Routing & Requests

The request type makes the difference!

A typical project setup will have of a frontend application that requests something and a backend that retrieves this data from the database and returns it to the frontend application.

Many Single Page Applications (SPA) and Progressive Web Apps (PWA) nowadays are programmed in JavaScript and use the JSON format to communicate between the frontend and backend. Typically, the frontend app will want to do a number of things:

  • Get data for an existing entry from the backend

  • Create or insert a new entry, e.g. add a new item to the to-do or shopping list

  • Update an existing entry

  • and finally delete an item from the database

The idea behind a RESTful Api is to define endpoints (URLs) that the frontend application can communicate with to get the job done. But instead of defining separate URLs for every operation needed (/api/get/entry, /api/save/entry, /api/delete/entry) or passing an action as request parameter (?action=save) it uses HTTP Request types to make clear, if an entry should be retrieved, inserted, updated or deleted.

Same URL - different actions!

Most of the time you even have the same URL for every operation - but depending on the type of request and the request-body passed, different operations are executed:

Method

URL

Request body / payload

typical operation

GET

/api/example/1

(none)

Get entry with uid [1] from database

PUT

/api/example/1

{"title":"Update!", "text":"nice"}

Update full entry with uid [1] in database

PATCH

/api/example/1

{"text":"fine"}

Update parts of entry with uid [1] in database

DELETE

/api/example/1

(none)

Delete entry with uid [1] in database

POST

/api/example

{"title":"New!", "text":"someone"}

Insert a new entry in database

Hint

In many cases, the backend will not make a difference between a PUT and PATCH request. Both are intended to update existing data. But if you are interested in the details, you can find a good explanation on this page.

Route a request to endpoints

The whole deal is about getting a certain HTTP Request Type "connected" to a Controller and method of your Api that will then take care of the rest: Retrieving, updating, inserting or deleting data.

There are two basic ways to accomplish this task: