What is HTTP Interceptor Angular ?87

 What is HTTP Interceptor Angular ?

In Angular applications, HTTP Interceptors act as powerful middleware for intercepting and transforming HTTP requests and responses before they reach their intended destinations. They offer a flexible mechanism to manipulate outgoing requests, inject headers, handle errors, modify responses, and more, providing a centralized location for common HTTP-related tasks.

Key functionalities of HTTP Interceptors:

• Request transformation: Modify outgoing requests by adding/removing headers, changing body content, or adjusting URLs based on specific logic.

• Response interception: Intercept and transform incoming responses, potentially modifying data, handling errors, or performing additional actions based on the response content.

• Error handling: Implement centralized error handling logic for failed requests, providing a consistent way to display error messages or redirect users in case of issues.

• Authorization: Inject authorization headers like access tokens or API keys into outgoing requests based on user authentication state.

• Logging and monitoring: Intercept requests and responses for logging purposes or monitoring application behavior related to HTTP communication.

Implementing HTTP Interceptors in Angular:

1. Create an Interceptor class: Define a class implementing the HttpInterceptor interface. This interface requires a intercept method that takes an HttpRequest and an HttpHandler as arguments.

2. Modify request/response: Inside the intercept method, access the HttpRequest and HttpResponse objects to perform desired transformations. Use the HttpHandler.next method to pass the modified request or response downstream in the chain.

3. Register the Interceptor: Add your custom Interceptor to the providers array in your app module or the specific feature module where you want it to apply.

Example:

TypeScript

import { Injectable } from '@angular/core';
import { HttpEvent, HttpInterceptor, HttpHandler, HttpRequest } from '@angular/common/http';
import { Observable } from 'rxjs';

@Injectable()
export class MyInterceptor implements HttpInterceptor {
  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    // Add common header
    const modifiedReq = req.clone({ setHeaders: { Authorization: 'your-token' } });
    return next.handle(modifiedReq);
  }
}

Additional Tips:

• You can create multiple Interceptors for different purposes and chain them together to achieve complex request/response handling.

• Utilize RxJS operators within the intercept method for asynchronous operations and data transformations.

• Leverage built-in Interceptors provided by Angular, like XsrfInterceptor for Cross-Site Request Forgery (CSRF) protection.

By effectively using HTTP Interceptors, you can streamline your HTTP communication logic, enhance security, improve error handling, and gain more control over how your Angular application interacts with APIs, leading to a more robust and maintainable application architecture.

Sources

1. https://medium.com/@deniscangemi/intercept-http-requests-in-angular-c6392b7b0e0

2. https://jhapriti09.medium.com/what-is-interceptor-and-how-can-implement-it-in-angular-46c40ad5952a?source=rss-------1