我NullPointerException在开始MapReduce工作时遇到了问题。它被SerializationFactory'sgetSerializer()方法抛出。我正在使用自定义InputSplit、、InputFormat和值类RecordReader。MapReduce
我知道在我的班级创建拆分后的某个时间InputFormat，但在创建RecordReader. 据我所知，它是在“清理暂存区”消息之后直接发生的。
getSerialization()通过在堆栈跟踪指示的位置检查 Hadoop 源，当接收到空Class<T>指针时，似乎正在发生错误。JobClientwriteNewSplits()像这样调用该方法：
Serializer<T> serializer = factory.getSerializer((Class<T>) split.getClass());
因此，我假设当getClass()在我的自定义对象上被调用时InputSplit，它会返回一个null指针，但这只是令人困惑。有任何想法吗？
错误的完整堆栈跟踪如下：
12/06/24 14:26:49 INFO mapred.JobClient: 清理暂存区 hdfs://localhost:54310/tmp/hadoop-s3cur3/mapred/staging/s3cur3/.staging/job_201206240915_0035
线程“主”java.lang.NullPointerException 中的异常
在 org.apache.hadoop.io.serializer.SerializationFactory.getSerializer(SerializationFactory.java:73)
在 org.apache.hadoop.mapreduce.split.JobSplitWriter.writeNewSplits(JobSplitWriter.java:123)
在 org.apache.hadoop.mapreduce.split.JobSplitWriter.createSplitFiles(JobSplitWriter.java:74)
在 org.apache.hadoop.mapred.JobClient.writeNewSplits(JobClient.java:968)
在 org.apache.hadoop.mapred.JobClient.writeSplits(JobClient.java:979)
在 org.apache.hadoop.mapred.JobClient.access$600(JobClient.java:174)
在 org.apache.hadoop.mapred.JobClient$2.run(JobClient.java:897)
在 org.apache.hadoop.mapred.JobClient$2.run(JobClient.java:850)
在 java.security.AccessController.doPrivileged（本机方法）
在 javax.security.auth.Subject.doAs(Subject.java:396)
在 org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1121)
在 org.apache.hadoop.mapred.JobClient.submitJobInternal(JobClient.java:850)
在 org.apache.hadoop.mapreduce.Job.submit(Job.java:500)
在 org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:530)
在 edu.cs.illinois.cogcomp.hadoopinterface.infrastructure.CuratorJob.start（CuratorJob.java:94）
在 edu.cs.illinois.cogcomp.hadoopinterface.HadoopInterface.main(HadoopInterface.java:58)
在 sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
在 sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
在 sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
在 java.lang.reflect.Method.invoke(Method.java:597)
在 org.apache.hadoop.util.RunJar.main(RunJar.java:156)
谢谢！
编辑：我的自定义 InputSplit 代码如下：
import . . .
/**
* A document directory within the input directory.
* Returned by DirectoryInputFormat.getSplits()
* and passed to DirectoryInputFormat.createRecordReader().
*
* Represents the data to be processed by an individual Map process.
*/
public class DirectorySplit extends InputSplit {
/**
* Constructs a DirectorySplit object
* @param docDirectoryInHDFS The location (in HDFS) of this
* document's directory, complete with all annotations.
* @param fs The filesystem associated with this job
*/
public DirectorySplit( Path docDirectoryInHDFS, FileSystem fs )
throws IOException {
this.inputPath = docDirectoryInHDFS;
hash = FileSystemHandler.getFileNameFromPath(inputPath);
this.fs = fs;
}
/**
* Get the size of the split so that the input splits can be sorted by size.
* Here, we calculate the size to be the number of bytes in the original
* document (i.e., ignoring all annotations).
*
* @return The number of characters in the original document
*/
@Override
public long getLength() throws IOException, InterruptedException {
Path origTxt = new Path( inputPath, "original.txt" );
HadoopInterface.logger.log( msg );
return FileSystemHandler.getFileSizeInBytes( origTxt, fs);
}
/**
* Get the list of nodes where the data for this split would be local.
* This list includes all nodes that contain any of the required data---it's
* up to Hadoop to decide which one to use.
*
* @return An array of the nodes for whom the split is local
* @throws IOException
* @throws InterruptedException
*/
@Override
public String[] getLocations() throws IOException, InterruptedException {
FileStatus status = fs.getFileStatus(inputPath);
BlockLocation[] blockLocs = fs.getFileBlockLocations( status, 0,
status.getLen() );
HashSet<String> allBlockHosts = new HashSet<String>();
for( BlockLocation blockLoc : blockLocs ) {
allBlockHosts.addAll( Arrays.asList( blockLoc.getHosts() ) );
}
return (String[])allBlockHosts.toArray();
}
/**
* @return The hash of the document that this split handles
*/
public String toString() {
return hash;
}
private Path inputPath;
private String hash;
private FileSystem fs;
}