apache/hadoop · error · IllegalArgumentException

{name} cannot be null

Error message

{name} cannot be null

What it means

Check.notNull(obj, name) is the httpfs library's argument guard: it throws IllegalArgumentException('<name> cannot be null') when a caller passes null to any API parameter guarded by it (for example the 'user'/'conf' arguments of FileSystemAccess.execute and createFileSystemInternal). This is a programmer/argument error, not an environment problem.

Source

Thrown at hadoop-hdfs-project/hadoop-hdfs-httpfs/src/main/java/org/apache/hadoop/lib/util/Check.java:47

 * <p>
 * Commonly used for method arguments preconditions.
 */
@InterfaceAudience.Private
public class Check {

  /**
   * Verifies a variable is not NULL.
   *
   * @param obj the variable to check.
   * @param name the name to use in the exception message.
   *
   * @return the variable.
   *
   * @throws IllegalArgumentException if the variable is NULL.
   */
  public static <T> T notNull(T obj, String name) {
    if (obj == null) {
      throw new IllegalArgumentException(name + " cannot be null");
    }
    return obj;
  }

  /**
   * Verifies a list does not have any NULL elements.
   *
   * @param list the list to check.
   * @param name the name to use in the exception message.
   *
   * @return the list.
   *
   * @throws IllegalArgumentException if the list has NULL elements.
   */
  public static <T> List<T> notNullElements(List<T> list, String name) {
    notNull(list, name);
    for (int i = 0; i < list.size(); i++) {
      notNull(list.get(i), MessageFormat.format("list [{0}] element [{1}]", name, i));

View on GitHub (pinned to 2add963021)

Solutions

1. Look at the exception message - it names the exact argument that was null
2. Fix the caller to pass a non-null value (e.g. reject requests without a user parameter with a 4xx before reaching the service)
3. For 'user', validate the incoming proxy/doAs parameter at the HTTP boundary
4. Add unit tests covering the missing-argument path

Example fix

// before
String user = request.getParameter("user.name");
fsAccess.execute(user, conf, executor); // null user -> IllegalArgumentException

// after
String user = request.getParameter("user.name");
if (user == null || user.isEmpty()) { throw new IllegalArgumentException("user.name required"); }
fsAccess.execute(user, conf, executor);

import java.util.Objects;

String user = Objects.requireNonNullElse(requestedUser, "");
if (user.isEmpty()) { throw new IllegalArgumentException("user required"); }
// only reach guarded APIs with non-null arguments
fsAccess.execute(user, Objects.requireNonNull(conf, "conf"), executor);

static boolean isUsableUser(String s) {
  return s != null && !s.isEmpty();
}

try {
  fsAccess.execute(user, conf, executor);
} catch (IllegalArgumentException ex) {
  // message names the null argument, e.g. 'user cannot be null' - caller bug, do not retry
  throw new BadRequestException(ex.getMessage(), ex);
}

When it happens

Trigger: Calling any guarded API with a null argument, e.g. FileSystemAccess.execute(null, conf, executor) or createFileSystem(user, null); Check.notNullable-style guards run before any work starts and fail fast.

Common situations: A web layer derives the user from a request and forwards it without checking presence (missing doAs/user.name parameter); null Configuration produced by a broken config loader passed into execute(); unit tests calling the service with placeholder nulls.

Related errors

• Source must not be null
• Destination must not be null
• The filePath should not be null!
• {name} cannot be empty
• Job Priority cannot be null.

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/e622de753bb5894d. Report an issue: GitHub.