还在使用 RestTemplate？来了解一下官方推荐的 WebClient ！
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2023-10-16 10:36
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「非阻塞 I/O」：WebClient 构建在 Reactor 之上，它提供了一种非阻塞、反应式的方法来处理 I/O。这可以在高流量应用程序中实现更好的可扩展性和更高的性能。 -
「函数式风格」：WebClient 使用函数式编程风格，可以使代码更易于阅读和理解。它还提供了流畅的 API，可以更轻松地配置和自定义请求。 -
「更好地支持流式传输」：WebClient 支持请求和响应正文的流式传输，这对于处理大文件或实时数据非常有用。 -
「改进的错误处理」：WebClient 提供比 RestTemplate 更好的错误处理和日志记录，从而更轻松地诊断和解决问题。
设置请求超时不会有任何影响
❝ 让我们看看如何在 SpringBoot 3 应用程序中使用 WebClient。 ❞
(1) 创建网络客户端：
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();
(2) 同步发送请求（就像RestTemplate一样）
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;
}
(3) 异步发送请求：
import org.springframework.http.MediaType;
import org.springframework.web.reactive.function.BodyInserters;
import org.springframework.web.reactive.function.client.WebClient;
import reactor.core.publisher.Mono;
public static Mono<String> 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);
}
❝ 请注意，在此示例中，WebClient是使用默认配置构建的。你可能需要根据不同要求进行不同的配置。 另请注意，block()用于同步等待响应，这可能并不适合所有情况。你可能需要考虑subscribe()异步使用和处理响应。 ❞
makePostRequestAsync( "https://example.com/api" , "param1=value1¶m2=value2" )
.subscribe(response -> {
// 处理响应
System.out.println ( response );
}, error -> {
/ / 处理错误
System.err.println ( error .getMessage ());
}
);
(4) 处理4XX和5XX错误：
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.web.reactive.function.BodyInserters;
import org.springframework.web.reactive.function.client.WebClient;
import reactor.core.publisher.Mono;
public static Mono<String> makePostRequestAsync(String url, String postData) {
WebClient webClient = WebClient.builder()
.baseUrl(url)
.build();
return webClient.post()
.uri("/")
.contentType(MediaType.APPLICATION_FORM_URLENCODED)
.body(BodyInserters.fromFormData("data", postData))
.retrieve()
.onStatus(HttpStatus::is4xxClientError, clientResponse -> Mono.error(new RuntimeException("Client error")))
.onStatus(HttpStatus::is5xxServerError, clientResponse -> Mono.error(new RuntimeException("Server error")))
.bodyToMono(String.class);
}
-
aPredicate确定错误状态代码是否与条件匹配 -
aFunction用于返回Mono，即要传播到订阅者的错误信息。
(5) 根据错误状态采取行动：
makePostRequestAsync("https://example.com/api", "param1=value1¶m2=value2")
.subscribe(response -> {
// handle the response
System.out.println(response);
}, error -> {
// handle the error
System.err.println("An error occurred: " + error.getMessage());
if (error instanceof WebClientResponseException) {
WebClientResponseException webClientResponseException = (WebClientResponseException) error;
int statusCode = webClientResponseException.getStatusCode().value();
String statusText = webClientResponseException.getStatusText();
System.err.println("Error status code: " + statusCode);
System.err.println("Error status text: " + statusText);
}
});
(6) 处理成功响应和错误的完整代码：
responseMono.subscribe(
response -> {
// handle the response
LOG.info("SUCCESS API Response {}", response);
},
error -> {
// handle the error
LOG.error("An error occurred: {}", error.getMessage());
LOG.error("error class: {}", error.getClass());
// Errors / Exceptions from Server
if (error instanceof WebClientResponseException) {
WebClientResponseException webClientResponseException =
(WebClientResponseException) error;
int statusCode = webClientResponseException.getStatusCode().value();
String statusText = webClientResponseException.getStatusText();
LOG.info("Error status code: {}", statusCode);
LOG.info("Error status text: {}", statusText);
if (statusCode >= 400 && statusCode < 500) {
LOG.info(
"Error Response body {}", webClientResponseException.getResponseBodyAsString());
}
Throwable cause = webClientResponseException.getCause();
LOG.error("webClientResponseException");
if (null != cause) {
LOG.info("Cause {}", cause.getClass());
if (cause instanceof ReadTimeoutException) {
LOG.error("ReadTimeout Exception");
}
if (cause instanceof TimeoutException) {
LOG.error("Timeout Exception");
}
}
}
// Client errors i.e. Timeouts etc -
if (error instanceof WebClientRequestException) {
LOG.error("webClientRequestException");
WebClientRequestException webClientRequestException =
(WebClientRequestException) error;
Throwable cause = webClientRequestException.getCause();
if (null != cause) {
LOG.info("Cause {}", cause.getClass());
if (cause instanceof ReadTimeoutException) {
LOG.error("ReadTimeout Exception");
}
if (cause instanceof ConnectTimeoutException) {
LOG.error("Connect Timeout Exception");
}
}
}
});
超时：
return webClient
.method(this.httpMethod)
.uri(this.uri)
.headers(httpHeaders -> httpHeaders.addAll(additionalHeaders))
.bodyValue(this.requestEntity)
.retrieve()
.bodyToMono(responseType)
.timeout(Duration.ofMillis(readTimeout)) // request timeout for this request
.block();
结论
本文为翻译文，来源：https://medium.com
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