Activiti/Activiti · error · JSONException

Value out of sequence.

Error message

Value out of sequence.

What it means

JSONWriter tracks nesting state via a mode flag ('i' initial, 'o' object value pending, 'a' array element, 'k' key expected, 'd' done). append() only accepts writes in modes 'o' or 'a'; anything else throws "Value out of sequence." This is a state-machine violation: you tried to emit a value where the grammar forbids it.

Solutions

1. Call key("...") before every value() while inside an object
2. Balance every array()/object() with endArray()/endObject() before emitting further values
3. Do not reuse a JSONWriter after the document is complete; create a new instance
4. Centralize writing in small helper methods (writeKey/writeValue) that enforce the key-then-value ordering

Example fix

// before
writer.object().value(42); // value before key -> out of sequence
// after
writer.object().key("answer").value(42).endObject();

// assert a key is expected before any value() while in an object:
if (inObject && !lastCallWasKey) throw new IllegalStateException("call key() before value()");

null

try { writer.value(v); } catch (JSONException e) { if ("Value out of sequence.".equals(e.getMessage())) { /* fix call ordering: key() first inside objects */ } throw e; }

When it happens

Trigger: Calling value(...) right after object() (a key is required first), calling value() twice for one key, calling value() after endObject()/endArray() closed the document, or value() at top level after array() without array element ordering.

Common situations: Hand-rolled serialization code that forgets key() before a value in an object; missing endObject()/endArray() calls in conditional branches leaving the writer in the wrong mode; reusing a finished JSONWriter for a second document.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

• Misplaced array.
• Misplaced key.
• Misplaced object.
• Bad value from toJSONString: " + o
• e

AI-assisted analysis of Activiti/Activiti@56435b1a97 (2026-09-09). Data as JSON: /api/errors/523eacbcadee1895. Report an issue: GitHub.

Appendix: source

Thrown at activiti-core/activiti-engine/src/main/java/org/activiti/engine/impl/util/json/JSONWriter.java:139

        if (s == null) {
            throw new JSONException("Null pointer");
        }
        if (this.mode == 'o' || this.mode == 'a') {
            try {
                if (this.comma && this.mode == 'a') {
                    this.writer.write(',');
                }
                this.writer.write(s);
            } catch (IOException e) {
                throw new JSONException(e);
            }
            if (this.mode == 'o') {
                this.mode = 'k';
            }
            this.comma = true;
            return this;
        }
        throw new JSONException("Value out of sequence.");
    }

    /**
     * Begin appending a new array. All values until the balancing <code>endArray</code> will be appended to this array. The <code>endArray</code> method must be called to mark the array's end.
     *
     * @return this
     * @throws JSONException
     *           If the nesting is too deep, or if the object is started in the wrong place (for example as a key or after the end of the outermost array or object).
     */
    public JSONWriter array() throws JSONException {
        if (this.mode == 'i' || this.mode == 'o' || this.mode == 'a') {
            this.push(null);
            this.append("[");
            this.comma = false;
            return this;
        }
        throw new JSONException("Misplaced array.");
    }

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