自定义MapReduce输入格式 - 找不到构造函数

Question

我正在为Hadoop 0.20.2编写一个自定义的InputFormat,并且遇到NoSuchMethodException我无法摆脱.我开始时:

public class ConnectionInputFormat extends FileInputFormat<Text, Connection> {

    @Override
    public RecordReader<Text, Connection> createRecordReader(InputSplit split, TaskAttemptContext context) throws IOException, InterruptedException {
        return new ConnectionRecordReader();
    }
}

运行时出现此错误:

Exception in thread "main" java.lang.RuntimeException: java.lang.NoSuchMethodException: testingground.TestInputJob$ConnectionInputFormat.<init>()
at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:115)
at org.apache.hadoop.mapred.JobClient.writeNewSplits(JobClient.java:882)
at org.apache.hadoop.mapred.JobClient.submitJobInternal(JobClient.java:779)
at org.apache.hadoop.mapreduce.Job.submit(Job.java:432)
at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:447)
at testingground.TestInputJob.run(TestInputJob.java:141)
at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:65)
at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:79)
at testingground.TestInputJob.main(TestInputJob.java:156)
Caused by: java.lang.NoSuchMethodException: testingground.TestInputJob$ConnectionInputFormat.<init>()
at java.lang.Class.getConstructor0(Class.java:2706)
at java.lang.Class.getDeclaredConstructor(Class.java:1985)
at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:109)
... 8 more
Java Result: 1

在初始化错误并在线研究之后,我认为可能是因为我没有零参数构造函数,所以我添加了一个:

public class ConnectionInputFormat extends FileInputFormat<Text, Connection> {

    public ConnectionInputFormat() {
        System.out.println("NetflowInputFormat Constructor");
    }

    @Override
    public RecordReader<Text, Connection> createRecordReader(InputSplit split, TaskAttemptContext context) throws IOException, InterruptedException {
        return new ConnectionRecordReader();
    }
}

这也没用,所以我添加了第二个构造函数,它接受了任意数量的对象:

public class ConnectionInputFormat extends FileInputFormat<Text, Connection> {

    public ConnectionInputFormat() {
        System.out.println("NetflowInputFormat Constructor");
    }

    public ConnectionInputFormat(Object... o) {
        System.out.println("NetflowInputFormat Constructor");
    }

    @Override
    public RecordReader<Text, Connection> createRecordReader(InputSplit split, TaskAttemptContext context) throws IOException, InterruptedException {
        return new ConnectionRecordReader();
    }
}

仍然得到相同的错误,并且到目前为止找不到解决方案是不成功的.

全电流源:http://pastebin.com/2XyW5ZSS

Answer 1

您的ConnectionInputFormat类应该是静态的.非静态嵌套类在每个构造函数中都添加了隐含的"this".因此,除非将类声明为static,否则no-arg构造函数实际上具有不可见的参数.