apache/dubbo · error · IllegalArgumentException

object is null

Error message

object is null

What it means

Thrown by ReflectUtils.getFieldValue(Object, String) when the obj argument is null. The method uses reflection to read a declared field by name from the object's class, so a null target has no class to reflect on. This is a precondition violation — the method explicitly guards against null before attempting any field access.

Source

Thrown at dubbo-common/src/main/java/org/apache/dubbo/common/utils/ReflectUtils.java:1385

    public static Set<String> getAllFieldNames(Class<?> type) {

        Set<String> fieldNames = new HashSet<>();
        for (Field field : type.getDeclaredFields()) {
            fieldNames.add(field.getName());
        }

        Set<Class<?>> allSuperClasses = ClassUtils.getAllSuperClasses(type);
        for (Class<?> aClass : allSuperClasses) {
            for (Field field : aClass.getDeclaredFields()) {
                fieldNames.add(field.getName());
            }
        }
        return fieldNames;
    }

    public static <T> T getFieldValue(Object obj, String fieldName) throws RuntimeException {
        if (obj == null) {
            throw new IllegalArgumentException("object is null");
        }
        try {
            Field field = obj.getClass().getDeclaredField(fieldName);
            field.setAccessible(true);
            return (T) field.get(obj);
        } catch (Exception e) {
            throw new RuntimeException(e.getMessage(), e);
        }
    }
}

View on GitHub (pinned to 3a3043227f)

Solutions

1. Null-check the object before calling getFieldValue: if (obj != null) { ReflectUtils.getFieldValue(obj, name); }
2. Trace where the null originated — inspect the upstream lookup (Map, cache, or bean wiring) that produced the value.
3. If the field may legitimately be absent, catch RuntimeException and inspect the cause for NoSuchFieldException.

Example fix

// before
Object val = ReflectUtils.getFieldValue(maybeNullObj, "fieldName");

// after
if (maybeNullObj == null) {
    return null; // or throw a domain-specific exception
}
Object val = ReflectUtils.getFieldValue(maybeNullObj, "fieldName");

if (obj == null) {
    // skip or throw domain-specific exception
    return;
}
Object val = ReflectUtils.getFieldValue(obj, fieldName);

When it happens

Trigger: Calling ReflectUtils.getFieldValue(null, "fieldName") or passing a variable that evaluated to null as the first argument. Common when the caller obtained the object from a Map.get(), optional, or service lookup that returned null and did not check.

Common situations: Deserializing or inspecting an object whose source (e.g. a cached value, RPC response, or Spring bean) was not populated; test helpers that pass a mock that returned null; refactoring that changed a factory method to return null on missing data.

Related errors

• unable to determine bean class from factory's superclass or
• create bean instance failed, type=${className}
• Expect only one but found ${size} matched constructors for t
• None matched constructor was found for type: ${type}
• class == null

AI-assisted analysis of apache/dubbo@3a3043227f (2026-08-14). Data as JSON: /api/errors/720f5754dd38e755. Report an issue: GitHub.