Java 11 HTTP Client库的使用

前言

每种编程语言里最常用的库恐怕是Http请求库了，如python里的requests包，nodejs里的request模块。
在Java世界里，也是百花齐放，山头林立。常用的有：

• HttpURLConnection: 最早的JDK提供的类
• Java 11提供的HttpClient
• Apache HttpComponents项目中的HTTPClient
• Square提供的OkHttpClient
• Spring 自带的WebClient

本文着重介绍JDK 11的HttpClient。

Apache HttpComponents

该组件提供了两个核心类：

• HttpCore: 更底层的传输处理类
• HttpClient：基于HttpCore实现的HTTP-compliant 处理类

JDK 11 HTTP Client使用举例

JDK 11开始新增了HttpClient这个组件，方便我们发送同步或异步的http请求。

Post同步的json数据

public void invokePost() {
  
  try {
   String requestBody = prepareRequest();
   HttpClient client = HttpClient.newHttpClient();
   HttpRequest request = HttpRequest
     .newBuilder()
     .uri(URI.create("https://reqbin.com/echo/post/json"))
     .POST(HttpRequest.BodyPublishers.ofString(requestBody))
     .header("Accept", "application/json")
     .build();

   HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());

   System.out.println(response.body());
  } catch (IOException | InterruptedException e) {
   e.printStackTrace();
  }
 }

 private String prepareRequest() throws JsonProcessingException {
  var values = new HashMap<String, String>() {
   {
    put("Id", "12345");
    put("Customer", "Roger Moose");
    put("Quantity", "3");
    put("Price","167.35");
   }
  };

  var objectMapper = new ObjectMapper();
  String requestBody = objectMapper.writeValueAsString(values);
  return requestBody;
 }

发送异步请求

用于同时发送大量的Http请求的场景，例如爬虫：

public void invoke() throws URISyntaxException {
  
  HttpClient client = HttpClient.newBuilder()
      .version(Version.HTTP_2)
      .followRedirects(Redirect.NORMAL)
      .build();
  
  HttpRequest request = HttpRequest.newBuilder()
     .uri(new URI(URLConstants.URL))
     .GET()
     .header(URLConstants.API_KEY_NAME, URLConstants.API_KEY_VALUE)
     .timeout(Duration.ofSeconds(10))
     .build();
  
  
  client.sendAsync(request, BodyHandlers.ofString())
    .thenApply(HttpResponse::body)
    .thenAccept(System.out::println)
    .join();
 }

会话保持

//使用默认的CookieManager，并且接受所有第三方Cookie
cookieManager = new CookieManager();
cookieManager.setCookiePolicy(CookiePolicy.ACCEPT_ALL);
httpClient = HttpClient.newBuilder()
        .connectTimeout(Duration.ofMillis(5000))
        .cookieHandler(cookieManager)//注意在此步骤送送入
        .followRedirects(HttpClient.Redirect.NORMAL)
        .build();

爬虫示例：HttpClient 并发编程

HttpClient uses executor java.util.concurrent.Executors.newCachedThreadPool().

private static final ExecutorService executorService = Executors.newFixedThreadPool(5);

private static final HttpClient httpClient = HttpClient.newBuilder()
            .executor(executorService)
            .version(HttpClient.Version.HTTP_2)
            .connectTimeout(Duration.ofSeconds(10))
            .build();

    public static void main(String[] args) throws Exception {

        List<URI> targets = Arrays.asList(
                new URI("https://httpbin.org/get?name=mkyong1"),
                new URI("https://httpbin.org/get?name=mkyong2"),
                new URI("https://httpbin.org/get?name=mkyong3"));

        List<CompletableFuture<String>> result = targets.stream()
                .map(url -> httpClient.sendAsync(
                        HttpRequest.newBuilder(url)
                                .GET()
                                .setHeader("User-Agent", "Java 11 HttpClient Bot")
                                .build(),
                        HttpResponse.BodyHandlers.ofString())
                        .thenApply(response -> response.body()))
                .collect(Collectors.toList());

        for (CompletableFuture<String> future : result) {
            System.out.println(future.get());
        }

    }

发送multipart/form-data数据

遗憾的是，JDK 11 HttpClient对这类数据支持不太友好。

private val httpClient: HttpClient = HttpClient.newHttpClient()

fun main() {
    val file = File(
        LocalTest::class.java.classLoader.getResource("my_pic_from_resources.jpg").file
    )
    val token = "123456:ABC-DEF1234ghIkl-zyx57W2v1u123ew11"

    val data: MutableMap<String, Any> = LinkedHashMap()
    data["chat_id"] = "123456789"
    data["photo"] = file
    val boundary: String = BigInteger(35, Random()).toString()

    val request = HttpRequest.newBuilder()
        .uri(URI.create("https://api.telegram.org/bot$token/sendPhoto"))
        .postMultipartFormData(boundary, data)
        .build()

    val response = httpClient.send(request, HttpResponse.BodyHandlers.ofString())
    println(response)
}

fun HttpRequest.Builder.postMultipartFormData(boundary: String, data: Map<String, Any>): HttpRequest.Builder {
    val byteArrays = ArrayList<ByteArray>()
    val separator = "--$boundary\r\nContent-Disposition: form-data; name=".toByteArray(StandardCharsets.UTF_8)

    for (entry in data.entries) {
        byteArrays.add(separator)
        when(entry.value) {
            is File -> {
                val file = entry.value as File
                val path = Path.of(file.toURI())
                val mimeType = Files.probeContentType(path)
                byteArrays.add("\"${entry.key}\"; filename=\"${path.fileName}\"\r\nContent-Type: $mimeType\r\n\r\n".toByteArray(StandardCharsets.UTF_8))
                byteArrays.add(Files.readAllBytes(path))
                byteArrays.add("\r\n".toByteArray(StandardCharsets.UTF_8))
            }
            else -> byteArrays.add("\"${entry.key}\"\r\n\r\n${entry.value}\r\n".toByteArray(StandardCharsets.UTF_8))
        }
    }
    byteArrays.add("--$boundary--".toByteArray(StandardCharsets.UTF_8))

    this.header("Content-Type", "multipart/form-data;boundary=$boundary")
        .POST(HttpRequest.BodyPublishers.ofByteArrays(byteArrays))
    return this
}

或者，借用Apache Http组件的部分类：

import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpRequest.BodyPublishers;
import java.net.http.HttpResponse;
import java.net.http.HttpResponse.BodyHandlers;
import java.nio.channels.Channels;
import java.nio.channels.Pipe;
import java.nio.charset.StandardCharsets;

import org.apache.http.HttpEntity;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.mime.MultipartEntityBuilder;
import org.apache.http.entity.mime.content.StringBody;

public class MultipartRequest {

    public static void main(String[] args) throws Exception {

        /**
        * Create a Multipart request body with MultipartEntityBuilder.
        */
        HttpEntity httpEntity = MultipartEntityBuilder.create()
                // FORM
                .addPart("name",
                        new StringBody("<Spring Cloud>",
                                ContentType.create("application/x-www-form-urlencoded", StandardCharsets.UTF_8)))
                // JSON
                .addPart("info",
                        new StringBody("{\"site\": \"https://www.springcloud.io\"}", ContentType.APPLICATION_JSON))
                // FILE
                .addBinaryBody("logo", new File("C:\\Users\\KevinBlandy\\Desktop\\logo.png"), ContentType.IMAGE_PNG,
                        "logo.png")
                .build();

        /**
        * Use pipeline streams to write the encoded data directly to the network
        * instead of caching it in memory. Because Multipart request bodies contain
        * files, they can cause memory overflows if cached in memory.
        */
        Pipe pipe = Pipe.open();

        // Pipeline streams must be used in a multi-threaded environment. Using one
        // thread for simultaneous reads and writes can lead to deadlocks.
        new Thread(() -> {
            try (OutputStream outputStream = Channels.newOutputStream(pipe.sink())) {
                // Write the encoded data to the pipeline.
                httpEntity.writeTo(outputStream);
            } catch (IOException e) {
                e.printStackTrace();
            }

        }).start();

        HttpClient httpClient = HttpClient.newHttpClient();

        HttpRequest request = HttpRequest.newBuilder(new URI("http://localhost/upload"))
                // The Content-Type header is important, don't forget to set it.
                .header("Content-Type", httpEntity.getContentType().getValue())
                // Reads data from a pipeline stream.
                .POST(BodyPublishers.ofInputStream(() -> Channels.newInputStream(pipe.source()))).build();

        HttpResponse<String> responseBody = httpClient.send(request, BodyHandlers.ofString(StandardCharsets.UTF_8));

        System.out.println(responseBody.body());
    }
}

如果不想引入上面的Apache Http组件，则自己写一个类MultipartFormDataBodyPublisher也行。然后如下使用：

var body = new MultipartFormData()
            .add(StringPart("name", "Hello,")
            .add(StringPart("value", "World!")
            .addFile("f", Path.of("index.html"), "text/html")
            .addFile("cpuinfo", Path.of("/proc/cpuinfo"), "text/html");

var client = HttpClient.newHttpClient();
var request = HttpRequest.newBuilder(URI.create("http://localhost:8080/"))
    .header("Content-Type", body.contentType())
    .POST(body)
    .build();
var response = client.send(request, BodyHandlers.ofLines());
response.body().forEach(line -> System.out.println(line));

其它HTTP Client包装库

methanol

A Lightweight HTTP extensions for Java

cVurl

cVurl is an open-source wrapper for the Java HTTP client. It is written in Java 11 and can be used with any JDK 11.0.2 or newer.

public void cVurl() {
    CVurl cVurl = new CVurl();

    //POST
    Result result = cVurl.post("https://api.imgflip.com/caption_image")
        .queryParams(Map.of(
                "template_id", "112126428",
        "username", "test-user",
        "password", "123test321",
        "text0", "text0",
        "text1", "text1"
        ))
        .asObject(Result.class);

    System.out.println("CVurl POST: " + result);
}

它支持Compression、Multipart、Form data这些Java 11 HttpClient不具备的特性。

Avaje-HTTP

• Fluid API for building URLs and payload
• JSON marshaling using Avaje Jsonb/Jackson/Gson
• Light Feign-style interfaces via annotation processing.
• Request/Response Interception
• Authorization via Basic Auth or OAuth Bearer Tokens
• Async and sync API

个人建议

在实际项目中，设计符合自身项目需求的HTTP client接口，并基于JDK 11 HTTP client实现，独立于任何上述库。文章来源地址https://www.toymoban.com/news/detail-706802.html

参考链接

• comparison-of-java-http-clients
• A closer look at the Java 11 HTTP Client
• cvurl
• methanol
• avaje-http
• java.net.HttpClient multipart/form-data BodyPublisher

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