[hibernate-dev] 5.2 Java 8 Optional support

Since 5.2 is moving to baseline on Java 8 we've been looking at Java 8 features we might leverage in Hibernate and allow users to leverage. The first one I am tackling is "support for Optional", which will have the following parts: 1. Support models which define attributes using Optional 2. Allow retrieving Objects from Hibernate as Optional The second part is really about allowing users to request that Hibernate return Optional in cases where the result may be null. This will be very targeted to cases where the user ask Hibernate to get an entity, e.g. Session#get, Session#find, *LoadAccess#load, Query#getSingleResult, Query#uniqueResult, etc. I am against adding any more overloaded Session#get methods, so I will actually limit that to *LoadAccess#load. So here I propose adding: 1. Optional<R> *LoadAccess<R>#loadOptional() 2. Optional<R> Query<R>#uniqueResultOptional() The second part is about accepting Optionals from the user. The biggest use case here is the use of Optional in the application domain model for persistent attributes. Again tis breaks down into 2 concerns: 1. Getting/setting values of such persistent attributes. 2. Appropriately marking column(s) of such persistent attributes nullable (by default, at least) The first concern initially seems like a god candidate for Types, but it really does not fit. I think the better place to deal with this is PropertyAcess and specifically the Getter and Setter it returns. The logical there being that the "type" is still the <T>, not the Optional. Handling column nullability will be a challenge given the current state of annotation binding code. Another consideration is accepting Query parameters that are Optional. It is a silly idea to pass an Optional as a parameter, I agree. But there are places it legitimately comes up: - setParameter( ..., a.getSomeOptional() ) - where getSomeOptional is an Optional - setProperties( a ) - where a is a bean that defines Optional(s) Anyway, that's the plan and I'm sticking to it (unless I hear feedback).