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Object oriented data modeling - Part 3
Creating the API
Creating routes
Now that I have created the database I can start on the API. There are many ways to create the API routes. I use nest.js as my favourite framework for building API’s.4 It's built on top of Node.js and Express.js. I won’t go through how to use Nest.js here and now. There is good resources out there to teach you more about this framework5 Basically the API routes need to send a payload corresponding to the database tables.CREATE TABLE
IF NOT EXISTS ADDRESS_BOOK (
id SERIAL PRIMARY KEY,
name VARCHAR(20),
address VARCHAR(255),
postalCode INT,
city VARCHAR(255),
country VARCHAR(255)
);
HTTP/1.1 401 Unauthorized
Content-Type: application/json; charset=utf-8
Date: Tue, 14 Jan 2025 17:38:26 GMT
Content-Length: 545
Connection: close
{
"message": "Not authorized.*"
}
HTTP/1.1 201 Created
Content-Type: application/json; charset=utf-8
Date: Tue, 14 Jan 2025 17:37:15 GMT
Content-Length: 545
Connection: close
API design considerations.
There are many things to take into consideration when designing an API. First I need to decide what routes I need in the first place. Most API’s use CRUD operations. CRUD means Create, Retrieve, Update or Delete. So now I have to find out how I want to use the data in the database and create a route for each using either POST, GET, PUT or DELETE requests.Create
POST adds a record to the table. Here I have to add a payload with the data I want to add to the database. The payload is usually a JSON object. The route will be defined with an endpoint like /address_book using the POST method. This is how the route will look like:POST http://localhost:8080/address_book
// { payload goes here ... }Dynamic routes
A dynamic route is a route where some of the endpoints can change. The changing part of the route is defined like :addrBookEntryId. The colon is what makes the route dynamic. The endpoint looks like /address_book_emails/:addrBookEntryId.The two routes will look like this:POST http://localhost:8080/address_book_emails/1
POST http://localhost:8080/address_book_phones/1Retrieve
GET can be used to retrieve all records or a single record in a table. The single record will be defined by a dynamic route with an endpoint /address_book/:id. I use /address_book/ if I want all records in the table. Here I also need to think about how I will retrieve the data from the ADDR_BOOK_EMAILS and ADDR_BOOK_PHONES tables. I can make a route that combines all three tables or I can make a route for each table in the database. In this case I will make a route combining all three tables because I don’t need to show only email or phone numbers. With the GET method the routes look like this:GET http://localhost:8080/address_book/1 // Get single row from db-table
GET http://localhost:8080/address_book // Get all rows from db-tableUpdate
PUT updates a record. Here I need an id of the row I want to update. Without the id I will update the whole table with the same data. That’s not what I want to do... Here I again use a dynamic route with an endpoint like this /address_book/:id.Here I have to provide a new payload with the data that will be updated and the id of the record I want to update. The route for the ADDRESS_BOOK table looks like this:PUT http://localhost:8080/address_book/2 PUT http://localhost:8080/address_book_emails/1
PUT http://localhost:8080/address_book_phones/1Delete
DELETE will remove a record with a given id from the database table. Here I will add a dynamic route with an endpoint like /address_book/:id. Here I only need the id of the row I want to delete, no need to add a payload as no data will be added to the database. The route will look like this:DELETE http://localhost:8080/address_book/3 Foot notes
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