tl;dr The Proxy pattern ...
Some questions arise out of this:
A Proxy tends to lead to several consequences:
If the Proxy wraps another object entirely (such as the Java examples in the Variations section below), it might be seen as acting more like a Decorator than a Proxy, depending on whether the behavior of the underlying object is being modified.
A couple of different takes on the Proxy include:
This was published in Pattern-Oriented Software Architecture, Vol 1.
Often called "stubs and skeletons" (CORBA) or "proxies and stubs" (DCOM), distributed system RPC toolkits often code-generated Proxy instances at compile-time, which could then be called (client-side) or subclassed to provide implementation (server-side). In this manner, the generated client-side Proxy is acting as a distributed form of Flyweight, often to the point that a given Proxy instance would in fact notify the server of its existence in order to keep the server-side instance alive longer via reference-counts.
Java used the Proxy pattern for authorization and encryption with the creation of two separate object types that would "wrap" a Java Serializable object and add additional layers of functionality;
java.security.SignedObject, which allowed for creating authentic runtime objects whose integrity cannot be compromised without being detected, and
java.security.GuardedObject, which encapsulates a target object and a
Guard object, such that access to the target object is possible only if the guard allows it, and a `javax.crypto.SealedObject, which can encapsulate the original object in serialized format (i.e., a "deep copy") and encrypt its serialized contents using a cryptographic algorithm.
Last updated: 25 February 2022Tags: pattern structural