Java11新特性之HttpClient 使用

JDK變化

1. 從java9的jdk.incubator.httpclient模塊遷移到java.net.http模塊，包名由jdk.incubator.http改爲java.net.http
2. 原來的諸如HttpResponse.BodyHandler.asString()方法變更爲HttpResponse.BodyHandlers.ofString()，變化一爲BodyHandler改爲BodyHandlers，變化二爲asXXX()之類的方法改爲ofXXX()，由as改爲of
3. 官方文檔：https://docs.oracle.com/en/java/javase/11/docs/api/java.net.http/java/net/http/package-summary.html

實例

設置超時時間

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@Test public void testTimeout() throws IOException, InterruptedException {  //1.set connect timeout  HttpClient client = HttpClient.newBuilder()    .connectTimeout(Duration.ofMillis(5000))    .followRedirects(HttpClient.Redirect.NORMAL)    .build();    //2.set read timeout  HttpRequest request = HttpRequest.newBuilder()    .uri(URI.create("http://openjdk.java.net/"))    .timeout(Duration.ofMillis(5009))    .build();    HttpResponse<String> response =    client.send(request, HttpResponse.BodyHandlers.ofString());    System.out.println(response.body());   }

HttpConnectTimeoutException實例

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Caused by: java.net.http.HttpConnectTimeoutException: HTTP connect timed out  at java.net.http/jdk.internal.net.http.ResponseTimerEvent.handle(ResponseTimerEvent.java:68)  at java.net.http/jdk.internal.net.http.HttpClientImpl.purgeTimeoutsAndReturnNextDeadline(HttpClientImpl.java:1248)  at java.net.http/jdk.internal.net.http.HttpClientImpl$SelectorManager.run(HttpClientImpl.java:877) Caused by: java.net.ConnectException: HTTP connect timed out  at java.net.http/jdk.internal.net.http.ResponseTimerEvent.handle(ResponseTimerEvent.java:69)  ... 2 more

HttpTimeoutException實例

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java.net.http.HttpTimeoutException: request timed out    at java.net.http/jdk.internal.net.http.HttpClientImpl.send(HttpClientImpl.java:559)  at java.net.http/jdk.internal.net.http.HttpClientFacade.send(HttpClientFacade.java:119)  at com.example.HttpClientTest.testTimeout(HttpClientTest.java:40)

設置authenticator

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@Test public void testBasicAuth() throws IOException, InterruptedException {  HttpClient client = HttpClient.newBuilder()    .connectTimeout(Duration.ofMillis(5000))    .authenticator(new Authenticator() {     @Override     protected PasswordAuthentication getPasswordAuthentication() {      return new PasswordAuthentication("admin","password".toCharArray());     }    })    .build();    HttpRequest request = HttpRequest.newBuilder()    .uri(URI.create("http://localhost:8080/json/info"))    .timeout(Duration.ofMillis(5009))    .build();    HttpResponse<String> response =    client.send(request, HttpResponse.BodyHandlers.ofString());    System.out.println(response.statusCode());  System.out.println(response.body()); }

1. authenticator可以用來設置HTTP authentication，比如Basic authentication
2. 雖然Basic authentication也可以自己設置header，不過通過authenticator省得自己去構造header

設置header

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@Test public void testCookies() throws IOException, InterruptedException {  HttpClient client = HttpClient.newBuilder()    .connectTimeout(Duration.ofMillis(5000))    .build();  HttpRequest request = HttpRequest.newBuilder()    .uri(URI.create("http://localhost:8080/json/cookie"))    .header("Cookie","JSESSIONID=4f994730-32d7-4e22-a18b-25667ddeb636; userId=java11")    .timeout(Duration.ofMillis(5009))    .build();  HttpResponse<String> response =    client.send(request, HttpResponse.BodyHandlers.ofString());    System.out.println(response.statusCode());  System.out.println(response.body()); }

通過request可以自己設置header，多個header可直接傳入可變參數headers（String數組），或者傳入傳統的Map型的header直接流轉換爲headers

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@Test public void testRequestWithHeaders(Map<String,String> headers) throws IOException, InterruptedException {  HttpClient client = HttpClient.newBuilder()    .connectTimeout(Duration.ofMillis(5000))    .build();  HttpRequest request = HttpRequest.newBuilder()    .uri(URI.create("http://localhost:8080/json/cookie"))    .headers(headers.entrySet().stream().flatMap(e->Stream.of(e.getKey(),e.getValue())).collect(Collectors.toList()).stream().toArray(String[]::new))    .timeout(Duration.ofMillis(5009))    .build();  HttpResponse<String> response =    client.send(request, HttpResponse.BodyHandlers.ofString());    System.out.println(response.statusCode());  System.out.println(response.body()); }

 

 

 

GET

同步

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@Test public void testSyncGet() throws IOException, InterruptedException {  HttpClient client = HttpClient.newHttpClient();  HttpRequest request = HttpRequest.newBuilder()    .uri(URI.create("https://www.baidu.com"))    .build();    HttpResponse<String> response =    client.send(request, HttpResponse.BodyHandlers.ofString());    System.out.println(response.body()); }

異步

 

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@Test public void testAsyncGet() throws ExecutionException, InterruptedException {  HttpClient client = HttpClient.newHttpClient();  HttpRequest request = HttpRequest.newBuilder()    .uri(URI.create("https://www.baidu.com"))    .build();    CompletableFuture<String> result = client.sendAsync(request, HttpResponse.BodyHandlers.ofString())    .thenApply(HttpResponse::body);  System.out.println(result.get()); }

POST表單

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@Test public void testPostForm() throws IOException, InterruptedException {  HttpClient client = HttpClient.newBuilder().build();  HttpRequest request = HttpRequest.newBuilder()    .uri(URI.create("http://www.w3school.com.cn/demo/demo_form.asp"))    .header("Content-Type","application/x-www-form-urlencoded")    .POST(HttpRequest.BodyPublishers.ofString("name1=value1&name2=value2"))    .build();    HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());  System.out.println(response.statusCode()); }

header指定內容是表單類型，然後通過BodyPublishers.ofString傳遞表單數據，需要自己構建表單參數

POST JSON

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@Test public void testPostJsonGetJson() throws ExecutionException, InterruptedException, JsonProcessingException {  ObjectMapper objectMapper = new ObjectMapper();  StockDto dto = new StockDto();  dto.setName("hj");  dto.setSymbol("hj");  dto.setType(StockDto.StockType.SH);  String requestBody = objectMapper    .writerWithDefaultPrettyPrinter()    .writeValueAsString(dto);    HttpRequest request = HttpRequest.newBuilder(URI.create("http://localhost:8080/json/demo"))    .header("Content-Type", "application/json")    .POST(HttpRequest.BodyPublishers.ofString(requestBody))    .build();    CompletableFuture<StockDto> result = HttpClient.newHttpClient()    .sendAsync(request, HttpResponse.BodyHandlers.ofString())    .thenApply(HttpResponse::body)    .thenApply(body -> {     try {      return objectMapper.readValue(body,StockDto.class);     } catch (IOException e) {      return new StockDto();     }    });  System.out.println(result.get()); }

post json的話，body自己json化爲string，然後header指定是json格式

文件上傳

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@Test public void testUploadFile() throws IOException, InterruptedException, URISyntaxException {  HttpClient client = HttpClient.newHttpClient();  Path path = Path.of(getClass().getClassLoader().getResource("body.txt").toURI());  File file = path.toFile();    String multipartFormDataBoundary = "Java11HttpClientFormBoundary";  org.apache.http.HttpEntity multipartEntity = MultipartEntityBuilder.create()    .addPart("file", new FileBody(file, ContentType.DEFAULT_BINARY))    .setBoundary(multipartFormDataBoundary) //要設置，否則阻塞    .build();    HttpRequest request = HttpRequest.newBuilder()    .uri(URI.create("http://localhost:8080/file/upload"))    .header("Content-Type", "multipart/form-data; boundary=" + multipartFormDataBoundary)    .POST(HttpRequest.BodyPublishers.ofInputStream(() -> {     try {      return multipartEntity.getContent();     } catch (IOException e) {      e.printStackTrace();      throw new RuntimeException(e);     }    }))    .build();    HttpResponse<String> response =    client.send(request, HttpResponse.BodyHandlers.ofString());    System.out.println(response.body()); }

1. 官方的HttpClient並沒有提供類似WebClient那種現成的BodyInserters.fromMultipartData方法，因此這裏需要自己轉換
2. 這裏使用org.apache.httpcomponents(httpclient及httpmime)的MultipartEntityBuilder構建multipartEntity，最後通過HttpRequest.BodyPublishers.ofInputStream來傳遞內容
3. 這裏header要指定Content-Type值爲multipart/form-data以及boundary的值，否則服務端可能無法解析

文件下載

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@Test public void testAsyncDownload() throws ExecutionException, InterruptedException {  HttpClient client = HttpClient.newHttpClient();  HttpRequest request = HttpRequest.newBuilder()    .uri(URI.create("http://localhost:8080/file/download"))    .build();    CompletableFuture<Path> result = client.sendAsync(request, HttpResponse.BodyHandlers.ofFile(Paths.get("/tmp/body.txt")))    .thenApply(HttpResponse::body);  System.out.println(result.get()); }

使用HttpResponse.BodyHandlers.ofFile來接收文件

併發請求

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@Test public void testConcurrentRequests(){  HttpClient client = HttpClient.newHttpClient();  List<String> urls = List.of("http://www.baidu.com","http://www.alibaba.com/","http://www.tencent.com");  List<HttpRequest> requests = urls.stream()    .map(url -> HttpRequest.newBuilder(URI.create(url)))    .map(reqBuilder -> reqBuilder.build())    .collect(Collectors.toList());    List<CompletableFuture<HttpResponse<String>>> futures = requests.stream()    .map(request -> client.sendAsync(request, HttpResponse.BodyHandlers.ofString()))    .collect(Collectors.toList());  futures.stream()    .forEach(e -> e.whenComplete((resp,err) -> {     if(err != null){      err.printStackTrace();     }else{      System.out.println(resp.body());      System.out.println(resp.statusCode());     }    }));  CompletableFuture.allOf(futures    .toArray(CompletableFuture<?>[]::new))    .join(); }

• sendAsync方法返回的是CompletableFuture，可以方便地進行轉換、組合等操作
• 這裏使用CompletableFuture.allOf組合在一起，最後調用join等待所有future完成

錯誤處理

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@Test  public void testHandleException() throws ExecutionException, InterruptedException {   HttpClient client = HttpClient.newBuilder()     .connectTimeout(Duration.ofMillis(5000))     .build();   HttpRequest request = HttpRequest.newBuilder()     .uri(URI.create("https://twitter.com"))     .build();     CompletableFuture<String> result = client.sendAsync(request, HttpResponse.BodyHandlers.ofString()) //    .whenComplete((resp,err) -> { //     if(err != null){ //      err.printStackTrace(); //     }else{ //      System.out.println(resp.body()); //      System.out.println(resp.statusCode()); //     } //    })     .thenApply(HttpResponse::body)     .exceptionally(err -> {      err.printStackTrace();      return "fallback";     });   System.out.println(result.get());  }

• HttpClient異步請求返回的是CompletableFuture<HttpResponse<T>>，其自帶exceptionally方法可以用來做fallback處理
• 另外值得注意的是HttpClient不像WebClient那樣，它沒有對4xx或5xx的狀態碼拋出異常，需要自己根據情況來處理，手動檢測狀態碼拋出異常或者返回其他內容

HTTP2

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@Test public void testHttp2() throws URISyntaxException {  HttpClient.newBuilder()    .followRedirects(HttpClient.Redirect.NEVER)    .version(HttpClient.Version.HTTP_2)    .build()    .sendAsync(HttpRequest.newBuilder()        .uri(new URI("https://http2.akamai.com/demo"))        .GET()        .build(),      HttpResponse.BodyHandlers.ofString())    .whenComplete((resp,t) -> {     if(t != null){      t.printStackTrace();     }else{      System.out.println(resp.version());      System.out.println(resp.statusCode());     }    }).join(); }

執行之後可以看到返回的response的version爲HTTP_2

WebSocket

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@Test public void testWebSocket() throws InterruptedException {  HttpClient client = HttpClient.newHttpClient();  WebSocket webSocket = client.newWebSocketBuilder()    .buildAsync(URI.create("ws://localhost:8080/echo"), new WebSocket.Listener() {       @Override     public CompletionStage<?> onText(WebSocket webSocket, CharSequence data, boolean last) {      // request one more      webSocket.request(1);        // Print the message when it's available      return CompletableFuture.completedFuture(data)        .thenAccept(System.out::println);     }    }).join();  webSocket.sendText("hello ", false);  webSocket.sendText("world ",true);    TimeUnit.SECONDS.sleep(10);  webSocket.sendClose(WebSocket.NORMAL_CLOSURE, "ok").join(); }

• HttpClient支持HTTP2，也包含了WebSocket，通過newWebSocketBuilder去構造WebSocket
• 傳入listener進行接收消息，要發消息的話，使用WebSocket來發送，關閉使用sendClose方法

reactive streams

HttpClient本身就是reactive的，支持reactive streams，這裏舉ResponseSubscribers.ByteArraySubscriber的源碼看看：
java.net.http/jdk/internal/net/http/ResponseSubscribers.java

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public static class ByteArraySubscriber<T> implements BodySubscriber<T> {   private final Function<byte[], T> finisher;   private final CompletableFuture<T> result = new MinimalFuture<>();   private final List<ByteBuffer> received = new ArrayList<>();     private volatile Flow.Subscription subscription;     public ByteArraySubscriber(Function<byte[],T> finisher) {    this.finisher = finisher;   }     @Override   public void onSubscribe(Flow.Subscription subscription) {    if (this.subscription != null) {     subscription.cancel();     return;    }    this.subscription = subscription;    // We can handle whatever you've got    subscription.request(Long.MAX_VALUE);   }     @Override   public void onNext(List<ByteBuffer> items) {    // incoming buffers are allocated by http client internally,    // and won't be used anywhere except this place.    // So it's free simply to store them for further processing.    assert Utils.hasRemaining(items);    received.addAll(items);   }     @Override   public void onError(Throwable throwable) {    received.clear();    result.completeExceptionally(throwable);   }     static private byte[] join(List<ByteBuffer> bytes) {    int size = Utils.remaining(bytes, Integer.MAX_VALUE);    byte[] res = new byte[size];    int from = 0;    for (ByteBuffer b : bytes) {     int l = b.remaining();     b.get(res, from, l);     from += l;    }    return res;   }     @Override   public void onComplete() {    try {     result.complete(finisher.apply(join(received)));     received.clear();    } catch (IllegalArgumentException e) {     result.completeExceptionally(e);    }   }     @Override   public CompletionStage<T> getBody() {    return result;   }  }

1. BodySubscriber接口繼承了Flow.Subscriber<List<ByteBuffer>>接口
2. 這裏的Subscription來自Flow類，該類是java9引入的，裏頭包含了支持Reactive Streams的實現

小結

HttpClient在Java11從incubator變爲正式版，相對於傳統的HttpUrlConnection其提升可不是一點半點，不僅支持異步，也支持reactive streams，同時也支持了HTTP2以及WebSocket，非常值得大家使用。