一、介绍

1.1、RestTemplate 

同步阻塞代码，http 请求返回响应才继续执行。

1.2、WebClient 

1.基于 Reactor 和 Netty。

2.响应式 web 客户端。异步执行不阻塞代码，少量的线程数处理高并发的 Http 请求。

3.集成 Spring WebFlux 框架，可与其他 Spring 组件无缝协作。

4.可通过自定义 ExchangeFilterFunction 对请求和响应进行拦截和处理。

二、使用 

2.1、引入依赖 

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

2.2、基础属性介绍

2.2.1、基础配置

HTTP 底库// 选择 HTTP 底库; 默认底层用Netty，切换Jetty。WebClient .builder() .clientConnector(new JettyClientHttpConnector()) .build();全局的请求配置// 设置基础的全局的web请求配置，如cookie、header、baseUrl。WebClient.builder().defaultCookie("kl","kl").defaultUriVariables(ImmutableMap.of("name","kl")).defaultHeader("header","kl").defaultHeaders(httpHeaders -> {httpHeaders.add("header1","kl");httpHeaders.add("header2","kl");}).defaultCookies(cookie ->{cookie.add("cookie1","kl");cookie.add("cookie2","kl");}).baseUrl("http://www.kailing.pub").build();Filter// Filter 过滤器，统一修改拦截请求。WebClient.builder().baseUrl("http://www.kailing.pub").filter((request, next) -> {ClientRequest filtered = ClientRequest.from(request).header("foo", "bar").build();return next.exchange(filtered);}).filters(filters ->{filters.add(ExchangeFilterFunctions.basicAuthentication("username","password"));filters.add(ExchangeFilterFunctions.limitResponseSize(800));}).build().get().uri("/article/index/arcid/{id}.html", 254).retrieve().bodyToMono(String.class).subscribe(System.err::println);Netty 库配置 // 配置动态连接池 ConnectionProvider provider = ConnectionProvider.elastic("elastic pool"); 配置固定大小连接池，如最大连接数、连接获取超时、空闲连接死亡时间等ConnectionProvider provider = ConnectionProvider.fixed("fixed", 45, 4000, Duration.ofSeconds(6));HttpClient httpClient = HttpClient.create(provider).secure(sslContextSpec -> {SslContextBuilder sslContextBuilder = SslContextBuilder.forClient().trustManager(new File("E://server.truststore"));sslContextSpec.sslContext(sslContextBuilder);}).tcpConfiguration(tcpClient -> {// 指定Netty的 select 和 work 线程数量LoopResources loop = LoopResources.create("kl-event-loop", 1, 4, true);return tcpClient.doOnConnected(connection -> {// 读写超时设置connection.addHandlerLast(new ReadTimeoutHandler(10, TimeUnit.SECONDS)).addHandlerLast(new WriteTimeoutHandler(10));})// 连接超时设置 .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 10000) .option(ChannelOption.TCP_NODELAY, true) .runOn(loop);});WebClient.builder().clientConnector(new ReactorClientHttpConnector(httpClient)).build();

2.2.2、WebClient.builder() 的选项

uriBuilderFactory：自定义UriBuilderFactory用作基本URL(BaseUrl)。defaultHeader：每个请求的标题。defaultCookie：针对每个请求的Cookie。defaultRequest：Consumer自定义每个请求。filter：针对每个请求的客户端过滤器。exchangeStrategies：HTTP消息读取器/写入器定制。clientConnector：HTTP客户端库设置。

2.2.3、请求类型、与返回结果

.block() 阻塞当前程序等待结果.retrieve() 直接获取响应body.exchange() 可访问整个ClientResponse

2.3、get 请求

// 简单传参。默认异步，通过 Mono 的 subscribe 订阅响应值。block() 阻塞当前线程获取返回值。WebClient client = WebClient.create("http://www.kailing.pub");Mono<String> result = client.get().uri("/article/arcid/{id}", 256).acceptCharset(StandardCharsets.UTF_8).accept(MediaType.TEXT_HTML).retrieve() // 同步.bodyToMono(String.class);result.subscribe(System.err::println);// 复杂传参 — MultiValueMap。默认异步，通过 Mono 的 subscribe 订阅响应值。block() 阻塞当前线程获取返回值。MultiValueMap<String, String> params = new LinkedMultiValueMap<>();params.add("name", "kl");params.add("age", "19");// 定义 url 参数 Map<String, Object> uriVariables = new HashMap<>(); uriVariables.put("id", 200);String uri = UriComponentsBuilder.fromUriString("/article/arcid/{id}").queryParams(params).uriVariables(uriVariables).toUriString();Mono<String> result = client.get().uri(uri).acceptCharset(StandardCharsets.UTF_8).accept(MediaType.TEXT_HTML).retrieve().bodyToMono(String.class);result.subscribe(System.err::println);// 复杂传参 — UriBuilder。默认异步，通过 Mono 的 subscribe 订阅响应值。block() 阻塞当前线程获取返回值。Mono<String> resp = WebClient.create().get().uri(uriBuilder -> uriBuilder.scheme("http").host("www.baidu.com").path("/s").queryParam("wd", "北京天气").queryParam("other", "test").build()).retrieve().bodyToMono(String.class);

2.4、post 请求

// 表单 默认异步，通过 Mono 的 subscribe 订阅响应值。block() 阻塞当前线程获取返回值。MultiValueMap<String, String> formData = new LinkedMultiValueMap<>();formData.add("name1","value1");formData.add("name2","value2");Mono<String> resp = WebClient.create().post().uri("http://www.w3school.com.cn/test/demo_form.asp").contentType(MediaType.APPLICATION_FORM_URLENCODED).body(BodyInserters.fromFormData(formData)).retrieve().bodyToMono(String.class);LOGGER.info("result:{}",resp.block());// FormInserter 表单：参数、文件。默认异步，通过 Mono 的 subscribe 订阅响应值。block() 阻塞当前线程获取返回值。WebClient client = WebClient.create("http://www.kailing.pub");FormInserter formInserter = fromMultipartData("name","kl").with("age",19).with("map",ImmutableMap.of("xx","xx")).with("file",new File("C://xxx.doc"));Mono<String> result = client.post().uri("/article/index/arcid/{id}.html", 256).contentType(MediaType.APPLICATION_JSON).body(formInserter)//.bodyValue(ImmutableMap.of("name","kl")).retrieve().bodyToMono(String.class);result.subscribe(System.err::println);// json — 实体类。默认异步，通过 Mono 的 subscribe 订阅响应值。block() 阻塞当前线程获取返回值。User user = new User();user.setName("aaa");user.setTitle("AAAAAA");Mono<String> resp = WebClient.create() .post().uri("http://localhost:8080/demo/json").contentType(MediaType.APPLICATION_JSON_UTF8).body(Mono.just(user),User.class).retrieve().bodyToMono(String.class);System.out.println("---resp.block(): "+resp.block());// json — raw。默认异步，通过 Mono 的 subscribe 订阅响应值。block() 阻塞当前线程获取返回值。Mono<String> resp = WebClient.create().post().uri("http://localhost:8080/demo/json").contentType(MediaType.APPLICATION_JSON_UTF8).body(BodyInserters.fromObject("{\n" +" \"title\" : \"this is title\",\n" +" \"author\" : \"this is author\"\n" +"}")).retrieve().bodyToMono(String.class);System.out.println("---resp.block(): "+resp.block());// 二进制上传文件HttpHeaders headers = new HttpHeaders();headers.setContentType(MediaType.IMAGE_PNG);HttpEntity<ClassPathResource> entity = new HttpEntity<>(new ClassPathResource("parallel.png"), headers);MultiValueMap<String, Object> parts = new LinkedMultiValueMap<>();parts.add("file", entity);Mono<String> resp = WebClient.create().post().uri("http://localhost:8080/upload").contentType(MediaType.MULTIPART_FORM_DATA).body(BodyInserters.fromMultipartData(parts)).retrieve().bodyToMono(String.class);System.out.println("---resp.block(): "+resp.block());

2.5、WebSocketClient  使用 Socket

WebSocketClient client = new ReactorNettyWebSocketClient();URI url = new URI("ws://localhost:8080/path");client.execute(url, session ->session.receive().doOnNext(System.out::println).then());

三、封装工具类 

import org.springframework.http.HttpHeaders;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 class WebClientUtils { private WebClient webClient; public WebClientUtils(String baseUrl) { this.webClient = WebClient.builder() .baseUrl(baseUrl) .defaultHeader(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE).filter(logRequest()) .build(); } public <T> Mono<T> get(String uri, Class<T> responseType) { return webClient.get() .uri(uri) .retrieve() .bodyToMono(responseType); } public <T> Mono<T> post(String uri, Object request, Class<T> responseType) { return webClient.post() .uri(uri) .body(BodyInserters.fromValue(request)) .retrieve() .bodyToMono(responseType); } public <T> Mono<T> put(String uri, Object request, Class<T> responseType) { return webClient.put() .uri(uri) .body(BodyInserters.fromValue(request)) .retrieve() .bodyToMono(responseType); } public <T> Mono<T> delete(String uri, Class<T> responseType) { return webClient.delete() .uri(uri) .retrieve() .bodyToMono(responseType); }private ExchangeFilterFunction logRequest() { return (clientRequest, next) -> { logger.info("Request: {} {}", clientRequest.method(), clientRequest.url());clientRequest.headers().forEach((name, values) -> values.forEach(value -> logger.info("{}={}", name, value))); return next.exchange(clientRequest);};}}public class Test001 { public static void main(String[] args) { WebClientUtils webClientUtils = new WebClientUtils("https://api.example.com"); // 发起 GET 请求 webClientUtils.get("/users/1", User.class).subscribe(user -> System.out.println("GET response: " + user)); // 发起 POST 请求 User newUser = new User("John", "Doe"); webClientUtils.post("/users", newUser, User.class).subscribe(user -> System.out.println("POST response: " + user)); // 发起 PUT 请求 User updatedUser = new User("Jane", "Doe"); webClientUtils.put("/users/1", updatedUser, User.class).subscribe(user -> System.out.println("PUT response: " + user)); // 发起 DELETE 请求 webClientUtils.delete("/users/1", Void.class).subscribe(response -> System.out.println("DELETE response: " + response)); }}