Consider upgrade to Hibernate ORM 5.2

[Polve]

Hibernate 5.2 is now GA and it might be nice to upgrade as part of Spring Boot 1.4.

[philwebb]

A lot of things have changed between 5.1 and 5.2 (Java 8 minimum requirement being the most concerning). Ideally it would be good to get this into Spring Boot 1.4 as people will be upgrading from Hibernate 4.x and it would be nice to get all the pain out of the way in one hit.

[rakpan]

Are we raising the bar for spring boot too?

[philwebb]

@rakpan Not until Spring Boot 2.0. However, we could still consider Hibernate 5.2 as our default choice as long as people can easily downgrade.

[snicoll]

Considering that hibernate-entitymanager is gone in 5.2, switching to 5.2 effectively means that 5.2 is our bare minimum since it changes the pom structure. I'd argue 5.2.1 should restore that artifact (even if it's empty) for backward compatible reason.

@philwebb I had a quick look and the "as long as people can easily downgrade" does not seem possible at the moment.

I've raised HHH-10823

[philwebb]

@snicoll Unless I'm missing something, I'm not sure I agree. Users might not be able to downgrade with a single property but they could set the property and add back hibernate-entitymanager.

[snicoll]

Yes. I don't consider that as "easy".

[philwebb]

@snicoll It's not super easy, but it's not that hard and it's probably less confusing that having an empty hibernate-entitymanager project that doesn't contain anything.

My approach to use hibernate 5.2 right now would be

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
        <exclusions>
            <exclusion>
                <groupId>org.hibernate</groupId>
                <artifactId>hibernate-entitymanager</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>

[wilkinsona]

Spring Framework 4.3.0.RELEASE isn't fully compatible with Hibernate 5.1 (see SPR-14365) so we either need to move to 5.2 or wait for Spring Framework 4.3.1.RELEASE.