Proxies should observe the following contract:

• They should implement all interfaces that the configuration indicates should be proxied.
• They should implement the Advised interface.
• They should implement the equals method to compare proxied interfaces, advice, and target.
• They should be serializable if all advisors and target are serializable.
• They should be thread-safe if advisors and target are thread-safe.

Proxies may or may not allow advice changes to be made. If they do not permit advice changes (for example, because the configuration was frozen) a proxy should throw an AopConfigException on an attempted advice change.