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之前写了一篇restTemplate使用实例，由于spring 5全面引入reactive，同时也有了restTemplate的reactive版webclient，本文就来对应展示下webclient的基本使用。

请求携带header

• 携带cookie

	@Testpublic void testWithCookie(){Mono<String> resp = WebClient.create().method(HttpMethod.GET).uri("http://baidu.com").cookie("token","xxxx").cookie("JSESSIONID","XXXX").retrieve().bodyToMono(String.class);LOGGER.info("result:{}",resp.block());}

• 携带basic auth

    @Testpublic void testWithBasicAuth(){String basicAuth = "Basic "+ Base64.getEncoder().encodeToString("user:pwd".getBytes(StandardCharsets.UTF_8));LOGGER.info(basicAuth);Mono<String> resp = WebClient.create().get().uri("http://baidu.com").header(HttpHeaders.AUTHORIZATION,basicAuth).retrieve().bodyToMono(String.class);LOGGER.info("result:{}",resp.block());}

• 设置全局user-agent

	@Testpublic void testWithHeaderFilter(){WebClient webClient = WebClient.builder().defaultHeader(HttpHeaders.USER_AGENT, "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36").filter(ExchangeFilterFunctions.basicAuthentication("user","password")).filter((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);}).build();Mono<String> resp = webClient.get().uri("https://baidu.com").retrieve().bodyToMono(String.class);LOGGER.info("result:{}",resp.block());}

get请求

• 使用placeholder传递参数

	@Testpublic void testUrlPlaceholder(){Mono<String> resp = WebClient.create().get()//多个参数也可以直接放到map中,参数名与placeholder对应上即可.uri("http://www.baidu.com/s?wd={key}&other={another}","北京天气","test") //使用占位符.retrieve().bodyToMono(String.class);LOGGER.info("result:{}",resp.block());}

• 使用uriBuilder传递参数

    @Testpublic void testUrlBiulder(){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);LOGGER.info("result:{}",resp.block());}

post表单

	@Testpublic void testFormParam(){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());}

post json

• 使用bean来post

static class Book {String name;String title;public String getName() {return name;}public void setName(String name) {this.name = name;}public String getTitle() {return title;}public void setTitle(String title) {this.title = title;}}@Testpublic void testPostJson(){Book book = new Book();book.setName("name");book.setTitle("this is title");Mono<String> resp = WebClient.create().post().uri("http://localhost:8080/demo/json").contentType(MediaType.APPLICATION_JSON_UTF8).body(Mono.just(book),Book.class).retrieve().bodyToMono(String.class);LOGGER.info("result:{}",resp.block());}

• 直接post raw json

	@Testpublic void testPostRawJson(){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);LOGGER.info("result:{}",resp.block());}

post二进制--上传文件

	@Testpublic void testUploadFile(){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);LOGGER.info("result:{}",resp.block());}

下载二进制

• 下载图片

	@Testpublic void testDownloadImage() throws IOException {Mono<Resource> resp = WebClient.create().get().uri("http://www.toolip.gr/captcha?complexity=99&size=60&length=9").accept(MediaType.IMAGE_PNG).retrieve().bodyToMono(Resource.class);Resource resource = resp.block();BufferedImage bufferedImage = ImageIO.read(resource.getInputStream());ImageIO.write(bufferedImage, "png", new File("captcha.png"));}

• 下载文件

	@Testpublic void testDownloadFile() throws IOException {Mono<ClientResponse> resp = WebClient.create().get().uri("http://localhost:8080/file/download").accept(MediaType.APPLICATION_OCTET_STREAM).exchange();ClientResponse response = resp.block();String disposition = response.headers().asHttpHeaders().getFirst(HttpHeaders.CONTENT_DISPOSITION);String fileName = disposition.substring(disposition.indexOf("=")+1);Resource resource = response.bodyToMono(Resource.class).block();File out = new File(fileName);FileUtils.copyInputStreamToFile(resource.getInputStream(),out);LOGGER.info(out.getAbsolutePath());}

错误处理

	@Testpublic void testRetrieve4xx(){WebClient webClient = WebClient.builder().baseUrl("https://api.github.com").defaultHeader(HttpHeaders.CONTENT_TYPE, "application/vnd.github.v3+json").defaultHeader(HttpHeaders.USER_AGENT, "Spring 5 WebClient").build();WebClient.ResponseSpec responseSpec = webClient.method(HttpMethod.GET).uri("/user/repos?sort={sortField}&direction={sortDirection}","updated", "desc").retrieve();Mono<String> mono = responseSpec.onStatus(e -> e.is4xxClientError(),resp -> {LOGGER.error("error:{},msg:{}",resp.statusCode().value(),resp.statusCode().getReasonPhrase());return Mono.error(new RuntimeException(resp.statusCode().value() + " : " + resp.statusCode().getReasonPhrase()));}).bodyToMono(String.class).doOnError(WebClientResponseException.class, err -> {LOGGER.info("ERROR status:{},msg:{}",err.getRawStatusCode(),err.getResponseBodyAsString());throw new RuntimeException(err.getMessage());}).onErrorReturn("fallback");String result = mono.block();LOGGER.info("result:{}",result);}

• 可以使用onStatus根据status code进行异常适配
• 可以使用doOnError异常适配
• 可以使用onErrorReturn返回默认值

小结

webclient是新一代的async rest template，api也相对简洁，而且是reactive的，非常值得使用。

doc

• restTemplate使用实例
• Decode ByteArray with spring 5 WebFlux framework