Angular HTTP Interceptors

HTTP interceptors in Angular are a powerful tool for handling HTTP requests and responses. They allow you to modify the request or response before they are sent or received, and can be used for a variety of tasks such as adding authentication headers, handling errors, or logging requests.

Interceptors are implemented using the HttpInterceptor interface in Angular. You can create a new interceptor by implementing this interface and providing it to the HTTP_INTERCEPTORS multi-provider in your application module.

Creating an Interceptor

To create a new interceptor, you first need to create a class that implements the HttpInterceptor interface. This interface requires you to implement a intercept method that takes an HttpRequest object and a HttpHandler object as parameters.

Within the intercept method, you can modify the request, for example by adding headers or changing the URL, and then pass the modified request to the handle method of the HttpHandler object to send the request to the server.

Registering the Interceptor

Once you have created your interceptor class, you need to register it with the application module. You can do this by providing it to the HTTP_INTERCEPTORS multi-provider, which allows you to provide multiple interceptors to the application.

Here’s an example of how you might register an interceptor in your application module:


import { HTTP_INTERCEPTORS } from '@angular/common/http';
import { MyInterceptor } from './my-interceptor';

@NgModule({
...
providers: [
{ provide: HTTP_INTERCEPTORS, useClass: MyInterceptor, multi: true }
],
...
})


Using Interceptors

Once you have registered an interceptor, it will automatically be called for every HTTP request made by your application. This allows you to centralize logic for handling requests and responses, and makes it easy to implement cross-cutting concerns such as logging or authentication.

Overall, HTTP interceptors in Angular are a powerful tool for managing HTTP requests and responses in your application. They allow you to centralize logic for handling requests and responses, and provide a flexible way to modify and augment HTTP requests and responses.