Spring WebFlux : WebClient + Fallback on error - spring

Question

I want to set up a fallback when my program works if the first service is unavailable.
On the second service, I use WebClient which accesses the first service and receives data from it.
I made two options but they do not work for me.
If both services are alive, then everything works well.
If the first service is unavailable, then when I try to send a request via WebClient, nothing happens, I see a blank screen in the browser.
1) The first option:
#Service
public class WebClientService {
private static final String API_MIME_TYPE = "application/json";
private static final String API_BASE_URL = "http://localhost:8081";
private static final String USER_AGENT = "User Service";
private static final Logger logger = LoggerFactory.getLogger(WebClientService.class);
private WebClient webClient;
public WebClientService() {
this.webClient = WebClient.builder()
.baseUrl(API_BASE_URL)
.defaultHeader(HttpHeaders.CONTENT_TYPE, API_MIME_TYPE)
.defaultHeader(HttpHeaders.USER_AGENT, USER_AGENT)
.filter(WebClientService.errorHandlingFilter())
.build();
}
public Flux<Bucket> getDataByWebClient() {
return webClient
.get()
.uri("/getAll")
.exchange()
.flatMapMany(clientResponse -> clientResponse.bodyToFlux(Bucket.class));
}
public static ExchangeFilterFunction errorHandlingFilter() {
return ExchangeFilterFunction.ofResponseProcessor(clientResponse -> {
if(clientResponse.statusCode()!=null && (clientResponse.statusCode().is5xxServerError() || clientResponse.statusCode().is4xxClientError()) ) {
return clientResponse.bodyToMono(String.class)
.flatMap(errorBody -> {
return Mono.error(new MyCustomServerException());
});
}else {
return Mono.just(clientResponse);
}
});
}
}
Class MyCustomServerException
public class MyCustomServerException extends Throwable {
public String getAllEmployeesList() {
return "Server error";
}
public MyCustomServerException() {
getAllEmployeesList();
}
}
2) The second option:
#Service
public class WebClientService {
private static final String API_MIME_TYPE = "application/json";
private static final String API_BASE_URL = "http://localhost:8081";
private static final String USER_AGENT = "User Service";
private static final Logger logger = LoggerFactory.getLogger(WebClientService.class);
private WebClient webClient;
public WebClientService() {
this.webClient = WebClient.builder()
.baseUrl(API_BASE_URL)
.defaultHeader(HttpHeaders.CONTENT_TYPE, API_MIME_TYPE)
.defaultHeader(HttpHeaders.USER_AGENT, USER_AGENT)
.build();
}
public Flux<Bucket> getDataByWebClient() {
return webClient
.get()
.uri("/stream/buckets/delay")
.exchange()
.flatMapMany(clientResponse -> clientResponse.bodyToFlux(Bucket.class));
}
public Flux<Bucket> getDataByWebClient() {
return webClient
.get()
.uri("/getAll")
.retrieve()
.onStatus(HttpStatus::is4xxClientError, response -> {
System.out.println("4xx eror");
return Mono.error(new RuntimeException("4xx"));
})
.onStatus(HttpStatus::is5xxServerError, response -> {
System.out.println("5xx eror");
return Mono.error(new RuntimeException("5xx"));
})
.onStatus(HttpStatus::isError, clientResponse -> {
System.out.println("eror");
return Mono.error(new MyCustomServerException());
})
.bodyToFlux(Bucket.class);
}
}
Why is this not working? Can anyone tell me?
I want the browser to display the message "Server error" from my class with an error.
Thanks!