Java11新特性之HttpClient小试牛刀

序

本文主要研究一下Java11的HttpClient的基本使用。

变化

1. 从java9的jdk.incubator.httpclient模块迁移到java.net.http模块，包名由jdk.incubator.http改为java.net.http
2. 原来的诸如HttpResponse.BodyHandler.asString()方法变更为HttpResponse.BodyHandlers.ofString()，变化一为BodyHandler改为BodyHandlers，变化二为asXXX()之类的方法改为ofXXX()，由as改为of

实例

设置超时时间

 @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实例

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实例

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)

设置authenticator

 @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可以用来设置HTTP authentication，比如Basic authentication
2. 虽然Basic authentication也可以自己设置header，不过通过authenticator省得自己去构造header

设置header

 @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());
 }

通过request可以自己设置header

GET

同步

 @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());
 }

异步

 @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表单

 @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指定内容是表单类型，然后通过BodyPublishers.ofString传递表单数据，需要自己构建表单参数

POST JSON

 @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的话，body自己json化为string，然后header指定是json格式

文件上传

 @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) //要设置，否则阻塞
    .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并没有提供类似WebClient那种现成的BodyInserters.fromMultipartData方法，因此这里需要自己转换
2. 这里使用org.apache.httpcomponents(httpclient及httpmime)的MultipartEntityBuilder构建multipartEntity，最后通过HttpRequest.BodyPublishers.ofInputStream来传递内容
3. 这里header要指定Content-Type值为multipart/form-data以及boundary的值，否则服务端可能无法解析

文件下载

 @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来接收文件

并发请求

 @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，可以方便地进行转换、组合等操作
• 这里使用CompletableFuture.allOf组合在一起，最后调用join等待所有future完成

错误处理

 @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异步请求返回的是CompletableFuture<HttpResponse<T>>，其自带exceptionally方法可以用来做fallback处理
• 另外值得注意的是HttpClient不像WebClient那样，它没有对4xx或5xx的状态码抛出异常，需要自己根据情况来处理，手动检测状态码抛出异常或者返回其他内容

HTTP2

 @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();
 }

执行之后可以看到返回的response的version为HTTP_2

WebSocket

 @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，通过newWebSocketBuilder去构造WebSocket
• 传入listener进行接收消息，要发消息的话，使用WebSocket来发送，关闭使用sendClose方法

reactive streams

HttpClient本身就是reactive的，支持reactive streams，这里举ResponseSubscribers.ByteArraySubscriber的源码看看：
java.net.http/jdk/internal/net/http/ResponseSubscribers.java

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接口继承了Flow.Subscriber<List<ByteBuffer>>接口
2. 这里的Subscription来自Flow类，该类是java9引入的，里头包含了支持Reactive Streams的实现

小结

HttpClient在Java11从incubator变为正式版，相对于传统的HttpUrlConnection其提升可不是一点半点，不仅支持异步，也支持reactive streams，同时也支持了HTTP2以及WebSocket，非常值得大家使用。

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