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References
CPS-989
-
Getting issue details...
STATUS
Medium article
Issues & Decisions
Overview
As specified in the Jira ticket the replacement of RestTemplate became neccessary due the fact that it is not under development anymore and also because it does not support basic function required in the modern dev world such as async calls.
Blocking vs Non-Blocking Client
RestTemplate is a blocking clinet. Which means that an HTTP request will use a thread as long as the request is pending/finishes (thread-per-request model).
This means that a thread will use an extra amount of memory and CPU resource that could lead to performance degradation.
WebClient at the other hand is based on the Spring Reactive framework which provides capability to non-blocking async calls thanks to it's event-driven architecture. Because of this WebClient uses less resources (threads, memory).
Example configuration
@Slf4j
@Configuration
@AllArgsConstructor
public class WebClientConfiguration {
public static final int TIMEOUT = 2000;
private final DmiConfiguration.SdncProperties sdncProperties;
@Bean
public WebClient webClient() {
final var httpClient = HttpClient.create()
.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, TIMEOUT) // millis
.doOnConnected(connection ->
connection
.addHandlerLast(new ReadTimeoutHandler(TIMEOUT, TimeUnit.MILLISECONDS)) // millis
.addHandlerLast(new WriteTimeoutHandler(TIMEOUT, TimeUnit.MILLISECONDS))); //millis
return WebClient.builder()
.baseUrl(sdncProperties.getBaseUrl())
.defaultHeaders(header -> header.set(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE))
.defaultHeaders(header -> header.setBasicAuth(sdncProperties.getAuthUsername(), sdncProperties.getAuthPassword()))
.clientConnector(new ReactorClientHttpConnector(httpClient))
.filter(logRequest())
.filter(logResponse())
.build();
}
private ExchangeFilterFunction logRequest() {
return (clientRequest, next) -> {
log.info("Request: {} {}", clientRequest.method(), clientRequest.url());
log.info("--- Http Headers: ---");
clientRequest.headers().forEach(this::logHeader);
log.info("--- Http Cookies: ---");
clientRequest.cookies().forEach(this::logHeader);
return next.exchange(clientRequest);
};
}
private ExchangeFilterFunction logResponse() {
return ExchangeFilterFunction.ofResponseProcessor(clientResponse -> {
log.info("Response: {}", clientResponse.statusCode());
clientResponse.headers().asHttpHeaders()
.forEach((name, values) -> values.forEach(value -> log.info("{}={}", name, value)));
return Mono.just(clientResponse);
});
}
private void logHeader(String name, List values) {
values.forEach(value -> log.info("{}={}", name, value));
}
}
Sync call example
String response = webClient
.get()
.uri(resourceUrl)
.header(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
.retrieve()
.onStatus(HttpStatus::is4xxClientError,
error -> Mono.error(new RuntimeException("API not found")))
.onStatus(HttpStatus::is5xxServerError,
error -> Mono.error(new RuntimeException("Server is not responding")))
.bodyToMono(String.class)
.block();
return ResponseEntity.ok(response);
Example async call with subscribing
public Mono<String> httpOperationWithJsonData(final HttpMethod httpMethod,
final String resourceUrl,
final String jsonData,
final HttpHeaders httpHeaders) {
return webClient
.get()
.uri(resourceUrl)
.header(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
.retrieve()
.onStatus(HttpStatus::is4xxClientError,
error -> Mono.error(new RuntimeException("API not found")))
.onStatus(HttpStatus::is5xxServerError,
error -> Mono.error(new RuntimeException("Server is not responding")))
.bodyToMono(String.class);
}
httpOperationWithJsonDataAsync(HttpMethod.GET, getResourceUrl, null, httpHeaders)
.subscribe(response -> {
log.info("Get async response : {}", response);
responseEntity.getBody().concat(response);
});