Java11新特性之HttpClient小试牛刀-eolink官网

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

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

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 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 response =

client.send(request, HttpResponse.BodyHandlers.ofString());

System.out.println(response.statusCode());

System.out.println(response.body());

}

authenticator可以用来设置HTTP authentication，比如Basic authentication

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(UDhEwHQYORI.create("http://localhost:8080/json/cookie"))

.header("Cookie","JSESSIONID=4f994730-32d7-4e22-a18b-25667ddeb636; userId=java11")

.timeout(Duration.ofMillis(5009))

.build();

HttpResponse 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://baidu.com"))

.build();

HttpResponse 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://baidu.com"))

.build();

CompletableFuture 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://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 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 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 multipartFormhttp://DataBoundary = "Java11HttpClientFormBoundary";

org.apache.http.HttpEntity multipartEntity = MultipartEntityBuilder.create()

.addPart("file", new FileBody(file, ContentType.DEFAULT_BINARY))

.setBoundary(multipartDhEwHQYOFormDataBoundary) //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 response =

client.send(request, HttpResponse.BodyHandlers.ofString());

System.out.println(response.body());

}

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

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

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 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 urls = List.of("http://baidu.com","http://alibaba.com/","http://tencent.com");

List requests = urls.stream()

.map(url -> HttpRequest.newBuilder(URI.create(url)))

.map(reqBuilder -> reqBuilder.build())

.collect(Collectors.toList());

List>> 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 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>，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 implements BodySubscriber {

private final Function finisher;

private final CompletableFuture result = new MinimalFuture<>();

private final List received = new ArrayList<>();

private volatile Flow.Subscription subscription;

public ByteArraySubscriber(Function 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 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 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 getBody() {

return result;

}

BodySubscriber接口继承了Flow.Subscriber>接口

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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