PMD: how to deal with no need to check null before instanceof

Question

Hi i have the following code.

if (SecurityContextHolder.getContext().getAuthentication() != null
                && SecurityContextHolder.getContext().getAuthentication()
                        .getPrincipal() instanceof User)

When I check with pmd it is giving me an warning: No need to check null before instanceof.

Q1.) How do you fix this warning? -- if i just do security SecurityContextHolder.getContext().getAuthentication().getPrincipal() and getAuthentication is null than I would get NPE (Null pointer exception).

You might want to look at http://stackoverflow.com/questions/2950319/is-null-check-needed-before-calling-instanceof: if the value is null, `instanceof` returns `false`. — tonio, May 02 '12 at 13:38
Tonio, you might want to re-read the question. He can't safely get the value without checking an intermediate result for null. — Chris Morley, May 07 '12 at 18:41

score 2 · Answer 1 · answered May 03 '12 at 12:32

2

I think this is a bug in PMD because I face the same problem. Maybe the XPath Expression for this pattern is not clear enough. But it is already fixed. See http://sourceforge.net/tracker/index.php?func=detail&aid=2317099&group_id=56262&atid=479921

answered May 03 '12 at 12:32

ambassador86

161
1
5

score 1 · Accepted Answer · answered May 07 '12 at 18:44

If you can't use the fixed version of PMD, add a temporary variable

... principal = null;
if (SecurityContextHolder.getContext().getAuthentication() != null)
   principal = SecurityContextHolder.getContext().getAuthentication()
                    .getPrincipal();
if (principal instanceof User) ...

PMD: how to deal with no need to check null before instanceof

2 Answers2