Imagine a team of developers working on a mobile app for iOS and Android and requires a RESTful Web Service to perform CRUD operations with toys. We definitely don't want to use a mock web service and we don't want to spend time choosing and configuring an ORM (short for Object-Relational Mapping). We want to quickly build a RESTful Web Service and have it ready as soon as possible to start interacting with it in the mobile app.

We really want the toys to persist in a database but we don't need it to be production-ready. Therefore, we can use the simplest possible relational database, as long as we don't have to spend time performing complex installations or configurations.

Django REST framework, also known as DRF, will allow us to easily accomplish this task and start making HTTP requests to the first version of our RESTful Web Service. In this case, we will work with a very simple SQLite database, the default database for a new Django REST framework project.

First, we must specify the requirements for our main resource: a toy. We need the following attributes or fields for a toy entity:

• An integer identifier
• A name
• An optional description
• A toy category description, such as action figures, dolls, or playsets
• A release date
• A bool value indicating whether the toy has been on the online store's homepage at least once

In addition, we want to have a timestamp with the date and time of the toy's addition to the database table, which will be generated to persist toys.

In a RESTful Web Service, each resource has its own unique URL. In our web service, each toy will have its own unique URL.

The following table shows the HTTP verbs, the scope, and the semantics of the methods that our first version of the web service must support. Each method is composed of an HTTP verb and a scope. All the methods have a well-defined meaning for toys and collections:

In the previous table, the GET HTTP verb appears twice but with two different scopes: toys and collection of toys. The first row shows a GET HTTP verb applied to a toy, that is, to a single resource. The second row shows a GET HTTP verb applied to a collection of toys, that is, to a collection of resources.

We want our web service to be able to differentiate collections from a single resource of the collection in the URLs. When we refer to a collection, we will use a slash (/) as the last character for the URL, as in http://localhost:8000/toys/. When we refer to a single resource of the collection we won't use a slash (/) as the last character for the URL, as in http://localhost:8000/toys/5.

Let's consider that http://localhost:8000/toys/ is the URL for the collection of toys. If we add a number to the previous URL, we identify a specific toy with an ID or primary key equal to the specified numeric value. For example, http://localhost:8000/toys/42 identifies the toy with an ID equal to 42.

We have to compose and send an HTTP request with the POST HTTP verb and http://localhost:8000/toys/ request URL to create a new toy and add it to the toys collection. In this example, our RESTful Web Service will work with JSON (short for JavaScript Object Notation), and therefore we have to provide the JSON key-value pairs with the field names and the values to create the new toy. As a result of the request, the server will validate the provided values for the fields, make sure that it is a valid toy, and persist it in the database. The server will insert a new row with the new toy in the appropriate table and it will return a 201 Created status code and a JSON body with the recently added toy serialized to JSON, including the assigned ID that was automatically generated by the database and assigned to the toy object:

POST http://localhost:8000/toys/ 

We have to compose and send an HTTP request with the GET HTTP verb and http://localhost:8000/toys/{id} request URL to retrieve the toy whose ID matches the specified numeric value in {id}. For example, if we use the request URL http://localhost:8000/toys/25, the server will retrieve the toy whose ID matches 25. As a result of the request, the server will retrieve a toy with the specified ID from the database and create the appropriate toy object in Python. If a toy is found, the server will serialize the toy object into JSON, return a 200 OK status code, and return a JSON body with the serialized toy object. If no toy matches the specified ID, the server will return only a 404 Not Found status:

GET http://localhost:8000/toys/{id} 

We have to compose and send an HTTP request with the PUT HTTP verb and request URL http://localhost:8000/toys/{id} to retrieve the toy whose ID matches the value in {id} and replace it with a toy created with the provided data. In addition, we have to provide the JSON key-value pairs with the field names and the values to create the new toy that will replace the existing one. As a result of the request, the server will validate the provided values for the fields, make sure that it is a valid toy, and replace the one that matches the specified ID with the new one in the database. The ID for the toy will be the same after the update operation. The server will update the existing row in the appropriate table and it will return a 200 OK status code and a JSON body with the recently updated toy serialized to JSON. If we don't provide all the necessary data for the new toy, the server will return a 400 Bad Request status code. If the server doesn't find a toy with the specified ID, the server will only return a 404 Not Found status:

PUT http://localhost:8000/toys/{id}

We have to compose and send an HTTP request with the DELETE HTTP verb and request URL http://localhost:8000/toys/{id} to remove the toy whose ID matches the specified numeric value in {id}. For example, if we use the request URL http://localhost:8000/toys/34, the server will delete the toy whose ID matches 34. As a result of the request, the server will retrieve a toy with the specified ID from the database and create the appropriate toy object in Python. If a toy is found, the server will request the ORM delete the toy row associated with this toy object and the server will return a 204 No Content status code. If no toy matches the specified ID, the server will return only a 404 Not Found status:

DELETE http://localhost:8000/toys/{id}