[Hawkular-dev] @Null / @NotNull

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