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hediyeh kianmehr
hediyeh kianmehr

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Creating and Calling APIs in Node-RED

Overview

This document explains how to create (make) and call (consume) APIs in Node-RED.

It covers:

  • The basics of what an API is.
  • How to build APIs in Node-RED (CRUD example).
  • How to call APIs from Node-RED (both external and internal).
  • Differences between making and calling APIs.
  • Practical examples with requests & responses.
  • A clear comparison of when to use each approach.

By the end, you’ll understand how Node-RED can act both as an API server and an API client.

Table of Contents

1.What is an API?

An API (Application Programming Interface) allows different applications to communicate with each other.

In web development, APIs are usually HTTP-based, meaning you can use HTTP methods like:

GET → Retrieve data

POST → Add new data

PUT → Update existing data

DELETE → Remove data

2. How to Build an API in Node-RED (Making APIs)

Node-RED makes it easy to build APIs by combining:

HTTP In nodes → Define API endpoints (like /users/getAll)

Function nodes → Process requests (business logic)

HTTP Response nodes → Send results back to the client

Basic flow:

HTTP In → Function → HTTP Response
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Practicing User CRUD API in Node-RED

Method Endpoint Description
GET /users/GetAll Get all users
GET /users/Get/:id Get a single user by ID
POST /users/post Add a new user
PUT /users/put/:id Update a user by ID
DELETE /users/delete/:id Delete a user by ID

3.Example Requests & Responses

3.1 Get All Users

Request:

GET https://codenxa.leanea.com/hediyeh/users/GetAll
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Response:

{
  "users": [
    {
      "id": 1,
      "age": 28,
      "first_name": "Hediyeh",
      "last_name": "Karimi",
      "email": "hediyeh.karimi@example.com",
      "country": "Iran"
    },
    {
      "id": 2,
      "age": 20,
      "first_name": "Ali",
      "last_name": "Rezaei",
      "email": "ali.rezaei@example.com",
      "country": "Iran"
    }
  ]
}
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3.2 Get a User by ID

Request:

GET https://codenxa.leanea.com/hediyeh/users/Get/1
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Response:

{
  "id": 1,
  "age": 28,
  "first_name": "Hediyeh",
  "last_name": "Karimi",
  "email": "hediyeh.karimi@example.com",
  "country": "Iran"
}
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3.3 Add a User

Request:

POST https://codenxa.leanea.com/hediyeh/users/post
Content-Type: application/json
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Body:



{
  "age": 25,
  "first_name": "Sara",
  "last_name": "Ahmadi",
  "email": "sara.ahmadi@example.com",
  "country": "Iran"
}
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Response:

[
  { "id": 1, "first_name": "Hediyeh", "last_name": "Karimi", "age": 28, "email": "hediyeh.karimi@example.com", "country": "Iran" },
  { "id": 2, "first_name": "Ali", "last_name": "Rezaei", "age": 20, "email": "ali.rezaei@example.com", "country": "Iran" },
  { "id": 6, "first_name": "Sara", "last_name": "Ahmadi", "age": 25, "email": "sara.ahmadi@example.com", "country": "Iran" }
]
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3.4 Update a User

Request:


PUT https://codenxa.leanea.com/hediyeh/users/put/2
Content-Type: application/json
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Body:

{
  "age": 21,
  "email": "ali.new@example.com"
}
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Response:

[
  { "id": 1, "first_name": "Hediyeh", "last_name": "Karimi", "age": 28, "email": "hediyeh.karimi@example.com", "country": "Iran" },
  { "id": 2, "first_name": "Ali", "last_name": "Rezaei", "age": 21, "email": "ali.new@example.com", "country": "Iran" }
]
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3.5 Delete a User

Request:

DELETE https://codenxa.leanea.com/hediyeh/users/delete/4
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Response (remaining users):

[
  { "id": 1, "first_name": "Hediyeh", "last_name": "Karimi", "age": 28, "email": "hediyeh.karimi@example.com", "country": "Iran" },
  { "id": 2, "first_name": "Ali", "last_name": "Rezaei", "age": 20, "email": "ali.rezaei@example.com", "country": "Iran" }
]
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4.API Calling (Consuming APIs)

Besides making APIs, Node-RED can also consume external APIs (call them like a client).
This is done with the HTTP Request node.

Basic flow:

Inject → HTTP Request → Debug
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4.1 Example: Calling a Public API

Request

Suppose we want to call the JSONPlaceholder
fake API to get user info:

GET https://jsonplaceholder.typicode.com/users/1
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Node-RED Flow

Inject node → triggers the request

HTTP Request node → configured with the API URL

Debug node → shows the response

Response
{
  "id": 1,
  "name": "Leanne Graham",
  "username": "Bret",
  "email": "Sincere@april.biz",
  "address": {
    "city": "Gwenborough",
    "zipcode": "92998-3874"
  }
}
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4.2 Example: Calling an Internal API (Inside Node-RED)

You can also use Node-RED’s HTTP Request node to call APIs you created in Node-RED itself.

For example, if you already built a User API (/users/GetAll), you can call it from another flow:

Request

GET https://codenxa.leanea.com/hediyeh/users/GetAll
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Node-RED Flow

Inject node → starts the request
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HTTP Request node → configured with https://codenxa.leanea.com/hediyeh/users/GetAll

Debug node → shows the result

Response (from your own Node-RED API)

{
  "users": [
    {
      "id": 1,
      "age": 28,
      "first_name": "Hediyeh",
      "last_name": "Karimi",
      "email": "hediyeh.karimi@example.com",
      "country": "Iran"
    },
    {
      "id": 2,
      "age": 20,
      "first_name": "Ali",
      "last_name": "Rezaei",
      "email": "ali.rezaei@example.com",
      "country": "Iran"
    }
  ]
}
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Note:

External APIs (like JSONPlaceholder, weather APIs, payment APIs).

Internal APIs (APIs you built inside Node-RED).

5. Difference Between Making vs. Calling APIs

Making API (Server role) Calling API (Client role)
Node-RED creates endpoints (like /users/...) Node-RED sends requests to endpoints
Uses HTTP In + Function + HTTP Response Uses Inject + HTTP Request + Debug
Responds to external clients (Postman, apps, etc.) Fetches data from external services (APIs)
Node-RED behaves as a server Node-RED behaves as a client

6. When to Use What?

Making API → When you want others to use your system (e.g., CRUD on your user database).

Calling API → When you need data from external systems (e.g., weather API, payment gateway, external DB).

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