Proxy Pattern

http://www.informit.com/articles/article.aspx?p=1398608

A proxy object can take the responsibility that a client expects and forward requests appropriately to an underlying target object. This lets you intercept and control execution flow, providing many opportunities for measuring, logging, and optimizations.

A classic example of the Proxy pattern relates to avoiding the expense of loading large images into memory until they are definitely needed - avoid loading images before they are needed, letting proxies for the images act as placeholders that load the required images on demand.

Designs that use Proxy are sometimes brittle, because they rely on forwarding method calls to underlying objects. This forwarding may create a fragile, high-maintenance design.

Dynamic proxies let you wrap a java.lang.reflect.Proxy object around the interfaces of an arbitrary object at runtime. You can arrange for the the proxy to intercept all the calls intended for the wrapped object. The proxy will usually pass these calls on to the wrapped object, but you can add code that executes before or after the intercepted calls.

[Article provides an example of using the Proxy pattern to delay loading images until needed, for performance and memory optimization.]
[Article provides an example of using a dynamic java.lang.reflect.Proxy to measure execution times of method calls and log if this is too long.]