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我正在按照mahout 站点上的说明将现有文件转换为序列文件：

VectorWriter vectorWriter = SequenceFile.createWriter(filesystem,
                                                  configuration,
                                                  outfile,
                                                  LongWritable.class,
                                                  SparseVector.class);

long numDocs = vectorWriter.write(new VectorIterable(), Long.MAX_VALUE);

我已将 mahout jar 包含在我的 maven 项目中：

    <dependency>
        <groupId>org.apache.mahout</groupId>
        <artifactId>mahout-core</artifactId>
        <version>0.9</version>
    </dependency>

但它不会写入文件。

我收到此错误：

Caused by: java.lang.NullPointerException
at org.apache.hadoop.io.serializer.SerializationFactory.getSerializer(SerializationFactory.java:73)
at org.apache.hadoop.io.SequenceFile$Writer.init(SequenceFile.java:963)
at org.apache.hadoop.io.SequenceFile$RecordCompressWriter.<init>(SequenceFile.java:1136)
at org.apache.hadoop.io.SequenceFile.createWriter(SequenceFile.java:397)
at org.apache.hadoop.io.SequenceFile.createWriter(SequenceFile.java:284)
at org.apache.hadoop.io.SequenceFile.createWriter(SequenceFile.java:265)

经进一步调查，原因如下：

Serilization class not found: java.lang.ClassNotFoundException: org.apache.hadoop.io.serializer.WritableSerialization

这表明我缺少一个罐子——有人知道是哪一个吗？

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1 回答 1

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问题是我在 Lenskit 中使用它，并且Configuration该类尝试使用Thread.currentThread().getContextClassLoader()哪个（无论出于何种原因）没有 mahout 或 hadoop 包。完整的代码是：

final Configuration configuration = new Configuration();
configuration.setClassLoader(Configuration.class.getClassLoader());

final Path path = new Path(POINTS_PATH + "/pointsFile");

LocalFileSystem fs = new LocalFileSystem();
fs.initialize(URI.create(POINTS_PATH + "/pointsFile"), configuration);

final SequenceFile.Writer writer =
        SequenceFile.createWriter(
                fs,
                configuration,
                path,
                Text.class,
                VectorWritable.class);
于 2015-03-11T14:33:44.527 回答