java - hadoop - java.lang.RuntimeException : java. lang.InstantiationException 异常

Question

我正在尝试从客户端 (widows-7) 运行 map-reduce 程序，这是 map-reduce 类:

Configuration conf =  new Configuration();

    conf.addResource(new Path("C:\\app\\hadoop-2.0.0-cdh4.3.0\\etc\\hadoop\\core-site.xml"));
    conf.addResource(new Path("C:\\app\\hadoop-2.0.0-cdh4.3.0\\etc\\hadoop\\hdfs-site.xml"));

    conf.set("fs.defaultFS", "hdfs://host:8020");
    conf.set("mapred.job.tracker", "host:8021");

    Job job = new Job(conf, "mapRed");
    job.setMapperClass(MapClass.class);
    //job.setInputFormatClass(org.apache.hadoop.mapreduce.lib.input.TextInputFormat.class);
    int numreducers = 1;

    job.setNumReduceTasks(numreducers);
    job.setOutputKeyClass(Text.class);
    job.setOutputValueClass(Text.class);

    Path inp = new Path("/data/test");
    FileInputFormat.addInputPath(job, inp);
    FileOutputFormat.setOutputPath(job, new Path("/data"));
    System.exit(job.waitForCompletion(true) ? 0 : 1);

这个程序抛出异常:

    13/12/14 08:27:52 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Exception in thread "main" java.lang.RuntimeException: java.lang.InstantiationException
    at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:128)
    at org.apache.hadoop.fs.FileSystem.createFileSystem(FileSystem.java:2307)
    at org.apache.hadoop.fs.FileSystem.access$200(FileSystem.java:87)
    at org.apache.hadoop.fs.FileSystem$Cache.getInternal(FileSystem.java:2342)
    at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:2324)
    at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:351)
    at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:163)
    at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:335)
    at org.apache.hadoop.fs.Path.getFileSystem(Path.java:194)
    at org.apache.hadoop.mapreduce.lib.input.FileInputFormat.addInputPath(FileInputFormat.java:368)
    at org.gridedge.finalytics.MRTemplate.main(MRTemplate.java:55)
Caused by: java.lang.InstantiationException
    at sun.reflect.InstantiationExceptionConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:126)
    ... 10 more

我在这里发现了一个类似的问题 InstantiationException in hadoop map reduce program我将 FileInputFormat 更改为 TextInputFormat :

 TextInputFormat.addInputPath(job, inp);
 TextOutputFormat.setOutputPath(job, new Path("/data"));

错误保持不变，并在 FileInputFormat.addInputPath(job, inp); 行抛出

Answer 1

正确的配置是在 setInputFormat 方法中设置 TextInputFormat。该行似乎在您的代码中被注释了。请将其注释掉，然后尝试使用

FileInputFormat.addInputPaths。

要设置输入和输出格式，您可以看到以下行。

job.setInputFormatClass(TextInputFormat.class);job.setOutputFormatClass(TextOutputFormat.class);

如果您仍然遇到任何错误，请告诉我。