apache/hadoop · error · IllegalArgumentException

Can not create a Path from an empty string

Error message

Can not create a Path from an empty string

What it means

org.apache.hadoop.fs.Path refuses construction from an empty string. checkPathArg() rejects zero-length input before any URI normalization, because an empty path has no meaningful filesystem location. It almost always indicates a truncated variable interpolation, an empty config value, or string manipulation that stripped all content.

Source

Thrown at hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/Path.java:173

        parentUri = new URI(parentUri.getScheme(), parentUri.getAuthority(),
                      parentUri.getPath()+"/", null, parentUri.getFragment());
      } catch (URISyntaxException e) {
        throw new IllegalArgumentException(e);
      }
    }
    URI resolved = parentUri.resolve(child.uri);
    initialize(resolved.getScheme(), resolved.getAuthority(),
               resolved.getPath(), resolved.getFragment());
  }

  private void checkPathArg( String path ) throws IllegalArgumentException {
    // disallow construction of a Path from an empty string
    if ( path == null ) {
      throw new IllegalArgumentException(
          "Can not create a Path from a null string");
    }
    if( path.length() == 0 ) {
       throw new IllegalArgumentException(
           "Can not create a Path from an empty string");
    }   
  }
  
  /**
   * Construct a path from a String.  Path strings are URIs, but with
   * unescaped elements and some additional normalization.
   *
   * @param pathString the path string
   */
  public Path(String pathString) throws IllegalArgumentException {
    checkPathArg( pathString );
    
    // We can't use 'new URI(String)' directly, since it assumes things are
    // escaped, which we don't require of Paths. 
    
    // add a slash in front of paths with Windows drive letters
    if (hasWindowsDrive(pathString) && pathString.charAt(0) != '/') {

View on GitHub (pinned to 2add963021)

Solutions

1. Print or log the raw string right before Path construction to confirm it is empty and identify the producer.
2. Fix the source of the value: give the config property real content, fix the shell variable/CLI argument, or fix the concatenation logic that yielded an empty result.
3. Add an early guard at input boundaries (CLI parser, config loader) that rejects empty strings with a descriptive message naming the parameter.
4. Treat empty as 'use default' only if your protocol explicitly defines that, e.g. path = (raw == null || raw.isEmpty()) ? "/user/me" : raw.

Example fix

// before
Path out = new Path(args[1]); // args[1] == "" from a mis-quoted shell call

// after
if (args.length < 2 || args[1].trim().isEmpty()) {
  throw new IllegalArgumentException("Output path argument is missing or empty");
}
Path out = new Path(args[1].trim());

public static Path safePath(String raw, String name) {
  if (raw == null || raw.trim().isEmpty()) {
    throw new IllegalArgumentException(name + " must be a non-empty path string");
  }
  return new Path(raw.trim());
}

try {
  return new Path(raw);
} catch (IllegalArgumentException e) {
  throw new IllegalArgumentException("Empty/invalid path for parameter 'output'", e);
}

When it happens

Trigger: Calling new Path("") directly, new Path(conf.get("key")) where the property exists but is empty (<value></value>), a concatenation like base + "/" + name where both parts are empty, or trimming user input that reduces to an empty string.

Common situations: core-site.xml with <property><name>fs.defaultFS</name><value></value></property>, a shell script exporting HDFS_PATH="" that the Java code reads, an empty CLI argument slot (app.sh "" /data), or template/placeholder substitution that produced nothing.

Related errors

• Can not create a Path from a null string
• Path part {s} from URI {p} is not a valid filename.
• mkdirs path arg is null
• Journal dir '{}' should be an absolute path
• Not a valid Boolean value for {property} in reconfSlowPeerPa

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/433cdbe4d403bd13. Report an issue: GitHub.