Spring 5 WebClient Usage Guide

sequence

Since Spring 5 has fully introduced Reactive, and the Reactive version of WebClient of restTemplate is available, this article will show the basic use of WebClient.

Request to carry header

• Carry a cookie

	@Test
    public 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());
    }
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• With basic auth

    @Test
    public 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());
    }
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• Set the global user-agent

	@Test
    public 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());
    }
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A get request

• Placeholder for passing parameters

	@Test
    public void testUrlPlaceholder(){Mono<String> resp = webClient.create ().get();"http://www.baidu.com/s?wd={key}&other={another}".Weather in Beijing."test"Retrieve ().bodytomono (string.class); LOGGER.info("result:{}",resp.block());

    }
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• Pass parameters using uriBuilder

    @Test
    public void testUrlBiulder(){
        Mono<String> resp = WebClient.create()
                .get()
                .uri(uriBuilder -> uriBuilder
                        .scheme("http")
                        .host("www.baidu.com")
                        .path("/s")
                        .queryParam("wd".Weather in Beijing)
                        .queryParam("other"."test")
                        .build())
                .retrieve()
                .bodyToMono(String.class);
        LOGGER.info("result:{}",resp.block());
    }
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Post form

	@Test
    public 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());
    }
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post json

• Use beans to 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;
        }
    }

    @Test
    public 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());
    }
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• Post raw JSON

	@Test
    public 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());
    }
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Post binary — Upload a file

	@Test
    public 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());
    }
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Download binary

• Download the pictures

	@Test
    public 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"));

    }
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• The download file

	@Test
    public 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()); }Copy the code

Error handling

	@Test
    public 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);
    }
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• You can use onStatus to perform an exception adaptation according to the Status code
• DoOnError exception adaptation can be used
• You can use onErrorReturn to return the default value

summary

Webclient is a new generation of Async REST templates, and its API is relatively simple and reactive, so it is worth using.

doc

• RestTemplate Example
• Decode ByteArray with spring 5 WebFlux framework