HHH-13020 - When proxying an entity having a private default constructor, the log message is not very clear about the problem

[vladmihalcea]

https://hibernate.atlassian.net/browse/HHH-13020

[raphw]

I would actually also substitute proxyClass.newInstance() by proxyClass.getConstructor().newInstance(). The former method is deprecated as of Java 9 as it does not throw all reflection-related exceptions correctly. Looks good otherwise.

[vladmihalcea]

@raphw Good tip. Should we use proxyClass.getConstructor() or proxyClass.getDeclaredConstructor()> Is it that the Proxy class always created a public constructor or does it copy the target class constructor visibility?

[raphw]

Since we do not attempt accessibility, getConstructor is fine. It requires fewer security manager privileges, too.

I think Byte Buddyis already configured to making the constructor public anyways.

[raphw]

It does, I remembered correctly: https://github.com/hibernate/hibernate-orm/blob/e2c6fb5ed4c1f9efc677442944683251f36f93ce/hibernate-core/src/main/java/org/hibernate/proxy/pojo/bytebuddy/ByteBuddyProxyHelper.java#L57

[gsmet]

@vladmihalcea I added some guidance about how to simplify the log thingy.

Let me know if you have any question.

[gsmet]

This looks a bit overcomplicated.

I would do that this way:

catch (NoSuchMethodException e) {
    throw LOG.bytecodeEnhancementFailedBecauseOfDefaultConstructor( entityName, t )
}
catch (Throwable t) {
   throw LOG.bytecodeEnhancementFailed( entityName, t );
}

with the log methods being defined by, for instance:

@Message(value = "Bytecode enhancement failed because no public, protected or package-private default constructor was found for entity: %s. Private constructors don't work with runtime proxies!", id = 143)
HibernateException bytecodeEnhancementFailedBecauseOfDefaultConstructor(String entityName, @Cause Exception e);

JBoss-logging is very powerful, let's unleash its power!

[vladmihalcea]

@gsmet I'll try to apply your suggestion.

[vladmihalcea]

@gsmet If we skip the log as you suggest, then the log message will look like this:

INFO DefaultLoadEventListener:132 - HHH000327: Error performing load command : org.hibernate.HibernateException: HHH000143: Bytecode enhancement failed because no public, protected or package-private default constructor was found for entity: org.hibernate.jpa.test.callbacks.PrivateConstructorTest$Parent. Private constructors don't work with runtime proxies!

I think it's better to have a separate error log entry as before as it makes it more clear what happened.

[gsmet]

Two things:

• as for the first error, I see how the way it is done would lead to this situation: we need to resolve the constructor in postInstantiate(). This way you will have the error once and for all when getting the constructor and you can use the pattern I mentioned.
• you can then revert the change you made to the error handling in getProxy() and keep it as it was.

As much as possible, we need to avoid the reflection calls at runtime.

Sorry for not seeing it right away.

[gsmet]

FWIW, I'm working on it.

[vladmihalcea]

@raphw Thanks, Rafael. I applied your suggestions and will push it.