How to detect if a long type is actually NULL?

Question

We have a nullable (type long) column (named referral) in our MySQL database. We use hibernate for ORM.

I am trying to get the value of the column for a given member. Some are null, and if its not, its an id that points to another member whose is the referrer.

The problem is in the java code I am trying to detect if that member's column is null, if not, do something.

String referrerAffiliateId = Long.toString(member.getReferral());
if (referrerAffiliateId != null){
    //do something
}

member.getReferral() returns the value (type long) of the referral column. Some of those columns are null and some are not.

The above code compiles fine, but I get a nullPointerException when I call the method on a user whose referral column is null.

How do I properly do a detection on this?

Thanks in advance!

Full Answer:

Thanks to @Marcelo for the best correct answer.

Here is the code in its final state:

Long referrerAffiliateId = member.getReferral();
if (referrerAffiliateId != null) {
    //...
}

Answer 1

Assuming member.getReferral() returns a Long, use:

if (member.getReferral() != null)

In Hibernate, if you want to be able to detect nullability in a property, you must not use primitive types, because they will always have a default value 0 for longs.

Answer 2

The exception probably comes from Long.toString(), try checking the value before converting to a string:

Long ref = member.getReferral();
if (ref == null) {
  // Do something...
} else {
  String referrerAffiliateId = Long.toString(ref);
  // ...
}