Hi everyone:

I see the hibernate docs http://www.hibernate.org/hib_docs/reference/en/html/performance.html .
The proxy puzzled me some time. Need I have to use proxy if I want to lazy load? If not , what time should I use proxy? I also don't understand how to use interface to implements proxy. Could someone give me a example or tell me how to use proxy to improving performance?

THks in advance!

The best answer to your question is "try it yourself and look at the generated SQL"...


In short, you can have lazy collections and lazy entities.

A lazy collection is a collection that will be fetched from the database the first time you access it. This means the collection won't be populated at the time you retrieve the owning entity.


A lazy entity is an entity whose properties will be loaded from the database the first time you access it. It makes sense (and is usefull) only when the entity is a member of a collection or the target of a many-to-one relationship. In this case, Hibernate won't load the entity but initialize a proxy for it (at this stage, Hibernate knows the entity exists and the correponsing primary key - that's all the proxy contains besides the entity class).

Example: a Child as a one and only one Parent. Suppose the Parent entity is declared lazy. When you load a child, the parent entity will be loaded only at the time you call child.getParent() (returning a populated instance of the Parent class).

It is enough to add 'lazy=true' in the Parent class mapping to make it lazy. Don't botter now with the interface stuff...