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How Do We Get Data from the Web?4:54 with Ken Alger
How does the web work? What happens when we click on a link? How can we get weather data from a website into an Android app?
[MUSIC] 0:00 [SOUND] Since you're watching this video, you're obviously an internet pro. 0:02 Have you ever wondered how it actually works though? 0:08 What's the deal with the HTTP portion in URLs? 0:12 What actually happens when you click on a link? 0:16 [SOUND] HTTP stands for HyperText Transfer Protocol. 0:18 Simply put, 0:22 this is the protocol that allows us to communicate over the Internet. 0:23 We'll see a concrete example shortly, but I think it's useful to have 0:28 a basic understanding of how sending and receiving data over the web works. 0:32 That being said, this isn't a deep dive into HTTP. 0:37 It can be confusing and overwhelming for me too. 0:42 So don't worry if you also feel under the clouds with these concepts. 0:45 The Request/Response Model of computing powers the web. 0:49 What this means is that we make a request to a certain place, in a certain format. 0:53 The place is accessed by an identifier, which we usually refer to as a URI, 0:58 or uniform resource identifier, most commonly with webpages. 1:05 The URI is the web address or URL. 1:10 Notice the word address in web address, that's not an accident. 1:14 The URL is like the address for a building. 1:19 It's where you'll find the resource. 1:22 I've included some information in the teacher's notes, 1:24 if you'd like to read more about URIs and URLs. 1:26 We send a request to a specific location. 1:30 The request is the first half of the process. 1:33 The second half is the response from that location, or URI. 1:35 This was the process we talked about previously, 1:41 when we discussed the Dark Sky API. 1:44 This is a rather simplified discussion, which for our purposes is fine, 1:47 as the details of how a network sends bites and bits back and 1:51 forth are obstructed away from us. 1:55 Modern programming involves adding layers of abstraction. 1:58 Each layer of abstraction makes it easier for 2:02 us to concentrate on the higher level tasks we are concerned with. 2:05 Prior to these levels of abstraction, 2:09 we would have to worry about how to send the bits ourselves. 2:11 That can be a real headache. 2:14 Why is all this important to us and our Stormy app? 2:16 Well, we are getting ready to request some data from Dark Sky, 2:19 and we do so with an HTTP GET request. 2:23 Programming is truly about working with data that can be boiled down to four basic 2:27 operations, creating data, reading or 2:31 retrieving data once it's been created, updating the data, and deleting it. 2:35 You'll often hear these basic operations referred to by their acronym, CRUD. 2:40 HTTP has its own operations that correspond to this CRUD, as we see here. 2:46 Most web programming primarily deals with two of these operations, POST and GET. 2:52 Since we aren't creating a weather forecast with Stormy, 2:57 we won't worry about the POST method. 3:01 However, we will be using GET requests to retrieve or read data from a server. 3:03 Whenever we visit a website, our browser issues an HTTP GET request to, 3:10 well, request the latest version of a webpage, 3:15 video, weather forecast, or whatever it is we are wanting to view. 3:18 I've put additional information in the teacher's notes about HTTP methods for 3:23 further reading. 3:27 Android clients are no different. 3:29 We will be making an HTTP GET request to the Dark Sky API servers. 3:32 Using the URI in the developer's documentation we've previously looked at, 3:37 we send a request with the exact information we want. 3:42 The servers then send a response that includes the weather data. 3:45 It's up to us then to handle the data we receive and use it in our application. 3:49 If we use the web browser example, the server sends back a response with HTML, 3:53 and the browser converts it to a webpage we can view. 3:59 Recall that this is the power of the interface portion of the API in action. 4:03 We don't need to know how Dark Sky gets their data, 4:08 as long as we get back a response in an agreed upon format. 4:11 Sounds easy enough, right? 4:16 Well, as you might have guessed, it isn't quite as simple as I've made it out to be. 4:18 Sure, those basic concepts hold true. 4:24 But we're going to have to learn how to create and 4:27 send a web request, receive a response, and handle the response. 4:29 We'll need to think about what happens if we get an error in the response as well. 4:33 Additionally, we need to make sure we are performing these types of requests 4:38 in the background, to ensure our app remains responsive. 4:42 Before we jump into our project again, 4:46 let's discuss networking as it applies to mobile devices in the next video. 4:49
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