38. What is Hibernate proxy


The proxy attribute enables lazy initialization of persistent instances of the class. Hibernate will initially return CGLIB proxies which implement the named interface. The actual persistent object will be loaded when a method of the proxy is invoked.

Anyone using Hibernate for any length of time has no doubt run into the dreaded " problem" when using polymorphic collections. In proxyHibernate, lazy loading of persistent relationships and collections is facilitated by proxies. For example, let's say you have a LooneyBin object that has a collection of Nutter objects that is lazily loaded. If you call looneyBin.getNutters(), Hibernate will only load the ID and version number of the Nutter objects, thus saving all the work of loading individual objects until later. You think you have all the related Nutter objects, but what you really have is a collection of proxies. The thinking is that if you have a collection of a few hundred items, chances are good that you'll only work with a few of them, so why go through the effort of instantiating all the objects. This can be a huge performance gain in certain situations.


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