如何验证json到BigDecimal的位数，但只验证小数位数？

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.math.BigDecimal;
import java.util.regex.Pattern;

public class JsonBigDecimalValidator {
    private static final Pattern DECIMAL_PATTERN = Pattern.compile("^\\d+(\\.\\d{1,2})?$");

    public static boolean validateJsonBigDecimal(String jsonString, String fieldName) throws Exception {
        ObjectMapper objectMapper = new ObjectMapper();
        JsonNode jsonNode = objectMapper.readTree(jsonString);

        JsonNode fieldNode = jsonNode.get(fieldName);
        if (fieldNode == null || !fieldNode.isNumber()) {
            throw new IllegalArgumentException("Invalid JSON or field not found");
        }

        BigDecimal value = fieldNode.decimalValue();
        String decimalString = value.toString();

        return DECIMAL_PATTERN.matcher(decimalString).matches();
    }

    public static void main(String[] args) {
        String jsonString = "{\"amount\": 123.45}";

        try {
            boolean isValid = validateJsonBigDecimal(jsonString, "amount");
            System.out.println("Validation result: " + isValid);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}