Proxy Pattern

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Design Patterns - Proxy Pattern

There are many different flavours of Proxy, depending on it's purpose. You may have a protection proxy, to control access rights to an object. A virtual proxy handles the case where an object might be expensive to create, and a remote proxy controls access to a remote object.

This pattern is recommended when either of the following scenarios occur in your application:

• The object being represented is external to the system.
• Objects need to be created on demand. 
• Access control for the original object is required
• Added functionality is required when an object is accessed.

You'll have noticed that this is very similar to the Adapter pattern. However, the main difference between bot is that the adapter will expose a different interface to allow interoperability. The Proxy exposes the same interface, but gets in the way to save processing time or memory.

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Proxy Pattern Tutorial with Java Examples

If you've read my "Decorate Your Java Code" (JavaWorld, December 2001), you may see similarities between the Decorator and Proxy design patterns. Both patterns use a proxy that forwards method calls to another object, known as the real subject. The difference is that, with the Proxy pattern, the relationship between a proxy and the real subject is typically set at compile time, whereas decorators can be recursively constructed at runtime.

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Java Design Patterns