Using Spring WebClient Instead of RestTemplate: Advantages and Code Examples

In Spring Framework 5+ RestTemplate is deprecated and WebClient is recommended for new projects.

WebClient offers non‑blocking I/O built on Reactor, a functional programming style, better streaming support, and improved error handling.

Creating a WebClient example:

import io.netty.channel.ChannelOption;
import io.netty.channel.ConnectTimeoutException;
import io.netty.handler.timeout.ReadTimeoutException;
import io.netty.handler.timeout.ReadTimeoutHandler;
import io.netty.handler.timeout.TimeoutException;
import jakarta.annotation.PostConstruct;
import java.time.Duration;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.http.HttpMethod;
import org.springframework.http.MediaType;
import org.springframework.http.client.reactive.ReactorClientHttpConnector;
import org.springframework.stereotype.Service;
import org.springframework.web.reactive.function.client.WebClient;
import org.springframework.web.reactive.function.client.WebClientRequestException;
import org.springframework.web.reactive.function.client.WebClientResponseException;
import reactor.core.publisher.Mono;
import reactor.netty.http.client.HttpClient;

HttpClient httpClient = HttpClient.create()
        .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, connectionTimeout)
        .responseTimeout(Duration.ofMillis(requestTimeout))
        .doOnConnected(conn -> conn.addHandlerLast(new ReadTimeoutHandler(readTimeout)));

WebClient client = WebClient.builder()
        .clientConnector(new ReactorClientHttpConnector(httpClient))
        .build();

Synchronous request (similar to RestTemplate) :

public String postSynchronously(String url, String requestBody) {
    LOG.info("Going to hit API - URL {} Body {}", url, requestBody);
    String response = "";
    try {
        response = client.method(HttpMethod.POST)
                .uri(url)
                .accept(MediaType.ALL)
                .contentType(MediaType.APPLICATION_JSON)
                .bodyValue(requestBody)
                .retrieve()
                .bodyToMono(String.class)
                .block();
    } catch (Exception ex) {
        LOG.error("Error while calling API ", ex);
        throw new RuntimeException("XYZ service api error: " + ex.getMessage());
    } finally {
        LOG.info("API Response {}", response);
    }
    return response;
}

Asynchronous request using Mono:

public static Mono
makePostRequestAsync(String url, String postData) {
    WebClient webClient = WebClient.builder().build();
    return webClient.post()
            .uri(url)
            .contentType(MediaType.APPLICATION_FORM_URLENCODED)
            .body(BodyInserters.fromFormData("data", postData))
            .retrieve()
            .bodyToMono(String.class);
}

Errors can be handled with onStatus for 4xx/5xx responses and by inspecting exceptions in subscribe callbacks.

Timeouts can be set per request with .timeout(Duration.ofMillis(readTimeout)) , while connection timeout is configured once when building the client.

Conclusion: migrating to WebClient provides non‑blocking performance, richer error handling, and streaming capabilities, and it can still be used in a blocking style when needed.