What causes "Json object ended without }" in quarkusio/quarkus?

Validate the JSON document and add the missing '}' at the position indicated by the parser

quarkusio/quarkus · error · IllegalArgumentException

Json object ended without }

Error message

Json object ended without }

What it means

While parsing a JSON object, readObject() consumes members inside '{' ... '}'. If the input is exhausted (end of text) before a closing '}' is found, the object is unbalanced and the reader throws IllegalArgumentException. It indicates a missing brace in the JSON document.

Source

Thrown at independent-projects/bootstrap/json/src/main/java/io/quarkus/bootstrap/json/JsonReader.java:109

        Map<JsonString, JsonValue> members = new HashMap<>();

        while (position < length) {
            ignoreWhitespace();
            switch (peekChar()) {
                case '}':
                    position++;
                    return new JsonObject(members);
                case ',':
                    position++;
                    break;
                case '"':
                    readMember(members);
                    break;
            }
        }

        throw new IllegalArgumentException("Json object ended without }");
    }

    /**
     * member
     * |----- ws string ws ':' element
     */
    private void readMember(Map<JsonString, JsonValue> members) {
        final JsonString attribute = readString();
        ignoreWhitespace();
        final int colon = nextChar();
        if (':' != colon) {
            throw new IllegalArgumentException("Expected : after attribute");
        }
        final JsonValue element = readElement();
        members.put(attribute, element);
    }

    /**

View on GitHub (pinned to e1c734241f)

Solutions

Validate the JSON document and add the missing '}' at the position indicated by the parser
If generating JSON by string concatenation, switch to a builder/serializer that guarantees balanced braces
Check for truncation in the transport layer (file read limits, buffer sizes, HTTP body length)

Example fix

// before
String json = "{\"a\": 1";
// after
String json = "{\"a\": 1}";

Defensive patterns

Strategy: try-catch

Validate before calling

long opens = jsonText.chars().filter(c -> c == '{').count();
long closes = jsonText.chars().filter(c -> c == '}').count();
if (opens != closes) {
    throw new IllegalArgumentException("Unbalanced braces in JSON input");
}

Try / catch

try {
    JsonValue v = new JsonReader(text).read();
} catch (IllegalArgumentException e) {
    if (e.getMessage().equals("Json object ended without }")) {
        // treat input as truncated/malformed: log and re-fetch or repair
    }
}

Prevention

Prefer a JSON builder/serializer over string concatenation for generating JSON
Validate generated JSON at the producer side before transport
Watch for truncation in streaming or size-limited transports

When it happens

Trigger: A JSON object literal that is never closed, e.g. '{"a": 1' with no '}', or truncation in the middle of a nested object.

Common situations: Manually building JSON strings via string concatenation and missing the final brace; truncated network payloads; template-generated JSON with a conditionally dropped '}'.

Related errors

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/1cc45cfc5b2e6091. Report an issue: GitHub.