Applied Design Patterns with Java

Structural :: Proxy (207) {C ch 15}

Example - UML : Display

Example - Java :: Patterns\Structural\Proxy

Pattern Concept: to represent with a simpler, lightweight object an object that is complex or time-consuming to create. The simpler object is a temporary subsitute for the actual object.

Issues and Consequences of the Proxy pattern include:

• A Proxy is useful for objects with large memory footprints and significant load or transfer times, remote objects on a network that are unavailable or slow to open, and for objects with controlled access (the Proxy validates the access rights to the actual object);
• A Proxy is useful for objects employed in a 'Copy-on-Write' scenario. Only when the object is changed is the actual object updated;
• Both the Adapter and Proxy provide a thin layer around an object, but the Adapter exposes another interface but the Proxy provides the same interface;
• A Decorator provides the same interface to its contained object and adds new functionality to an object, but the Proxy does not add any new methods, it simply controls access to the contained object.

The example Java program is named 'ProxyDisplay'. The UML diagram is above, and the list of Java files is below:

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