spring 2.0 findbugs nullable throws error even when wrapped in null check

Question

I'm having difficulty with Findbugs complaining about springs HttpEntity.getBody().

Below you'll see I call response.getBody().length, which I understand could cause a NPE. However when I wrap it in if (response.getBody() != null), it still complains. It only does this in Spring 2.0 (not 1.5) which appears to be related to the @Nullable annotation added to the method.

Can I get an explanation why even when I wrap it in a null check, it still complains when I get the length of it?

Bug type NP_NULL_ON_SOME_PATH_FROM_RETURN_VALUE

ResponseEntity<SomeClass[]> response = restTemplate.exchange(someUrl, HttpMethod.GET, httpEntity,
                SomeClass[].class);
for (int i = 0; response.getBody().length > i;   i++) {
                        doSomething()
                    }

Answer 1

According to Spot bugs documentation the reason for this occuring is :

'The return value from a method is dereferenced without a null check, and the return value of that method is one that should generally be checked for null. This may lead to a NullPointerException when the code is executed.'

fixed it by:

Optional <T> body = Optional.ofNullable(response.getBody);
if (body.isPresent()) {
   //use body
}

You are getting the warning because getBody method has been annotated as Nullable and spotBugs / findbugz expects that an explicit null checker be made before using the value. Works well for me.