API Interaction

Have you ever wanted to be able to interact with an API endpoint from some web application whether it is yours or somebody elses?

Its rhetorical. I don’t care whether you have or not. You’re gonna learn today.

Playing with web applications you likely remember atleast 2 operations of interfacing with a web application.

Those being:

GET and POST methods. Well there are 2 more that are important called PUT and DELETE.

As a quick refresher we will go through what the first two mean and add the last two to catch everyone up to speed.

GET - This is when you are reading the information from the web application and requesting the page.

POST - This is when you are sending data to the web application.

• example being when you login on some page or are adding something to a database.

PUT - This operation is utilized when making a change on the server such as an update to your username.

DELETE - This obviously means delete but much like when you’re using the GET request you can point the DELETE operation at the path you wish to delete and like magic it’s gone.

There are two bonus operators that can be used in a web application as well but they are not frequently used. Those are: OPTIONS and PATCH.

OPTIONS - Gives the user the possible options available to him when communicating with the web application

PATCH - Works just like PUT the only difference being that it is used to change some part of an entry not the entire thing.

• example being when you want to change your first name to a nick name but leave your last name the same you can use PATCH

Now that we have talked about it I’ll give some snippets of a command line to show you how to write them.

We will be using cURL as a resource to retrieve and change information. Get used to it.

Curl by default uses the GET request so I will not be showing a screenshot of the first operation but will give you the example in text.

curl https://google.com

When you are dealing with an API of some kind it will still return the information to you much like any other time you have used it except it may look jumbled or in another format such as json.

Json text

If we want to take the json text and make it look exceptionally better and in the correct format we can add a pipe and the command “jq” to the command line.

formatted json

Awesome. So we understand the GET operation with an API. Lets check out the POST.

When posting we want to use the switch “-X” POST followed by the URL and some data. To post the data we need the “-d” switch. Lastly, we need to change the end of the content type to json since we already know that is what we will be receiving back for information.

POST: Creating a new entry

We created a new entry. Now you can do a GET to request the information and see your entry provided in the json format.

It worked.

Lets see PUT in action. Remember, this changes entries. Let’s grab another entry and show the change.

PUT much like POST requires “-X”, “-d” and “-H” and the data that is being changed. The differences is that you need to change POST to PUT and specify in the URL which entry you wish to change. Just like before we will check to see if it worked by a GET request to the API page.

PUT request

Detroit now changed to Dallas

Then finally the simplest one to understand. Deleting entries from a database on an endpoint.

DELETE on London

When you do a GET request on the deleted information you are presented the result of an empty array. That empty array is proof of a deleted entry.

I hope you learned something, and if you didn’t I hope it was a decent refresher and you enjoyed my presentation on the subject. If not, no worries I’ll keep pushing out content and there’s bound to be something you enjoy.

As always, stay curious my friends.