apache/dubbo · error · IllegalArgumentException

value '%s' for key '%s' in '%s' is not a number

Error message

value '%s' for key '%s' in '%s' is not a number

What it means

Thrown by AbstractJsonUtilImpl.getNumberAsDouble(Map,String) when obj contains key but the value is neither a Double nor a String — i.e. it is a Long, Integer, Boolean, List, Map, or any other type the method does not handle. The method only accepts Double or parseable String; other numeric boxed types (Long/Integer) are NOT auto-promoted and fall through to this terminal IllegalArgumentException naming the value, key, and the whole object.

Source

Thrown at dubbo-common/src/main/java/org/apache/dubbo/common/json/impl/AbstractJsonUtilImpl.java:133

    public Double getNumberAsDouble(Map<String, ?> obj, String key) {
        assert obj != null;
        assert key != null;
        if (!obj.containsKey(key)) {
            return null;
        }
        Object value = obj.get(key);
        if (value instanceof Double) {
            return (Double) value;
        }
        if (value instanceof String) {
            try {
                return Double.parseDouble((String) value);
            } catch (NumberFormatException e) {
                throw new IllegalArgumentException(
                        String.format("value '%s' for key '%s' is not a double", value, key));
            }
        }
        throw new IllegalArgumentException(
                String.format("value '%s' for key '%s' in '%s' is not a number", value, key, obj));
    }

    /**
     * Gets a number from an object for the given key, casted to an integer.  If the key is not
     * present, this returns null.  If the value does not represent an integer, throws an exception.
     */
    @Override
    public Integer getNumberAsInteger(Map<String, ?> obj, String key) {
        assert obj != null;
        assert key != null;
        if (!obj.containsKey(key)) {
            return null;
        }
        Object value = obj.get(key);
        if (value instanceof Double) {
            Double d = (Double) value;
            int i = d.intValue();

View on GitHub (pinned to 3a3043227f)

Solutions

  1. Normalize the value to Double before calling: handle Long/Integer/Number via ((Number) value).doubleValue().
  2. Use a different accessor that accepts any Number, or widen getNumberAsDouble's contract with a pre-check.
  3. Align the JSON deserializer so numeric fields decode to Double consistently.
  4. Catch IllegalArgumentException and report the offending key/type for triage.

Example fix

// before
Double v = jsonUtil.getNumberAsDouble(obj, "count"); // value is Long 5
// after - promote any Number
Object raw = obj.get("count");
Double v = raw instanceof Number ? ((Number) raw).doubleValue() : jsonUtil.getNumberAsDouble(obj, "count");
Defensive patterns

Strategy: type-guard

Validate before calling

Object raw = obj.get(key);
if (raw instanceof Number && !(raw instanceof Double)) {
    return ((Number) raw).doubleValue(); // promote Long/Integer/etc.
}
return jsonUtil.getNumberAsDouble(obj, key);

Type guard

private static boolean isDoubleOrString(Object value) {
    return value instanceof Double || value instanceof String;
}

Try / catch

try {
    return jsonUtil.getNumberAsDouble(obj, key);
} catch (IllegalArgumentException e) {
    Object raw = obj.get(key);
    if (raw instanceof Number) return ((Number) raw).doubleValue(); // recover from Long/Integer
    throw e;
}

Prevention

When it happens

Trigger: jsonUtil.getNumberAsDouble(obj, key) where obj.get(key) is a Long, Integer, Float, BigDecimal, Boolean, List, or Map. Common case: JSON deserializers that produce Long/Integer for whole-number fields, or a field holding a nested object/array where a number was expected.

Common situations: Switching JSON backends that emit Long/Integer/BigInteger where the previous backend emitted Double; whole-number JSON values parsed into Long by a stricter parser; a field that is sometimes a number and sometimes a sub-object; misconfigured mapping that bound a number field to a generic Object.

Related errors

AI-assisted analysis of apache/dubbo@3a3043227f (2026-08-14). Data as JSON: /api/errors/bd5243529302da20. Report an issue: GitHub.