Consuming and integrating with external reactive APIs

In the world of asynchronous programming, reactive APIs have gained quite a reputation for improving performance and scalability. As a developer working with Spring Web Flux, you can take advantage of these APIs to consume and integrate external services seamlessly.

What are reactive APIs?

Reactive APIs follow the principles of reactive programming, which is all about building systems that react to events and asynchronous data streams. These APIs provide non-blocking calls, allowing your application to perform other tasks while waiting for a response.

Consuming reactive APIs in Spring Web Flux

Spring Web Flux provides a powerful and flexible client for consuming reactive APIs. To start consuming an external reactive API, you first need to define the endpoint and the expected response type. Let's take a look at an example:

public Mono<User> getUserById(String id) {
   WebClient client = WebClient.create("");
   return client.get()
                .uri("/users/{id}", id)

In the above example, we create a WebClient instance pointing to the base URL of the external API. Then, we make a GET request to the /users/{id} endpoint, where {id} is the placeholder for the user's ID. Finally, we retrieve and parse the response body into a Mono<User>.

You can subscribe to this Mono<User> and process the result asynchronously. If you want to handle errors or add additional requests, you can use operators like onErrorResume, flatMap, or concatMap.

Integrating reactive APIs with Spring Web Flux

Integrating external reactive APIs with Spring Web Flux is equally straightforward. You can leverage the reactive programming model to handle events and data streams from multiple sources efficiently.

For example, let's imagine an application that integrates with two social media platforms, Twitter and Facebook. We want to retrieve the latest posts from both platforms and present them to the users. Here's how we can accomplish this:

public Flux<Post> getLatestPosts() {
   WebClient twitterClient = WebClient.create("");
   WebClient facebookClient = WebClient.create("");
   Flux<Post> twitterPosts = twitterClient.get()
   Flux<Post> facebookPosts = facebookClient.get()
   return Flux.merge(twitterPosts, facebookPosts);

In this example, we create two WebClient instances for Twitter and Facebook APIs. We then make GET requests to retrieve the latest posts from each platform and parse the response into Flux<Post>. Finally, we merge both fluxes using the merge() operator to obtain a single stream of posts from both platforms.

By leveraging reactive APIs, you can retrieve and integrate data from multiple sources in an asynchronous and non-blocking manner, making your application more efficient and responsive.


Consuming and integrating with external reactive APIs is a fundamental aspect of building modern, scalable applications. With Spring Web Flux, it's a breeze to consume reactive APIs using WebClient and benefit from the power of reactive programming.

By leveraging reactive APIs and the reactive programming model, you can design high-performance systems that handle multiple asynchronous events and data streams efficiently. With Spring Web Flux, you are well-equipped to tackle even the most demanding integration challenges.

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