Proxy Pattern

Summary

• The Proxy pattern supports objects that control the creation of and access to other objects.
• The proxy is often a small (public) object that stands in for a more complex (private) object.
• Proxies are interfaces to classes that have sensitive data or slow operations.

Different Types of Proxies

Virtual proxies

• Hands the creation of an object over to another object.
• Useful if the creation process might be slow or might prove unnecessary.

Authentication proxies

• Checks that the access permissions for a request are correct.

Remote proxies

• Encodes requests and sends them across a network.

Smart proxies

• Adds to or changes requests before sending them on.

Class diagram: (see Proxy Pattern code review)

Usage

Use the Proxy pattern when you have objects that:

• Are expensive to create.
• Need access control.
• Access remote sites.
• Need to perform some action whenever they are accessed.