Postman

Postman is an incredibly helpful tool for testing and validating our APIs. In this case, REST APIs. Postman is essentially a systematic and user-friendly way to send predefined requests.

Let's open Postman together.

Once you create an account and login, you will be met with a picture of your workspace. Click on Workspaces > My Workspace. There should be nothing there except maybe an example request that we could make. We will now be returning to our previous examples to show how we can make systematic GET requests to the same APIs.

Example API

Additionally, /db/all supports a query param specifying the maximum number of items to return.

I will teach you how to run this program fully, but for the purpose of this exercise,

EXTRA: RESTful Server in Action and Postman

To understand REST API and HTTP methods a step further, let us take a look at a RESTful server in action.

Let's say we are building a TODO app. Take a look at the following code. Pay close attention to what the comments address.

const express = require('express');

const app = express();

var port = process.env.PORT || 8080;

var router = express.Router();

const bodyParser = require('body-parser');

app.use(bodyParser.urlencoded({ extended: false }));
app.use(bodyParser.json());

// The method of the root url. Be friendly and welcome our user :)
router.get('/', function (req, res) {
  res.json({ message: 'Welcome to the TODO app.' });
});

// All HTTP methods under the /todos URL.
router
  .route('/todos')
  // This GET method is in charge of returnning all the todos.
  .get((req, res) => {
    res.json({ message: 'Return all todos.' });
  })
  // This POST methods is used to create a new todo.
  // Its request will have a body, containing the content of the new todo.
  .post((req, res) => {
    res.json({
      message: 'Create a new todo: ' + '1' + ' - ' + req.body.content,
      todo_id: '1',
      content: req.body.content,
    });
  });

// All HTTP methods under the /todos/:todo_id URL.
// The /:todo_id is a parameter within the URL that specifies a particular todo.
router
  .route('/todos/:todo_id')
  // This GET method is used to get the content from a specific todo.
  .get((req, res) => {
    res.json({ message: 'Get the content from a todo.' });
  })
  // We use PUT method to update a todo's content.
  .put((req, res) => {
    res.json({
      message:
        'Update the todo: ' + req.params.todo_id + ' - ' + req.body.content,
      todo_id: req.params.todo_id,
      content: req.body.content,
    });
  })
  // DELETE method is used to delete a todo.
  .delete((req, res) => {
    res.json({ message: 'Delete a todo.' });
  });

app.use('/api', router); // API Root url at: http://localhost:8080/api

app.listen(port);
console.log('Server listenning on port ' + port);

Now with the dummy server ready, how should we send all the HTTP requests? Introduce a new tool in our workflow —— postman.

Let's start the server with npm run start and see how can we interact with the server.

Postman

Postman is a platform for API development. It can easily build and send out API requests.

Once you download and install postman, click new collection on the left side bar to create a new collection of API requests. Let's call it RESTful server test requests.

Then, click on the more button and add a request. Let's first test out the API for the root URL:

// The method of the root url. Be friendly and welcome our user :)
router.get('/', function (req, res) {
  res.json({ message: 'Welcome to the TODO app.' });
});

Create a request and make sure its HTTP method is GET. Our root API url is at http://localhost:8080/api. After you click send, you should be seeing a JSON response body, which consists of a message with the content of "Welcome to the TODO app."

Create API requests using POSTMAN

Postman is a very powerful tool as it can save your API request and resend it again and again at your will. Let's save this and create mroe API requests to test the GET request that fetch all todos and POST that create a new todo.

// All HTTP methods under the /todos URL.
router
  .route('/todos')
  // This GET method is in charge of returnning all the todos.
  .get((req, res) => {
    res.json({ message: 'Return all todos.' });
  })
  // This POST methods is used to create a new todo.
  // Its request will have a body, containing the content of the new todo.
  .post((req, res) => {
    res.json({
      message: 'Create a new todo: ' + '1' + ' - ' + req.body.content,
      todo_id: '1',
      content: req.body.content,
    });
  });

Let's first create a new request, and use http://localhost:8080/api/todos as the request URL. We start by testing out the GET request, and after clicking send, you should see the following JSON as a response:

{
    "message": "Return all todos."
}

Now let's try out the POST request, unlike the GET request, the POST request contains a request body. If the post request does not contain any body, you would receive something like this:

This undefined in the message means that the server does not receive the content of the todo, which should be included in the request body.

To add a request body, click on Body and then select raw. Change the format from TEXT to JSON, and you are ready to write your first request body.

Let's say I want to create a todo with content "hello world todo". Then, we create a JSON like this:

You should be receiving the message with the content you just created in the body.

Resources

Build a RESTful API Using Node and Express 4

What is REST

Postman​

Create API requests using POSTMAN​

Postman

Create API requests using POSTMAN