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Proxy

proxy

/patterns/proxy/

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Structural

Java

Gang Of Four

Difficulty-Beginner

Also known as

Surrogate

Intent

Provide a surrogate or placeholder for another object to control access to it.

Applicability

Proxy is applicable whenever there is a need for a more versatile or sophisticated reference to an object than a simple pointer. Here are several common situations in which the Proxy pattern is applicable

a remote proxy provides a local representative for an object in a different address space.
a virtual proxy creates expensive objects on demand.
a protection proxy controls access to the original object. Protection proxies are useful when objects should have different access rights.

Typical Use Case

control access to another object
lazy initialization
implement logging
facilitate network connection
to count references to an object

Real world examples

java.lang.reflect.Proxy
Apache Commons Proxy
Mocking frameworks Mockito, Powermock, EasyMock

Credits

Design Patterns: Elements of Reusable Object-Oriented Software