Week 9, Day 1 Proxy SE-2811 Slide design: Dr. Mark L. Hornick Content: Dr. Hornick Errors: Dr. Yoder 1

Simon Concluded Implementing Simon Model Maintaining scores Simon’s count Player’s count View Playing sounds Loading sounds Controller Initiating sounds Playing the sequence SE-2811 Dr.Yoder 2

The Proxy Pattern has many variations, but in general: The Proxy Pattern uses an proxy object as a surrogate (aka stand-in or placeholder) that acts like another object When might you do this? SE-2811 Dr. Mark L. Hornick 3

SE-2811 Dr. Josiah Yoder 4

Generic Proxy Pattern: A Client programs to a Subject, which may be a RealSubject or a Proxy SE-2811 Dr. Mark L. Hornick 5

The Stub Proxy is a (temporary) placeholder for the Real Subject Sometimes the Real Subject is not available For example: still under development The Stub Proxy can provide implementation of the Subject interface to varying degrees: 1. Just enough to compile without error 2. To allow rudimentary Subject functionality 3. To provide a complete emulation of the RealSubject 6

Stub Proxy – the Real Subject emulator SE-2811 Dr. Mark L. Hornick 7

The Protection Proxy controls access to a resource (the Real Subject) that is restricted by access rights The Protection Proxy provides predefined access to certain functionality implemented by the Real Subject, but Purposely limited by the access rights built into the Protection Proxy For example, the ability to query (but not modify) a protected database 8

The Protection Proxy limits access to the Real Subject SE-2811 Dr. Mark L. Hornick 9 ProtectionProxy

The Virtual Proxy controls access to a resource (the Real Subject) that is expensive to create or use The Virtual Proxy provides access to all of the functionality implemented by the Real Subject, but More quicky/cheaply Acts as a surrogate until the Real Subject becomes available 10

The Virtual Proxy provides all functionality of the Real Subject SE-2811 Dr. Mark L. Hornick 11 The Virtual Proxy controls access to the Real Subject, and is often responsible for creation of the Real Subject

The Remote Proxy provides local access to a remote resource (the Real Subject) The Remote Proxy handles the details of accessing a remote resource Remote Access can be implemented in many different ways, using different communication protocols Simple sockets Remote Method Invocation HTTP-based (e.g. web-services) … 12

The Remote Proxy allows the Client to think it is accessing a local resource SE-2811 Dr. Mark L. Hornick 13

SE-2811 Dr. Mark L. Hornick 14