How to resolve Postman unable to send request body to express application error ?

Encountering difficulties when attempting to send a request body from Postman to your Express application can be a frustrating experience. This issue may manifest in various ways, such as empty request bodies or unexpected behavior on the server side. In this troubleshooting guide, we will explore different approaches to resolve this problem and ensure seamless communication between Postman and your Express application.

Following are the different approaches we will use to resolve the error:

Check Content-Type Header:

When troubleshooting issues with sending request bodies from Postman to your Express application, it’s crucial to inspect the Content-Type header in your Postman request. This header informs the server about the type of data being sent in the request body. Ensure that the Content-Type header matches the expected format in your Express application.

For example, if your server expects JSON data, set the Content-Type header in Postman to application/json. If you are sending form data, use application/x-www-form-urlencoded. Mismatched or missing Content-Type headers can lead to the server misinterpreting the request body, resulting in failed communication.

Use Body Parsing Middleware:

To successfully handle incoming request bodies in your Express application, you need to employ body parsing middleware. The middleware is responsible for parsing the raw request body into a usable format for your server to process. In this example, we’ll use the popular body-parser middleware.

You can use body-parser by installing it with:

npm install body-parser

Then, include it in your Express app:

const bodyParser = require('body-parser');
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));

These lines of code tell Express to use body-parser for JSON and URL-encoded form data. Without this middleware, your Express application might not be able to properly parse and access the request body.

Check for Middleware Order:

The order in which middleware is applied in your Express application matters. If body parsing middleware is placed after your route handlers, the request body might not be processed before reaching your route logic.

Ensure that the middleware for parsing the request body is added before your route definitions. Here’s an example:

const express = require('express');
const bodyParser = require('body-parser');
const app = express();
// Body parsing middleware should come before route handlers
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));
// Routes
app.post('/api/postData', (req, res) => {
  const data = req.body;
  res.json({ receivedData: data });
});

By organizing your middleware in the correct order, you allow the body parsing middleware to process the request body before it reaches your route, ensuring that the data is correctly parsed and accessible within your route handler.

Steps to setup the Express App:

Step 1: Initializing the Node App using the below command:

npm init -y

Step 2: Installing the required packages:

npm install express

Project structure:

The updated dependencies in package.json file for backend will look like:

"dependencies": {
    "express": "^4.18.2",
}

Example: In this example, we will create a simple express application to send data using POSTMAN using Body Parsing Middleware.

• Express Setup: The code sets up an Express.js server to handle HTTP requests.
• Middleware Configuration: It uses the body-parser middleware to parse incoming request bodies as JSON (app.use(bodyParser.json())) and to handle URL-encoded data (app.use(bodyParser.urlencoded({ extended: true }))). Additionally, it serves static files from the ‘public’ directory (app.use(express.static(‘public’))).
• HTTP Routes: The server defines two routes: POST /api/postData: Accepts JSON data in the request body, stores it in the receivedData variable, and responds with a JSON containing the received data, GET /: Responds with a JSON containing the data stored in the receivedData variable.
• Server Start: The server listens on port 3000, and a log message is printed to the console once the server is running.

Javascript

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

const app = express();
const port = 3000;

// Middleware
app.use(bodyParser.json());
app.use(
    bodyParser.urlencoded(
        {
            extended: true
        }));
app.use(express.static('public'));

// Variable to store received data
let receivedData = null;

app.post('/api/postData',
    (req, res) => {
        const data = req.body;
        receivedData = data;
        res.json(
            {
                receivedData: data
            });
    });

app.get('/',
    (req, res) => {
        res.json({ receivedData });
    });

// Start the server
app.listen(port,
    () => {
        console.log(
            `Server is running on http://localhost:${port}`
        );
    });

Test Your express Application using postman:

• Open Postman.
• Create a new POST request.
• Set the request URL to http://localhost:3000/api/postData.
• Go to the Headers section and ensure that the Content-Type is set to application/json.
• In the Body tab, add a JSON payload, for example:

{
  "name": "Dhruvi Trivedi",
  "age": 20
}

Output: