[Nutch]編譯hadoop出現object[]無法轉換爲K[]問題解決

1. 問題描述

在使用JDK8編譯hadoop 1.2.1的時候會出現object[]無法轉換爲K[]的問題，如下：

2. 問題解決

（1）打開hadoop目錄下的InputSampler.java文件，路徑如下：
hadoop-1.2.1\src\mapred\org\apache\hadoop\mapreduce\lib\partition\InputSampler.java

（2）大概319行找到如下內容：

    final InputFormat inf = 
        ReflectionUtils.newInstance(job.getInputFormatClass(), conf);
    int numPartitions = job.getNumReduceTasks();
    K[] samples = sampler.getSample(inf, job);
    LOG.info("Using " + samples.length + " samples");
    RawComparator<K> comparator =
      (RawComparator<K>) job.getSortComparator();

將其修改爲：

    final InputFormat inf = 
        ReflectionUtils.newInstance(job.getInputFormatClass(), conf);
    int numPartitions = job.getNumReduceTasks();
    K[] samples = (K[])sampler.getSample(inf, job);
    LOG.info("Using " + samples.length + " samples");
    RawComparator<K> comparator =
      (RawComparator<K>) job.getSortComparator();

如下圖：

3. 重新編譯