Proxy is a structural design pattern that lets you provide a substitute or placeholder for another object. A proxy controls access to the original object, allowing you to perform something either before or after the request gets through to the original object.

Proxy is applicable whenever there is a need for a more versatile or sophisticated reference to an object than a simple pointer.Here are several common situations in which the Proxy pattern is applicable:

• Remote proxy provides a local representive for an in a different address space.
• Virtual proxy creates expensive objects on demand.
• Protection proxy controls access to the original object.

• Proxy :
  • maintains a reference that lets the proxy access the real subject. Proxy may refer to a Subject if the RealSubject and Subjectinterfaces are the same.
  • provides an interface identical to Subject's so that a proxy can by substituted for the real subject.
  • controls access to the real subject and may be responsible for creating and deleting it.
• 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.