Gof Creational - Proxy Pattern

• Intent

To provide a surrogate or placeholder for another object to control access to it. The most common impl are remote and virtual proxy.

在這個模式底下，其實主要的做法就是 代理者與被代理者實做同樣的介面，而代理者保有被代理者的實體，每當client端送給代理物件需求時，代理物件就以自身保有的被代理者的實體提供服務。

• Benefits

1. 遠端proxy可以屏蔽實際提供服務的business object 的內容(將實作放在另一個物件裏頭)

2. The virtual proxy can perform optimizations- for example, by creating objects on demand. (?? 跨謀)

• 適用情境 - when a more versatile or sophisticated reference to an object, rather than a simple pointer, is needed.


• 常見的API - javax.ejb.EJBObject (採用proxy pattern)，stub物件在client端提供了proxy物件。


• Class Diagram

[caption id="attachment_209" align="alignnone" width="365" caption="ProxyPattern"][/caption]