I am profiling an application built on top of Hibernate. The profile tool is OptimizeIt.

The application appears to create a lot of classes of the form:

com.acme.model.company.Company$$ProxiedByCGLIB$$64
com.acme.model.company.Company$$ProxiedByCGLIB$$65
com.acme.model.company.Company$$ProxiedByCGLIB$$72

...and there is only ever one instance of each of these classes.

Under heavy load, the VM created more than a thousand such class definitions in a 24 hour period. I presume this behavior is related to Hibernate 'wrapping' domain classes to give them persistent behavior.

I can understand that if I have 24 (persistent) domain classes in my application, that there should be 24 Hibernate 'wrapper' counterparts. Why are there so many duplicate 'wrapper' classes for each domain class; and only ever one instance of those wrappers? This behavior seems really inefficient.

Any advice?

Thanks in advance,

Dayle


dayle.woolston@nextpage.com

This is incorrect. Hibernate can persist your objects without any wrappers (well, except for collections). It actually relates to you defining proxies in your mapping. CGLIB is the library Hibernate uses to generate dynamic proxies in order to implement lazy loading.

You could turn off proxying if you really want to, but just wait till you see the amount of garbage created by your jdbc driver.

Those particular classes are method proxies, and there will be one created for each method of every class that is proxied. There is some overhead to create these but it will only happen the first time the class is used, and they speed up the actual execution of the proxies quite a bit (by eliminating reflection).

That said, for CGLIB 2.0 we are adding some new code which will both increase the performance of the proxies even further while also seriously reducing the number of generated classes.

Chris