxTemperature {    static class NewMaxTemperatureMapper    /*[*/extends Mapper<LongWritable, Text, Text, IntWritable>/*]*/ {    private static final int MISSING = 9999;        public void map(LongWritable key, Text value, /*[*/Context context/*]*/)        throws IOException, /*[*/InterruptedException/*]*/ {            String line = value.toString();      String year = line.substring(15, 19);      int airTemperature;      if (line.charAt(87) == '+') { // parseInt doesn't like leading plus signs        airTemperature = Integer.parseInt(line.substring(88, 92));      } else {        airTemperature = Integer.parseInt(line.substring(87, 92));      }      String quality = line.substring(92, 93);      if (airTemperature != MISSING && quality.matches("[01459]")) {        /*[*/context.write/*]*/(new Text(year), new IntWritable(airTemperature));      }    }  }    static class NewMaxTemperatureReducer    /*[*/extends Reducer<Text, IntWritable, Text, IntWritable>/*]*/ {      public void reduce(Text key, /*[*/Iterable/*]*/<IntWritable> values,        /*[*/Context context/*]*/)        throws IOException, /*[*/InterruptedException/*]*/ {            int maxValue = Integer.MIN_VALUE;      for (IntWritable value : values) {        maxValue = Math.max(maxValue, value.get());      }      /*[*/context.write/*]*/(key, new IntWritable(maxValue));    }  }  public static void main(String[] args) throws Exception {    if (args.length != 2) {      System.err.println("Usage: NewMaxTemperature <input path> <output path>");      System.exit(-1);    }        /*[*/Job job = new Job();    job.setJarByClass(NewMaxTemperature.class);/*]*/    FileInputFormat.addInputPath(job, new Path(args[0]));    FileOutputFormat.setOutputPath(job, new Path(args[1]));        job.setMapperClass(NewMaxTemperatureMapper.class);    job.setReducerClass(NewMaxTemperatureReducer.class);    job.setOutputKeyClass(Text.class);    job.setOutputValueClass(IntWritable.class);        /*[*/System.exit(job.waitForCompletion(true) ? 0 : 1);/*]*/  }}