The proxy design pattern is probably the most obvious one that is included in Java EE. Injected bean references contain in almost all cases not a reference to the actual instance, but a proxy. Proxies are thin wrappers around instances that can add certain functionalities. The client doesn't even notice that it interacts with a proxy instead of the actual object.

Proxies enable the cross-cutting functionality which is required in an enterprise environment, such as interceptors, transactions, logging, or monitoring. They are also required to perform dependency injection in the first place.

Application developers typically don't use the proxy pattern directly. However, it is recommended to understand how the proxy pattern works in general and how it's used in the Java EE platform in particular.