How to connect to a RestAPI microservice with Spring Boot WebClient

In my previous article we connected to a remote REST API using Finagle and created a CompletableFuture chain to get accounts with balance and transactions. We are using the same use-case now with WebClient to see the differences between the two options.

We can create a WebClient bean with a configurable timeout with the Java Config class below.

Our BalanceService method is quite simple now. We don’t need to use any deserialiser object and we can safely tell our webClient to transform the response from the server to our desired object. In case of 4XX/5XX we will get a WebClientException we can handle with .onStatus(predicate, function) method.

public Mono<Balance> getBalanceWebFlux(String accountId) {
    return webClient.get()
            .uri(uriBuilder -> uriBuilder
                    .path("/v2/accounts/{accountId}/balance")
                    .build(accountId))
            .retrieve()
            .bodyToMono(Balance.class);
}

I won’t add the other two services: TransactionsService and AccountService because they are very similar. We just use .bodyToFlux(Account.class) instead of the .bodyToMono method.

If you are not familiar with what a Mono is, from their JavaDoc we can understand its lifecycle. The main idea is that it can either return one value, complete with an exception, or complete without data.

On the other hand, a Flux can return many values and at some point possibly complete with an error.

To be able to get the account with its details there are 2 features we’re gonna use:

• flatMap: for Each account we trigger two…