google/gson · error · JsonSyntaxException

Failed parsing '${s}' as BigDecimal; at path ${path}

Error message

Failed parsing '${s}' as BigDecimal; at path ${path}

What it means

The BIG_DECIMAL adapter reads a JSON token as a string and passes it to NumberLimits.parseBigDecimal. If the string is not a valid BigDecimal representation, or exceeds the number-string-length or scale limits enforced by NumberLimits, the NumberFormatException is wrapped in a JsonSyntaxException with the offending value and path.

Source

Thrown at gson/src/main/java/com/google/gson/internal/bind/TypeAdapters.java:593

        @Override
        public void write(JsonWriter out, String value) throws IOException {
          out.value(value);
        }
      };

  public static final TypeAdapter<BigDecimal> BIG_DECIMAL =
      new TypeAdapter<BigDecimal>() {
        @Override
        public BigDecimal read(JsonReader in) throws IOException {
          if (in.peek() == JsonToken.NULL) {
            in.nextNull();
            return null;
          }
          String s = in.nextString();
          try {
            return NumberLimits.parseBigDecimal(s);
          } catch (NumberFormatException e) {
            throw new JsonSyntaxException(
                "Failed parsing '" + s + "' as BigDecimal; at path " + in.getPreviousPath(), e);
          }
        }

        @Override
        public void write(JsonWriter out, BigDecimal value) throws IOException {
          out.value(value);
        }
      };

  public static final TypeAdapterFactory BIG_DECIMAL_FACTORY =
      newFactory(BigDecimal.class, BIG_DECIMAL);

  public static final TypeAdapter<BigInteger> BIG_INTEGER =
      new TypeAdapter<BigInteger>() {
        @Override
        public BigInteger read(JsonReader in) throws IOException {
          if (in.peek() == JsonToken.NULL) {

View on GitHub (pinned to 310ac341f2)

Solutions

1. Validate that the JSON value is a well-formed decimal number before deserializing into BigDecimal
2. If the value can be non-numeric, use String as the field type and convert to BigDecimal separately
3. For known oversized inputs, register a custom TypeAdapter that pre-checks or truncates

Example fix

// before
class Product { BigDecimal price; }
gson.fromJson("{\"price\":\"N/A\"}", Product.class); // throws

// after
class Product { String price; // parse to BigDecimal after validation
  BigDecimal priceValue() { return new BigDecimal(price); }
}

// Validate that a string is a parseable BigDecimal before deserializing
public static boolean isValidBigDecimal(String s) {
    try {
        NumberLimits.parseBigDecimal(s);
        return true;
    } catch (NumberFormatException e) {
        return false;
    }
}

try {
    Product p = gson.fromJson(json, Product.class);
} catch (JsonSyntaxException e) {
    if (e.getMessage().contains("Failed parsing") && e.getMessage().contains("BigDecimal")) {
        // use a String field and parse manually with error handling
    }
}

When it happens

Trigger: Deserialifying a JSON value like "abc" or "1.2.3" or an excessively long number string into a BigDecimal field.

Common situations: Malformed numeric strings from an API; mixed-type fields that sometimes contain non-numeric text; a value with a scale exceeding 10,000 digits (a NumberLimits guard against DoS via oversized numbers).

Related errors

• Failed parsing '${s}' as Date; at path ${path}
• Expecting number, got: ${jsonToken}; at path ${path}
• Invalid bitset value ${intValue}, expected 0 or 1; at path $
• Lossy conversion from ${intValue} to byte; at path ${path}
• Lossy conversion from ${intValue} to short; at path ${path}

AI-assisted analysis of google/gson@310ac341f2 (2026-08-10). Data as JSON: /api/errors/1dc2de46477e40a4. Report an issue: GitHub.