didi/DoKit · error · IllegalArgumentException

Unsupported object type: " + object.getClass().getName()

Error message

Unsupported object type: " + object.getClass().getName()

What it means

The final else branch of CollectionUtils.get tries reflective java.lang.reflect.Array.get(object, index); if the object is not an array at all, Array.get throws IllegalArgumentException, which this code catches and rethrows as IllegalArgumentException('Unsupported object type: ' + className). So the input matched none of Map/List/Object[]/Iterator/Collection/Enumeration and is not a reflective array (e.g. a primitive array like int[] handled here, or a plain POJO).

Source

Thrown at Android/dokit-util/src/main/java/com/didichuxing/doraemonkit/util/CollectionUtils.java:749

        } else if (object instanceof Collection) {
            Iterator iterator = ((Collection) object).iterator();
            return get(iterator, index);
        } else if (object instanceof Enumeration) {
            Enumeration it = (Enumeration) object;
            while (it.hasMoreElements()) {
                index--;
                if (index == -1) {
                    return it.nextElement();
                } else {
                    it.nextElement();
                }
            }
            throw new IndexOutOfBoundsException("Entry does not exist: " + index);
        } else {
            try {
                return Array.get(object, index);
            } catch (IllegalArgumentException ex) {
                throw new IllegalArgumentException("Unsupported object type: " + object.getClass().getName());
            }
        }
    }

    /**
     * Gets the size of the collection/iterator specified.
     * <p>
     * This method can handles objects as follows
     * <ul>
     * <li>Collection - the collection size
     * <li>Map - the map size
     * <li>Array - the array size
     * <li>Iterator - the number of elements remaining in the iterator
     * <li>Enumeration - the number of elements remaining in the enumeration
     * </ul>
     *
     * @param object the object to get the size of
     * @return the size of the specified collection

View on GitHub (pinned to 626827cddb)

Solutions

1. Validate the container type before calling: accept only Map, List, Object[], Iterator, Collection, Enumeration or isArray() values.
2. Fix the data source so it produces the expected container type (e.g. correct JSON generic type when parsing).
3. Wrap the call in try/catch(IllegalArgumentException) and fall back to treating the object as a scalar.

Example fix

// before
Object first = CollectionUtils.get(jsonResult, 0); // throws if jsonResult is a JSONObject-like Map is fine, but a scalar throws

// after
if (jsonResult instanceof List || jsonResult instanceof Object[]
        || (jsonResult != null && jsonResult.getClass().isArray())) {
    Object first = CollectionUtils.get(jsonResult, 0);
} else {
    Object first = jsonResult; // scalar: it IS the value
}

static boolean isGettable(Object o) {
    return o instanceof Map || o instanceof List || o instanceof Collection
            || o instanceof Iterator || o instanceof Enumeration
            || o instanceof Object[] || (o != null && o.getClass().isArray());
}

static boolean isGettable(Object o) {
    return o instanceof Map || o instanceof Collection || o instanceof Iterator
            || o instanceof Enumeration || o instanceof Object[]
            || (o != null && o.getClass().isArray());
}

try { v = CollectionUtils.get(o, i); } catch (IllegalArgumentException e) { v = o instanceof List ? ((List<?>) o).get(i) : null; }

When it happens

Trigger: Calling get on a String, a POJO, an Optional, or any custom object; primitive arrays actually work via Array.get, so the throw means the object is genuinely non-array and non-container.

Common situations: Generic 'get element at index' helpers fed with boxed values after a refactor; JSON deserialization producing LinkedHashMap where a List was expected; passing a CharSequence where the code assumed a collection.

Related errors

• Not an array: " + array.getClass()
• Array has incompatible type: " + array.getClass()
• Index cannot be negative: " + index
• Entry does not exist: " + index
• precision shouldn't be less than zero!

AI-assisted analysis of didi/DoKit@626827cddb (2026-08-14). Data as JSON: /api/errors/29fa658670614f8d. Report an issue: GitHub.