@Override
    public String toString() {
        final StringBuilder sb = new StringBuilder("Struct{");
        boolean first = true;
        for (int i = 0; i < values.length; i++) {
            final Object value = values[i];
            if (value != null) {
                final Field field = schema.fields().get(i);
                if (first) {
                    first = false;
                } else {
                    sb.append(",");
                }
                sb.append(field.name()).append("=").append(value);
            }
        }
        return sb.append("}").toString();
    }
Validates that this struct has filled in all the necessary data with valid values. For required fields
without defaults, this validates that a value has been set and has matching types/schemas. If any validation
fails, throws a {@link DataException}.
connect/api/src/main/java/org/apache/kafka/connect/data/Struct.java