RESTful and HTTP APIs in Pyramid Transcripts
Chapter: What is REST?
Lecture: HTTP verbs

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0:01 When building http services, it's really important
0:03 to make proper use of the http verbs.
0:06 Now, there are many esoteric verbs, but the four that appear all the time
0:11 in restful or http services are get, post, put and delete.
0:16 So let's talk about those quickly and then we'll see an example.
0:19 So get is the one that happens by default, if you go and type a url into your browser
0:24 and you hit enter, that's a get request, right, just send me the resource there.
0:29 And the idea is that this should be basically read only,
0:32 it should have no other effect other than retrieving the data.
0:35 You don't want to initialize the service this way,
0:38 you don't want to require that you do a get request to something
0:41 before you can do something else, this is just a read this property type of thing.
0:46 And notice that I have it marked as item potent, and what that means is
0:49 if I call it once, if I do a get request to some url certain parameters,
0:55 then I call it again and again and again, it should have no effect,
0:59 the second, third and fourth time.
1:01 So if I apply this operation more than once, it shouldn't change it, that's item potent.
1:06 And item potent is super important for services
1:09 because the item potent verbs are casual,
1:12 if you do a request and it goes to some kind of proxy server
1:15 or even cashing in your browser, it can see that you did the get request to this
1:19 and maybe we don't need to run this operation again,
1:23 we can just return the cash local copy,
1:26 because we know it's item potent we know it should have no effect.
1:29 Now, the other popular one that you see all the time in web pages and stuff is post.
1:35 If you submit a form that typically submits something as a post
1:39 and the idea with these post operations is that there is
1:42 some kind of body submitted to the server
1:45 maybe this is form and coded data, key value, key value, key value
1:48 like you might have an html form, it is also a very common for that to be json,
1:51 but however it's represented, you basically go into the server
1:54 and saying I would like you to accept this new piece of data,
1:58 maybe this new book, I'm trying to create a book in the service
2:01 or a new user or something like that, and then the service is supposed to respond
2:06 and say I have created it and you can find it over here,
2:10 this is the one operation of the popular ones that's not item potent.
2:14 If I say create a new book and I give it some information
2:17 and I ask you to create a book again,
2:20 chances are you now have two books with the same title or something like that,
2:23 unless you have good validation, so this one is not item potent and that's important.
2:27 And the idea here is, you're going to submit this book,
2:30 but you don't really know like what the url
2:32 or the primary key or whatever it's going to be,
2:35 just hey here's a new book create it and tell me where it goes.
2:38 Similar to this, but if you know where it's going to go,
2:40 like if you're creating a cms say, and like I want to create a new page in this site
2:45 and the url is going to be the this, well possibly we would do a put instead of a post
2:50 and we put it to that address to say create this page here
2:54 and so it's much like a post, you submit a body
2:57 and the server except it and creates a thing,
3:00 but you're telling the server you're letting the client decide what is the id basically.
3:03 And finally, if it makes sense for an item to be deleted
3:07 so in our book store we want to delete the book
3:10 or maybe delete a comment or something like that,
3:13 we could do an http delete operation against some resource
3:16 and just like if we put the same data to the same url over and over,
3:20 it's still the same data, the same url, deleting the thing
3:23 one or a hundred times, it's still gone.
3:25 So these other two put and delete operations are also item potent.