apache/hadoop · error · HadoopIllegalArgumentException

null component type not allowed

Error message

null component type not allowed

What it means

ArrayPrimitiveWritable wraps a Java array of primitives (boolean, char, byte, short, int, long, float, double) for Writable serialization. checkPrimitive() rejects a null componentType before the instance can be built. This is thrown when the componentType argument passed to ArrayPrimitiveWritable(Class<?>) is null, since the value-carrying paths (set()) run checkArray() first and never reach here with null.

Source

Thrown at hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/ArrayPrimitiveWritable.java:73

    new HashMap<String, Class<?>>(16);
  static {
    PRIMITIVE_NAMES.put(boolean.class.getName(), boolean.class);
    PRIMITIVE_NAMES.put(byte.class.getName(), byte.class);
    PRIMITIVE_NAMES.put(char.class.getName(), char.class);
    PRIMITIVE_NAMES.put(short.class.getName(), short.class);
    PRIMITIVE_NAMES.put(int.class.getName(), int.class);
    PRIMITIVE_NAMES.put(long.class.getName(), long.class);
    PRIMITIVE_NAMES.put(float.class.getName(), float.class);
    PRIMITIVE_NAMES.put(double.class.getName(), double.class);
  }
  
  private static Class<?> getPrimitiveClass(String className) {
    return PRIMITIVE_NAMES.get(className);
  }
  
  private static void checkPrimitive(Class<?> componentType) {
    if (componentType == null) { 
      throw new HadoopIllegalArgumentException("null component type not allowed"); 
    }
    if (! PRIMITIVE_NAMES.containsKey(componentType.getName())) {
      throw new HadoopIllegalArgumentException("input array component type "
          + componentType.getName() + " is not a candidate primitive type");
    }
  }
  
  private void checkDeclaredComponentType(Class<?> componentType) {
    if ((declaredComponentType != null) 
        && (componentType != declaredComponentType)) {
      throw new HadoopIllegalArgumentException("input array component type "
          + componentType.getName() + " does not match declared type "
          + declaredComponentType.getName());     
    }
  }
  
  private static void checkArray(Object value) {
    if (value == null) { 

View on GitHub (pinned to 2add963021)

Solutions

1. Pass one of the eight primitive TYPE constants (Integer.TYPE, Long.TYPE, Boolean.TYPE, Character.TYPE, Byte.TYPE, Short.TYPE, Float.TYPE, Double.TYPE) instead of null.
2. If the Class comes from a lookup, null-check it before constructing and fail with your own descriptive error naming the offending input.
3. Use the no-arg ArrayPrimitiveWritable() plus set(Object) if you only have a value, so the component type is derived from a real array.

Example fix

// before
Class<?> t = PRIMITIVES.get(configuredType); // may be null
new ArrayPrimitiveWritable(t);

// after
Class<?> t = PRIMITIVES.get(configuredType);
if (t == null) {
  throw new IllegalArgumentException("Unknown primitive type: " + configuredType);
}
new ArrayPrimitiveWritable(t);

Class<?> t = resolveComponentType(cfg);
if (t == null || !t.isPrimitive()) {
  throw new IllegalArgumentException("Component type must be a primitive, got: " + cfg);
}

When it happens

Trigger: Calling new ArrayPrimitiveWritable((Class<?>) null) — the constructor at line 113 passes the argument straight into checkPrimitive(). Also any subclass or reflection-based call that supplies a null Class to this constructor.

Common situations: Programmatically building a component type from configuration or a schema (e.g. Class.forName(userType) returning null being swallowed, or a map lookup miss) and passing the result into the typed constructor.

Related errors

• null value not allowed
• null valueClass
• source map cannot be null
• input array component type {} does not match declared type {
• The EnumSet argument is null, or is an empty set but with no

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/15ed209501b6b593. Report an issue: GitHub.