Proxy

• Also known as: Surrogate
• An object representing another object
• Provide a surrogate or placeholder for another object to control access to it

Proxy

• Maintains a reference that lets the proxy access the real subject. Proxy may refer to a Subject if the RealSubject and Subject interfaces are the same.
• Provides an interface identical to Subject's so that a proxy can be substituted for for the real subject.
• Controls access to the real subject and may be responsible for creating and deleting it.
• Other responsibilites depend on the kind of proxy:

• Remote proxies are responsible for encoding a request and its arguments and for sending the encoded request to the real subject in a different address space.
• Virtual proxies may cache additional information about the real subject so that they can postpone accessing it. For example, the ImageProxy from the Motivation caches the real images's extent.
• Protection proxies check that the caller has the access permissions required to perform a request.

Subject

• Defines the common interface for RealSubject and Proxy so that a Proxy can be used anywhere a RealSubject is expected.

RealSubject

• Defines the real object that the proxy represents.