Checking for a null int value from a Java ResultSe

Question

In Java I'm trying to test for a null value, from a ResultSet, where the column is being cast to a primitive int type.

int iVal;
ResultSet rs = magicallyAppearingStmt.executeQuery(query);
if (rs.next()) {
  if (rs.getObject("ID_PARENT") != null && !rs.wasNull()) {
    iVal = rs.getInt("ID_PARENT");
  }
}

From the code fragment above, is there a better way to do this, and I assume that the second wasNull() test is redundant?

Educate us, and Thanks

Answer 1

I think, it is redundant. rs.getObject("ID_PARENT") should return an Integer object or null, if the column value actually was NULL. So it should even be possible to do something like:

if (rs.next()) {
  Integer idParent = (Integer) rs.getObject("ID_PARENT");
  if (idParent != null) {
    iVal = idParent; // works for Java 1.5+
  } else {
    // handle this case
  }      
}

Answer 2

The default for ResultSet.getInt when the field value is NULL is to return 0, which is also the default value for your iVal declaration. In which case your test is completely redundant.

If you actually want to do something different if the field value is NULL, I suggest:

int iVal = 0;
ResultSet rs = magicallyAppearingStmt.executeQuery(query);
if (rs.next()) {
    iVal = rs.getInt("ID_PARENT");
    if (rs.wasNull()) {
        // handle NULL field value
    }
}

(Edited as @martin comments below; the OP code as written would not compile because iVal is not initialised)

Answer 3

Just check if the field is null or not using ResultSet#getObject(). Substitute -1 with whatever null-case value you want.

int foo = resultSet.getObject("foo") != null ? resultSet.getInt("foo") : -1;

Or, if you can guarantee that you use the right DB column type so that ResultSet#getObject() really returns an Integer (and thus not Long, Short or Byte), then you can also just typecast it to an Integer.

Integer foo = (Integer) resultSet.getObject("foo");