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| Jira | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
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Medium article
Issues & Decisions
| # | Issue | Notes | Decision |
|---|---|---|---|
| 1 |
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.
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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).
Affected classes
Apart from the *Spec files the RestTemplate is used only in 2 classes: NcmpConfiguration and DmiRestClient.
The first class configures the client while the second performs requests with RestClient.
These two classes have to be rewritten/refactored to use the WebClient.
Example configuration
| Code Block | ||||||||
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@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));
}
} |
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| Code Block | ||||||||||
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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); |
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Async call example with
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subscription
| Code Block | ||||||||
|---|---|---|---|---|---|---|---|---|
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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);
} |
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