java.lang.ClassNotFoundException: org.hibernate.engine.spi.SharedSessionContractImplementor

[johnou]

After updating to jackson-datatype-hibernate 2.9.7 (Hibernate 5.1.7 on the classpath) I found that PersistentCollectionSerializer cannot be instantiated when trying to register the module due to a cnfe..

import com.fasterxml.jackson.datatype.hibernate5.PersistentCollectionSerializer;

public class Main {

    public static void main(String[] args) {
        new PersistentCollectionSerializer(null, null, 0, null);
    }
}

Exception in thread "main" java.lang.NoClassDefFoundError: org/hibernate/engine/spi/SharedSessionContractImplementor
	at Main.main(Main.java:8)
Caused by: java.lang.ClassNotFoundException: org.hibernate.engine.spi.SharedSessionContractImplementor
	at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	... 1 more

[cowtowncoder]

I think that there is fundamental incompatibility between various "minor" Hibernate versions, so that it is not possible for this module to work against 5.0, 5.1 AND 5.2. I forget what were the trade-offs, but I think this problem would go away with Hibernate 5.2 or higher.

[johnou]

@cowtowncoder what's peculiar is that I cannot see where org.hibernate.engine.spi.SharedSessionContractImplementor is referenced..

[cowtowncoder]

Perhaps it is referenced indirectly... although that would be bit odd, would expect that not to happen without module somehow referencing it.

[johnou]

@cowtowncoder I was able to "fix" this by checking out the 2.9.7 tag and changing the Hibernate version to 5.1.17.Final and using that artifact. Only possible workaround I can think of is to introduce a new module for every major version eg. hibernate5 hibernate52 hibernate53

[cowtowncoder]

Yes, I think that was the conclusion. One small thing that might be helpful would be to at least document which versions of Hibernate module is compatible with -- to me the least bad option would seem to be to try to support as many of the latest 5.x (5.4, 5.3, if possible 5.2....) as possible.

One critical short-coming is that this module does not have active maintainer. If there was one, that person could both figure out contraints and make decisions. Problem for me is that I will try to help as I can, but I do not use Hibernate myself and am not familiar with its internals (to the degree I could fully own this module). Module was added as a contribution, and is clearly useful, so I feel bad for it being bit of an oprhan.

So, if you or anyone else interested and passionate enough wanted to look into things, I would be happy to give more access and authority -- this would be great for users. And I think it is something that could be valuable for the new owner: doing important and quite visible OSS work that benefits many.
So far there are about half a dozen Jackson modules for which I am not the lead (or am not the only lead), and I'd love Hibernate datatype module to become one more.

That being said, I appreciate your reaching out and helping by sharing work-around you have found, additional information. That is helpful as well.