apache/hadoop · error · NullPointerException

Destination must not be null

Error message

Destination must not be null

What it means

Second guard clause of Storage.nativeCopyFileUnbuffered: NullPointerException when destFile is null while srcFile passed its check. Same contract as the source guard - both arguments must be non-null before the unbuffered copy starts.

Source

Thrown at hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/common/Storage.java:1330

   * not guaranteed that the operation will succeed.
   * If the modification operation fails, no indication is provided.
   *
   * @param srcFile  an existing file to copy, must not be {@code null}
   * @param destFile  the new file, must not be {@code null}
   * @param preserveFileDate  true if the file date of the copy
   *  should be the same as the original
   *
   * @throws NullPointerException if source or destination is {@code null}
   * @throws IOException if source or destination is invalid
   * @throws IOException if an IO error occurs during copying
   */
  public static void nativeCopyFileUnbuffered(File srcFile, File destFile,
      boolean preserveFileDate) throws IOException {
    if (srcFile == null) {
      throw new NullPointerException("Source must not be null");
    }
    if (destFile == null) {
      throw new NullPointerException("Destination must not be null");
    }
    if (srcFile.exists() == false) {
      throw new FileNotFoundException("Source '" + srcFile + "' does not exist");
    }
    if (srcFile.isDirectory()) {
      throw new IOException("Source '" + srcFile + "' exists but is a directory");
    }
    if (srcFile.getCanonicalPath().equals(destFile.getCanonicalPath())) {
      throw new IOException("Source '" + srcFile + "' and destination '" +
          destFile + "' are the same");
    }
    File parentFile = destFile.getParentFile();
    if (parentFile != null) {
      if (!parentFile.mkdirs() && !parentFile.isDirectory()) {
        throw new IOException("Destination '" + parentFile
            + "' directory cannot be created");
      }
    }

View on GitHub (pinned to 2add963021)

Solutions

1. Pass a non-null destFile
2. Fail fast at the call site: Objects.requireNonNull(destFile, "destFile")
3. Validate the output-directory configuration before constructing the destination path

Example fix

// before
Storage.nativeCopyFileUnbuffered(src, resolveDst(cfg), true); // resolveDst returns null
// after
File dst = Objects.requireNonNull(resolveDst(cfg), "output dir not configured");
Storage.nativeCopyFileUnbuffered(src, dst, true);

Objects.requireNonNull(destFile, "destFile must be resolved before copy");
File parent = destFile.getParentFile();
if (parent != null && !parent.isDirectory() && !parent.mkdirs()) {
  throw new IOException("cannot create " + parent);
}

static boolean isUsableDestination(File f) {
  return f != null && (f.getParentFile() == null || f.getParentFile().isDirectory());
}

When it happens

Trigger: Calling nativeCopyFileUnbuffered with a null destination File, typically from a caller that built the destination from a null-returning path lookup or an unset output directory setting.

Common situations: Destination directory config missing so the path builder returns null; tests passing null explicitly; partial refactors leaving the destination unresolved.

Related errors

• Source must not be null
• The filePath should not be null!
• Block cannot be null
• Provided block and location cannot be null
• Source '{srcFile}' does not exist

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/da39155fdd1057d2. Report an issue: GitHub.