用java下载hdfs文件报NullPointerException

最新推荐文章于 2023-09-26 16:36:03 发布

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最新推荐文章于 2023-09-26 16:36:03 发布

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文章标签： java 大数据 shell

原文链接：http://www.cnblogs.com/zhuzhixijiang/p/5141454.html

本文介绍了一个关于使用HDFS API下载文件时遇到NullPointerException的问题及其解决方案。错误发生在尝试使用fs.copyToLocalFile方法时，通过调整参数设置为fs.copyToLocalFile(false, hdfsPath, localPath, true)，成功解决了该问题。

用fs.copyToLocalFile( hdfsPath,localPath);下载hdfs的文件会报NullPointerException,具体报错为:

java.lang.NullPointerException
    at java.lang.ProcessBuilder.start(ProcessBuilder.java:1012)
    at org.apache.hadoop.util.Shell.runCommand(Shell.java:487)
    at org.apache.hadoop.util.Shell.run(Shell.java:460)
    at org.apache.hadoop.util.Shell$ShellCommandExecutor.execute(Shell.java:720)
    at org.apache.hadoop.util.Shell.execCommand(Shell.java:813)
    at org.apache.hadoop.util.Shell.execCommand(Shell.java:796)
    at org.apache.hadoop.fs.RawLocalFileSystem.setPermission(RawLocalFileSystem.java:656)
    at org.apache.hadoop.fs.FilterFileSystem.setPermission(FilterFileSystem.java:490)
    at org.apache.hadoop.fs.ChecksumFileSystem.create(ChecksumFileSystem.java:462)
    at org.apache.hadoop.fs.ChecksumFileSystem.create(ChecksumFileSystem.java:428)
    at org.apache.hadoop.fs.FileSystem.create(FileSystem.java:908)
    at org.apache.hadoop.fs.FileSystem.create(FileSystem.java:889)
    at org.apache.hadoop.fs.FileSystem.create(FileSystem.java:786)
    at org.apache.hadoop.fs.FileUtil.copy(FileUtil.java:365)
    at org.apache.hadoop.fs.FileUtil.copy(FileUtil.java:338)
    at org.apache.hadoop.fs.FileUtil.copy(FileUtil.java:289)
    at org.apache.hadoop.fs.FileSystem.copyToLocalFile(FileSystem.java:1970)
    at org.apache.hadoop.fs.FileSystem.copyToLocalFile(FileSystem.java:1939)
    at org.apache.hadoop.fs.FileSystem.copyToLocalFile(FileSystem.java:1915)
    at hadoop.downFile.downloadFileorDirectoryOnHDFS(downFile.java:29)
    at hadoop.downFile.main(downFile.java:12)