Spring Webclient : Non-blocking, reactive client to perform HTTP operations

• Webclient provide asynchronous,non-blocking way to communicate with different system using http operations .
• This is not replacement for RestTemplate however its to improve performance of operations and avoid blocking thread to wait for response .
• Webclient fires the operation and does not wait for response which make the call reactive and process the response when its received .

Asynchronous web frameworks apply event looping to handle more requests with fewer threads.

Maven Dependency

<dependency> 
<groupId>org.springframework.boot</groupId> 
<artifactId>spring-boot-starter-webflux</artifactId> 
</dependency>

Code Implementation:

• GET:

UriCimponenets uriComponents =UriComponentsBuilds.fromHttpUrl(“http://endpoint/{param}")
 .buildAndExpand(inputParam);
HttpHeaders headers= new HttpHeaders ();
Webclient webclient;
String response=webclient.method(HttpMethod.GET)
      .uri (uriComponents.toUri())
      .headers(httpHeaders-> {
               httpHeaders.add(“key”,”value”);
                })
      .contentType(MediaType.APPLICATION_JSON)
      .retrieve()
      .onStatus(status-> status.is4xxClientError||                  status.5xxClientError(),
             clientResponse->             {clientResponse.bodyToMono(String.class).subscriber(errorBody->log.error(error.Body));
               return Mono.Error(new                  ResponseStatusException(clientResponse.statusCode()));
          }) 
      .bodyToMono(String.class)
      .doOnSuccess(clientResposne -> { log.info(“Response:       {}”,clientResponse)})
      .block(Duration,ofSeconds(50));

POST:

UriCimponenets uriComponents =UriComponentsBuilds.fromHttpUrl(“http://endpoint/{param}")
 .buildAndExpand(inputParam);
HttpHeaders headers= new HttpHeaders ();
Webclient webclient;
//post response status of operation .
String response=webclient.method(HttpMethod.POST)
      .uri (uriComponents.toUri())
      .headers(httpHeaders-> {
               httpHeaders.add(“key”,”value”);
                })
      .contentType(MediaType.APPLICATION_JSON)
      .body(BodyInserters.fromValue(<jsonStringBody>))
      .exchange()
      .flatMap(clientResponse -> {
           if(clientResponse.statusCode().is4xxClientError())
              {
             clientResponse->             {clientResponse.bodyToMono(String.class).subscriber(errorBody->log.error(error.Body));
    return Mono.Error(new                  ResponseStatusException(clientResponse.statusCode()));
             }
           else 
             return clientResponse.bodyToMono(String.class);                           })
      .doOnSuccess(clientResposne -> { log.info(“Response:       {}”,clientResponse)})
      .block(Duration,ofSeconds(50));

ref# https://livebook.manning.com/book/spring-in-action-fifth-edition/chapter-11/v-7/33