在 windows 上運行 MapReduce 時報如下異常

Exception in thread "main" java.lang.UnsatisfiedLinkError: org.apache.hadoop.io.nativeio.NativeIO$Windows.access0(Ljava/lang/String;I)Z
	at org.apache.hadoop.io.nativeio.NativeIO$Windows.access0(Native Method)
	at org.apache.hadoop.io.nativeio.NativeIO$Windows.access(NativeIO.java:606)
	at org.apache.hadoop.fs.FileUtil.canRead(FileUtil.java:998)
	at org.apache.hadoop.util.DiskChecker.checkAccessByFileMethods(DiskChecker.java:160)
	at org.apache.hadoop.util.DiskChecker.checkDirInternal(DiskChecker.java:100)
	at org.apache.hadoop.util.DiskChecker.checkDir(DiskChecker.java:77)
	at org.apache.hadoop.fs.LocalDirAllocator$AllocatorPerContext.confChanged(LocalDirAllocator.java:315)
	at org.apache.hadoop.fs.LocalDirAllocator$AllocatorPerContext.getLocalPathForWrite(LocalDirAllocator.java:378)
	at org.apache.hadoop.fs.LocalDirAllocator.getLocalPathForWrite(LocalDirAllocator.java:152)
	at org.apache.hadoop.fs.LocalDirAllocator.getLocalPathForWrite(LocalDirAllocator.java:133)
	at org.apache.hadoop.fs.LocalDirAllocator.getLocalPathForWrite(LocalDirAllocator.java:117)
	at org.apache.hadoop.mapred.LocalDistributedCacheManager.setup(LocalDistributedCacheManager.java:124)
	at org.apache.hadoop.mapred.LocalJobRunner$Job.<init>(LocalJobRunner.java:171)
	at org.apache.hadoop.mapred.LocalJobRunner.submitJob(LocalJobRunner.java:760)
	at org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal(JobSubmitter.java:253)
	at org.apache.hadoop.mapreduce.Job$11.run(Job.java:1570)
	at org.apache.hadoop.mapreduce.Job$11.run(Job.java:1567)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAs(Subject.java:422)
	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1893)
	at org.apache.hadoop.mapreduce.Job.submit(Job.java:1567)
	at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:1588)
	at test.mapreduce.wordcount.WordcountDriver.main(WordcountDriver.java:56)

搜索相關問題后，已解決

前提：

確保 hadoop/bin 目錄下的文件是完整的，直接從 apache 下載的會缺少文件，可以自己編譯或從 GitHub 上下載其他人編譯好的文件

確保軟件 32 位或 64 位，保持一致

解決方法有如下兩種

1.手動加載 hadoop.dll，指定 hadoop 目錄

static {
    try {
        // 設置 HADOOP_HOME 目錄
        System.setProperty("hadoop.home.dir", "D:/DevelopTools/hadoop-2.9.2/");
        // 加載庫文件
        System.load("D:/DevelopTools/hadoop-2.9.2/bin/hadoop.dll");
    } catch (UnsatisfiedLinkError e) {
        System.err.println("Native code library failed to load.\n" + e);
        System.exit(1);
    }
}

2.覆蓋修改源碼中的代碼

復制 org.apache.hadoop.io.nativeio.NativeIO 到自己的項目，保持和源碼包路徑一致

修改 access() 方法返回值，原代碼如下

修改成如下，直接返回

private static native boolean access0(String var0, int var1);

public static boolean access(String path, NativeIO.Windows.AccessRight desiredAccess) throws IOException {
    return true;
}

https://blog.csdn.net/cor_twi/article/details/40891393

https://blog.csdn.net/congcong68/article/details/42043093

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