What's up geeks and welcome to the channel! When the term proxy comes up, the first thing everyone thinks of are proxy servers and gateways. In networking, a proxy is an intermediary server that separates end users from the destinations or websites that they browse. You see if you're using a proxy server the traffic flows through that server on its way to the address you requested, the request then comes back through that same proxy which forwards the data received from the website to you.
Now, if that's all of its job, why bother having a proxy server? Why not just go straight to the website and back? Well, proxy servers do much more than forward web requests. These servers act as a firewall and web filters, provide shared network connections, and may cache specific data to speed up common requests. A good proxy server keeps users and the internal network protected from bad stuff you can find on the internet, providing and ensuring a high level of privacy and security.
Okay, all of that is great but what does it have to do with today's topic? Suppose the Internet is a class in your application, and every time a user tries to connect to a particular website he or she can create an instance of that class, call the connectTo method, and boom, it's done! For the sake of the example we will be printing out some text, but feel free to do whatever you want within this method. Now, a new requirement for this internet class is to restrict access to a couple banned websites for particular users, however if we restrict access to these websites within the internet class, no one will be able to access them all over the internet ever! So what we need is kind of an intermediary server, a proxy, that checks the user requests among a list of banned websites, and if the user tries to access any of these websites an access denied error will pop up for example.
Let's take another example, speed of access and caching. Suppose you have a VideoDownloader class, this class takes the name of the video you want to download, then connects to YouTube, downloads the video, retrieves all its metadata and the download location corresponding to that video and returns with all this info to you using the video object you see. Now, notice how every time we need a particular video, that video gets downloaded all over again, even if it was previously downloaded. To avoid this what we need is some caching mechanism that stores the information related to videos we already downloaded, sparing us the need to do it again. The proxy class you see here will provide exactly this functionality. The proxy will implement the same interface as the original downloader and will delegate to the original service all the work, however it will keep track of the downloaded files using a HashMap and will return the cached result to the user if they request the same video multiple times.
So, if we go back to the same client call we had, you can clearly see that the two videos requested are now being downloaded once each instead of five times as we previously saw. Okay, let's go ahead now and take a look at the structure or class diagram of the proxy pattern while trying to relate it to the internet and caching examples we just implemented. First, the Service interface which was represented by both the Internet and VideoDownloader interfaces in our previous examples. This interface is that of the service, and the proxy must follow this interface to be able to disguise itself as a service object. The service on the other hand represents the actual implementation of that interface, it is a class that provides some useful business logic for our application, it was represented by both the RealInternet and RealVideoDownloader classes in our examples. The next thing you may have noticed is the Proxy class, which of course was the ProxyInternet and ProxyVideoDownloader classes. This class has a referenced field that points to a service object, after the proxy finishes the work it was intended to do, usually it passes the request to the service object. And finally the last piece of our diagram; the Client. The client should work with both services and proxies via the same interface, by doing that the client can pass a proxy object to a code that expects a service object.
So to sum everything up, the proxy design pattern allows you to control the access to a particular object by performing something before or after the request reaches that object. To do that the proxy implements the same interface of the original object in question allowing it to be used as a substitute for that object. Additionally, the proxy can manage the lifecycle of the service object if clients don't care about it, and the proxy object will still work even if the service object isn't ready or is not available. Finally by applying this pattern you will be applying the open-closed principle as you can introduce new proxies without changing the service nor the clients. So that's it for this video, I hope it was helpful. Thank you guys for watching, take care, and I will see you in the next one!
Q: What is a proxy server?
A: A proxy server is an intermediary server that separates end users from the destinations or websites they browse by forwarding web requests and providing additional security and privacy features.
Q: What are the benefits of using proxy servers?
A: Proxy servers act as firewalls, web filters, provide shared network connections, and may cache data to speed up common requests. They offer increased privacy, security, and protection for users and internal networks.
Q: How is the proxy pattern used in programming?
A: In programming, the proxy pattern is used to create an intermediary server that performs actions before or after a request reaches the actual object. It allows for access control, caching, and managing the lifecycle of the original object.
Q: Can you provide an example of implementing the proxy pattern for caching in programming?
A: In programming, a proxy class is created to store cached information related to objects. This proxy class implements the same interface as the original object and delegates work to the original service while keeping track of downloaded files using caching mechanisms.
Q: What is the structure of the proxy pattern and how is it related to internet and caching examples?
A: The proxy pattern consists of a service interface, a service implementation, a proxy class, and a client. The proxy disguises itself as the service object and can control access, manage lifecycle, and improve performance through caching, as demonstrated in internet and caching examples.
Q: What are the benefits and applications of the proxy design pattern?
A: The proxy design pattern allows for access control, managing object lifecycle, and implementing additional functionality before or after requests reach the actual object. It follows the open-closed principle and enables the introduction of new proxies without changing existing services or clients.
