Activiti/Activiti · error · JSONException

JSONObject[" + quote(key) + "] is not a JSONArray.

Error message

JSONObject[" + quote(key) + "] is not a JSONArray.

What it means

Thrown by JSONObject.getJSONArray when the value stored under the requested key exists but is not a JSONArray (or the key is missing), so the typed access is impossible — a JSON type mismatch rather than a syntax error.

Solutions

  1. Check opt(key) instanceof JSONArray before casting; wrap a lone non-array value into a new JSONArray if you want tolerant reading.
  2. Use a helper that normalizes 'object or array' fields to a list.
  3. Fix the producer so the field is always an array.
  4. Wrap in try-catch (JSONException) and treat as empty list.

Example fix

// before
JSONArray list = config.getJSONArray("variables");
// after
Object o = config.opt("variables");
JSONArray list;
if (o instanceof JSONArray) {
    list = (JSONArray) o;
} else if (o != null) {
    list = new JSONArray().put(o);
} else {
    list = new JSONArray();
}
Defensive patterns

Strategy: type-guard

Validate before calling

Object o = obj.opt(key); boolean ok = o instanceof JSONArray;

Type guard

JSONArray arrayOrWrapped(JSONObject obj, String key) { Object o = obj.opt(key); if (o instanceof JSONArray) return (JSONArray) o; if (o != null) return new JSONArray().put(o); return new JSONArray(); }

Try / catch

try { JSONArray a = obj.getJSONArray(key); } catch (JSONException e) { a = new JSONArray(); }

Prevention

When it happens

Trigger: Calling getJSONArray(key) where the stored value is a scalar, JSONObject, or JSONObject.NULL — e.g. a field that was a list in one payload version but a single object/string in another.

Common situations: JSON APIs that collapse single-element collections to a bare object; schema drift between process engine versions reading job/variable configuration; typo'd keys pointing at scalar fields.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

AI-assisted analysis of Activiti/Activiti@56435b1a97 (2026-09-09). Data as JSON: /api/errors/4425158dd41d6e30. Report an issue: GitHub.

Appendix: source

Thrown at activiti-core/activiti-engine/src/main/java/org/activiti/engine/impl/util/json/JSONObject.java:452

            throw new JSONException("JSONObject[" + quote(key) + "] is not an int.");
        }
    }

    /**
     * Get the JSONArray value associated with a key.
     *
     * @param key
     *          A key string.
     * @return A JSONArray which is the value.
     * @throws JSONException
     *           if the key is not found or if the value is not a JSONArray.
     */
    public JSONArray getJSONArray(String key) throws JSONException {
        Object o = get(key);
        if (o instanceof JSONArray) {
            return (JSONArray) o;
        }
        throw new JSONException("JSONObject[" + quote(key) + "] is not a JSONArray.");
    }

    /**
     * Get the JSONObject value associated with a key.
     *
     * @param key
     *          A key string.
     * @return A JSONObject which is the value.
     * @throws JSONException
     *           if the key is not found or if the value is not a JSONObject.
     */
    public JSONObject getJSONObject(String key) throws JSONException {
        Object o = get(key);
        if (o instanceof JSONObject) {
            return (JSONObject) o;
        }
        throw new JSONException("JSONObject[" + quote(key) + "] is not a JSONObject.");
    }

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