chinabugotech/hutool · error · NullPointerException

PrimitiveConverter not allow null target type!

Error message

PrimitiveConverter not allow null target type!

What it means

PrimitiveConverter's constructor requires a non-null Class that is also a primitive type (byte/short/int/long/float/double/char/boolean). Passing null throws NullPointerException immediately; passing a non-primitive class throws IllegalArgumentException.

Source

Thrown at hutool-core/src/main/java/cn/hutool/core/convert/impl/PrimitiveConverter.java:40

 * 		<li>{@code boolean}</li>
 * </ul>
 *
 * @author Looly
 */
public class PrimitiveConverter extends AbstractConverter<Object> {
	private static final long serialVersionUID = 1L;

	private final Class<?> targetType;

	/**
	 * 构造<br>
	 *
	 * @param clazz 需要转换的原始
	 * @throws IllegalArgumentException 传入的转换类型非原始类型时抛出
	 */
	public PrimitiveConverter(Class<?> clazz) {
		if (null == clazz) {
			throw new NullPointerException("PrimitiveConverter not allow null target type!");
		} else if (false == clazz.isPrimitive()) {
			throw new IllegalArgumentException("[" + clazz + "] is not a primitive class!");
		}
		this.targetType = clazz;
	}

	@Override
	protected Object convertInternal(Object value) {
		return PrimitiveConverter.convert(value, this.targetType, this::convertToStr);
	}

	@Override
	protected String convertToStr(Object value) {
		return StrUtil.trim(super.convertToStr(value));
	}

	@Override
	@SuppressWarnings("unchecked")

View on GitHub (pinned to 8870454b2a)

Solutions

1. Null-check the class before constructing: Objects.requireNonNull(clazz).
2. Route through Convert / ConverterRegistry which resolves primitive vs boxed types internally.
3. Pass one of the primitive class literals (int.class, long.class, etc.) explicitly.

Example fix

// before
Converter c = new PrimitiveConverter(resolvedClass); // resolvedClass may be null

// after - guard then construct
if (resolvedClass == null || !resolvedClass.isPrimitive()) {
    throw new IllegalArgumentException("primitive class required");
}
Converter c = new PrimitiveConverter(resolvedClass);

Objects.requireNonNull(clazz, "primitive class must not be null");
if (!clazz.isPrimitive()) {
    throw new IllegalArgumentException("not a primitive class: " + clazz);
}
new PrimitiveConverter(clazz);

clazz != null && clazz.isPrimitive()

try {
    return new PrimitiveConverter(clazz);
} catch (NullPointerException e) {
    if (e.getMessage().contains("not allow null target type")) { /* resolve class first */ }
    else throw e;
}

When it happens

Trigger: Constructing new PrimitiveConverter(null), typically when the class argument was derived reflectively and resolved to null (e.g. a generic type parameter with no erasure).

Common situations: Programmatic converter construction from reflected/generic types where the resolved class can be null; copy-paste omitting the class argument.

Related errors

• [type] and [defaultValue] are both null for Converter [{}],
• Default value [{}]({}) is not the instance of [{}]
• Video URI is empty
• File not found!
• The object to build a hash code for must not be null

AI-assisted analysis of chinabugotech/hutool@8870454b2a (2026-08-14). Data as JSON: /api/errors/c257b5cb439d0e74. Report an issue: GitHub.