[Hawkular-dev] @Null / @NotNull

[Michael Burman]

Hi,

This is actually very good read about Optional benefits (with lambdas especially): http://vanillajava.blogspot.fi/2015/01/java-8-optional-is-not-just-for.html

Then again, I hope we don't start to use Optional when something really isn't optional. That kills readability.

  -  Micke

----- Original Message -----
From: "John Sanda" <jsanda at redhat.com>
To: hawkular-dev at lists.jboss.org
Sent: Monday, 2 March, 2015 2:54:28 PM
Subject: Re: [Hawkular-dev] @Null / @NotNull

How about using the Optional class introduced in Java instead of null? Not only does it provide documentation like the annotations do, but Optional also provides a rich API that the annotations do not. If you are not familiar with Optional, this article[1] is a good overview. 

[1] http://www.oracle.com/technetwork/articles/java/java8-optional-2175753.html 




On Mar 2, 2015, at 5:27 AM, Heiko W.Rupp < hrupp at redhat.com > wrote: 

Hey, 

as we were having a discussion this morning on #hawkular-dev about null 

I think we should start (on top of writing more JavaDoc) using 
annotations to mark methods and method parameters that 
allow being null / not null and if they may return null or not. 

This is especially important on API classes(*1), that may be 
consumed by 3rd parties that may or may not have insight 
into source of the implementation (on top of that, such annotations 
are an enhancement of the API contract). 

I know we have been talking about that in the past without 
no real result. Luckily since then JSR 308 has been 
marked as final and thus a standard exists, that includes such 
annotations (+ a checking framework, + tooling to retroactively add 
such annotations to existing source). 

See http://types.cs.washington.edu/checker-framework/ 
and http://mvnrepository.com/artifact/org.checkerframework for mvn artifacts 

http://mvnrepository.com/artifact/org.checkerframework/checker-qual/1.8.10 <- annotations 
http://types.cs.washington.edu/checker-framework/current/api/ <- Javadoc 

Another option are the org.jetbrains versions of the annotations, which are around for a while. 

If we only care about documentation, but not compile time and/or static analysis, we can also 
use the ones from BeanValidation, which live under the javax package spaces (iirc). *2 

Here is a more complete list of frameworks 
http://stackoverflow.com/questions/4963300/which-notnull-java-annotation-should-i-use 




*1) Java and REST 
*2) BV may be a good idea for more complex input like in alert definition 




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