Handling Request and Response Streams in WebClient

In the world of reactive programming, where non-blocking, asynchronous operations are crucial for building scalable and efficient applications, Spring Web Flux provides a powerful WebClient class that allows us to consume and produce streams of data for HTTP requests and responses. In this article, we will explore how to handle request and response streams in WebClient.

Sending Request Streams

To send a request stream, we can use the body(BodyInserter<?, ? super ClientHttpRequest>) method of WebClient. This method takes a BodyInserter object as its parameter, which can be used to insert the request body.

To create a request stream, we can use the BodyInserters.fromPublisher(Publisher<? extends T>, Class<T>) method, where the first parameter is the Publisher that emits the data elements of the stream, and the second parameter is the class of the elements in the stream.

Here's an example of how to send a request stream with WebClient:

Publisher<MyObject> dataStream = getDataStream(); // Publisher that emits data elements
webClient.post()
    .uri("/api/my-endpoint")
    .body(BodyInserters.fromPublisher(dataStream, MyObject.class))
    .retrieve()
    .bodyToMono(Void.class)
    .subscribe();

In the above example, we first obtain a Publisher called dataStream, which emits data elements of type MyObject. Then, using the body() method, we create a request stream by passing BodyInserters.fromPublisher(dataStream, MyObject.class) as the parameter. Finally, we invoke the retrieve() method to send the request.

Handling Response Streams

To handle a response stream, WebClient provides the bodyToFlux(Class<T>) method, which returns a Flux that emits the data elements of the response stream.

Here's an example of how to handle a response stream with WebClient:

Flux<MyObject> responseStream = webClient.get()
    .uri("/api/my-endpoint")
    .retrieve()
    .bodyToFlux(MyObject.class);

responseStream.subscribe(myObject -> {
    // Process each data element of the response stream
});

In the above example, we use the bodyToFlux() method to convert the response stream into a Flux of MyObject elements. Then, we subscribe to the Flux and process each data element received from the response stream.

Summary

WebClient in Spring Web Flux provides convenient methods for handling request and response streams. By using body(BodyInserter<?, ? super ClientHttpRequest>) to send request streams and bodyToFlux(Class<T>) to handle response streams, we can efficiently work with streams of data in a reactive and non-blocking manner.

Being familiar with handling request and response streams in WebClient is essential when building reactive applications that require efficient data streaming. With its powerful features and intuitive APIs, WebClient allows us to embrace the reactive paradigm and build high-performance applications that can handle large amounts of data effectively.