我在尝试执行一个简单的MapReduce程序时得到NullPointerException。我无法理解问题出在哪里？
package MapReduce.HadMapReduce;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
public class RecCount extends Configured implements Tool {
public int run(String[] arg0) throws Exception {
Job job = Job.getInstance(getConf());
FileInputFormat.setInputPaths(job, new Path("C:\\singledeck.txt"));
FileOutputFormat.setOutputPath(job, new Path("C:\\temp123"));
return job.waitForCompletion(true) ? 0 : 1;
}
public static void main(String args[]) throws Exception {
System.exit(ToolRunner.run(new RecCount(), args));
}
}
错误是：
Exception in thread "main" java.lang.NullPointerException
at java.lang.ProcessBuilder.start(ProcessBuilder.java:1010)
at org.apache.hadoop.util.Shell.runCommand(Shell.java:483)
at org.apache.hadoop.util.Shell.run(Shell.java:456)
at org.apache.hadoop.util.Shell$ShellCommandExecutor.execute(Shell.java:722)
at org.apache.hadoop.util.Shell.execCommand(Shell.java:815)
at org.apache.hadoop.util.Shell.execCommand(Shell.java:798)
at org.apache.hadoop.fs.RawLocalFileSystem.setPermission(RawLocalFileSystem.java:731)
at org.apache.hadoop.fs.RawLocalFileSystem.mkOneDirWithMode(RawLocalFileSystem.java:489)
at org.apache.hadoop.fs.RawLocalFileSystem.mkdirsWithOptionalPermission(RawLocalFileSystem.java:530)
at org.apache.hadoop.fs.RawLocalFileSystem.mkdirs(RawLocalFileSystem.java:507)
at org.apache.hadoop.fs.FilterFileSystem.mkdirs(FilterFileSystem.java:305)
at org.apache.hadoop.mapreduce.JobSubmissionFiles.getStagingDir(JobSubmissionFiles.java:133)
at org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal(JobSubmitter.java:144)
at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1290)
at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1287)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1657)
at org.apache.hadoop.mapreduce.Job.submit(Job.java:1287)
at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:1308)
at MapReduce.HadMapReduce.RecCount.run(RecCount.java:22)
at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70)
at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:84)
at MapReduce.HadMapReduce.RecCount.main(RecCount.java:26)
这是幕后发生的逻辑：
ToolRunner正在调用以下run方法，此方法调用其他run方法（粘贴在此下方），如果是{{1}，则设置配置}。
null在上面的最后一个语句中，我调用了run方法，因为我实现了public static int run(Tool tool, String[] args) throws Exception {
return run(tool.getConf(), tool, args);
}
public static int run(Configuration conf, Tool tool, String[] args) throws Exception {
if (conf == null) {
conf = new Configuration();
}
GenericOptionsParser parser = new GenericOptionsParser(conf, args);
// set the configuration back, so that Tool can configure itself
tool.setConf(conf);
// get the args w/o generic hadoop args
String[] toolArgs = parser.getRemainingArgs();
return tool.run(toolArgs);
}
接口。我的代码中没有发现任何错误。如果你能找到，请告诉我。
有人可以解释我的代码有什么问题吗？