Apache HttpClient 5 使用详细教程

未读代码

发布于 2022-11-21 21:31:25

5.8K0

发布于 2022-11-21 21:31:25

文章被收录于专栏：程序猿阿朗的专栏

HTTP Components Logo

超文本传输协议（HTTP）可能是当今互联网上最重要的协议之一，Web 服务、微服务以及支持网络的各种设备上的服务几乎都是 HTTP 协议，HTTP 协议已经从 Web 浏览器走向了更广泛的使用场景。

虽然 java.net 包已经提供了 HTTP 访问资源的基本功能，但是它不够灵活，而且不能随心所欲的进行自定义。Apache HttpClient 5 是一个开源的 HTTP 工具包，可以支持最新 HTTP 协议标准，且有丰富的 API 和强大的扩展特性，可以用于构建任何需要进行 HTTP 协议处理的应用程序。

这篇文章介绍 Apache HttpClient 5 中最为常见的一些用法，通过这篇文章可以快速的入门使用 HttpClient 5，主要内容包括 HttpClient 5 的 Get 请求、Post 请求、如何携带参数、JSON 参数、设置超时、异步请求、操作 Cookie、表单登录、基本认证、Digest 认证以及自定义 HTTP 请求拦截器等。

HttpClient 5 依赖

HttpClient 5 Maven 依赖

<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents.client5/httpclient5 -->
<dependency>
    <groupId>org.apache.httpcomponents.client5</groupId>
    <artifactId>httpclient5</artifactId>
    <version>5.1.3</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents.client5/httpclient5-fluent -->
<dependency>
    <groupId>org.apache.httpcomponents.client5</groupId>
    <artifactId>httpclient5-fluent</artifactId>
    <version>5.1.3</version>
</dependency>

HttpClient 5 Gradle 依赖

implementation 'org.apache.httpcomponents.client5:httpclient5:5.1.3'
implementation 'org.apache.httpcomponents.client5:httpclient5-fluent:5.1.3'

HttpClient 5 GET 请求

package com.wdbyte.httpclient;

import java.io.IOException;

import org.apache.hc.client5.http.classic.methods.HttpGet;
import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;
import org.apache.hc.client5.http.impl.classic.CloseableHttpResponse;
import org.apache.hc.client5.http.impl.classic.HttpClients;
import org.apache.hc.core5.http.HttpEntity;
import org.apache.hc.core5.http.ParseException;
import org.apache.hc.core5.http.io.entity.EntityUtils;

/**
 * @author https://www.wdbyte.com
 */
public class HttpClient5Get {

    public static void main(String[] args) {
        String result = get("http://httpbin.org/get");
        System.out.println(result);
    }

    public static String get(String url) {
        String resultContent = null;
        HttpGet httpGet = new HttpGet(url);
        try (CloseableHttpClient httpclient = HttpClients.createDefault()) {
            try (CloseableHttpResponse response = httpclient.execute(httpGet)) {
                // 获取状态码
                System.out.println(response.getVersion()); // HTTP/1.1
                System.out.println(response.getCode()); // 200
                System.out.println(response.getReasonPhrase()); // OK
                HttpEntity entity = response.getEntity();
                // 获取响应信息
                resultContent = EntityUtils.toString(entity);
            }
        } catch (IOException | ParseException e) {
            e.printStackTrace();
        }
        return resultContent;
    }

}

响应信息：

HTTP/1.1
200
OK
{
  "args": {}, 
  "headers": {
    "Accept-Encoding": "gzip, x-gzip, deflate", 
    "Host": "httpbin.org", 
    "User-Agent": "Apache-HttpClient/5.1.3 (Java/17)", 
    "X-Amzn-Trace-Id": "Root=1-62bb1891-5ab5e5376ed960471bf32f17"
  }, 
  "origin": "47.251.4.198", 
  "url": "http://httpbin.org/get"
}

HttpClient 5 Fluent GET

使用 Apache HttpClient 5 提供的 Fluent API 可以更便捷的发起 GET 请求，但是可操作的地方较少。

依赖：

<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents.client5/httpclient5-fluent -->
<dependency>
    <groupId>org.apache.httpcomponents.client5</groupId>
    <artifactId>httpclient5-fluent</artifactId>
    <version>5.1.3</version>
</dependency>

示例：

package com.wdbyte.httpclient;

import java.io.IOException;

import org.apache.hc.client5.http.fluent.Request;
import org.apache.hc.client5.http.fluent.Response;

/**
* @author https://www.wdbyte.com
 */
public class HttpClient5GetFluent {

    public static void main(String[] args) {
        System.out.println(get("http://httpbin.org/get"));
    }

    public static String get(String url) {
        String result = null;
        try {
            Response response = Request.get(url).execute();
            result = response.returnContent().asString();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return result;
    }

}

输出信息：

{
  "args": {}, 
  "headers": {
    "Accept-Encoding": "gzip, x-gzip, deflate", 
    "Host": "httpbin.org", 
    "User-Agent": "Apache-HttpClient/5.1.3 (Java/17)", 
    "X-Amzn-Trace-Id": "Root=1-62bb190e-1ba46a92645843a04c55da32"
  }, 
  "origin": "47.251.4.198", 
  "url": "http://httpbin.org/get"
}

HttpClient5 GET 请求参数

使用 URIBuilder 的 addParameters() 方法来构建 GET 请求的参数。

package com.wdbyte.httpclient;

import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.ArrayList;
import java.util.List;

import org.apache.hc.client5.http.classic.methods.HttpGet;
import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;
import org.apache.hc.client5.http.impl.classic.CloseableHttpResponse;
import org.apache.hc.client5.http.impl.classic.HttpClients;
import org.apache.hc.core5.http.HttpEntity;
import org.apache.hc.core5.http.NameValuePair;
import org.apache.hc.core5.http.ParseException;
import org.apache.hc.core5.http.io.entity.EntityUtils;
import org.apache.hc.core5.http.message.BasicNameValuePair;
import org.apache.hc.core5.net.URIBuilder;

/**
* @author https://www.wdbyte.com
 */
public class HttpClient5GetParams {

    public static void main(String[] args) {
        String result = get("http://httpbin.org/get");
        System.out.println(result);
    }

    public static String get(String url) {
        String resultContent = null;
        HttpGet httpGet = new HttpGet(url);
        // 表单参数
        List<NameValuePair> nvps = new ArrayList<>();
        // GET 请求参数
        nvps.add(new BasicNameValuePair("username", "wdbyte.com"));
        nvps.add(new BasicNameValuePair("password", "secret"));
        // 增加到请求 URL 中
        try {
            URI uri = new URIBuilder(new URI(url))
                .addParameters(nvps)
                .build();
            httpGet.setUri(uri);
        } catch (URISyntaxException e) {
            throw new RuntimeException(e);
        }

        try (CloseableHttpClient httpclient = HttpClients.createDefault()) {
            try (CloseableHttpResponse response = httpclient.execute(httpGet)) {
                // 获取状态码
                System.out.println(response.getVersion()); // HTTP/1.1
                System.out.println(response.getCode()); // 200
                System.out.println(response.getReasonPhrase()); // OK
                HttpEntity entity = response.getEntity();
                // 获取响应信息
                resultContent = EntityUtils.toString(entity);
            }
        } catch (IOException | ParseException e) {
            e.printStackTrace();
        }
        return resultContent;
    }
}

输出信息：

{
  "args": {
    "password": "secret", 
    "username": "wdbyte.com"
  }, 
  "headers": {
    "Accept-Encoding": "gzip, x-gzip, deflate", 
    "Host": "httpbin.org", 
    "User-Agent": "Apache-HttpClient/5.1.3 (Java/1.8.0_151)", 
    "X-Amzn-Trace-Id": "Root=1-62ecc660-69d58a226aefb1b6226541ec"
  }, 
  "origin": "42.120.75.185", 
  "url": "http://httpbin.org/get?username=wdbyte.com&password=secret"
}

下面是通过抓包得到的请求响应信息格式：

// 请求信息
GET /get?username=wdbyte.com&password=secret HTTP/1.1
Accept-Encoding: gzip, x-gzip, deflate
Host: httpbin.org
Connection: keep-alive
User-Agent: Apache-HttpClient/5.1.3 (Java/1.8.0_151)

// 响应信息
HTTP/1.1 200 OK
Date: Fri, 05 Aug 2022 07:27:30 GMT
Content-Type: application/json
Content-Length: 405
Connection: keep-alive
Server: gunicorn/19.9.0
Access-Control-Allow-Origin: *
Access-Control-Allow-Credentials: true

{
  "args": {
    "password": "secret", 
    "username": "wdbyte.com"
  }, 
  "headers": {
    "Accept-Encoding": "gzip, x-gzip, deflate", 
    "Host": "httpbin.org", 
    "User-Agent": "Apache-HttpClient/5.1.3 (Java/1.8.0_151)", 
    "X-Amzn-Trace-Id": "Root=1-62ecc660-69d58a226aefb1b6226541ec"
  }, 
  "origin": "42.120.75.185", 
  "url": "http://httpbin.org/get?username=wdbyte.com&password=secret"
}

HttpClient 5 POST 请求

下面演示发起一个 POST 请求，并携带表单参数。

参数：username=wdbyte.com&password=secret

package com.wdbyte.httpclient;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.apache.hc.client5.http.classic.methods.HttpPost;
import org.apache.hc.client5.http.entity.UrlEncodedFormEntity;
import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;
import org.apache.hc.client5.http.impl.classic.CloseableHttpResponse;
import org.apache.hc.client5.http.impl.classic.HttpClients;
import org.apache.hc.core5.http.HttpEntity;
import org.apache.hc.core5.http.NameValuePair;
import org.apache.hc.core5.http.ParseException;
import org.apache.hc.core5.http.io.entity.EntityUtils;
import org.apache.hc.core5.http.message.BasicNameValuePair;

/**
* @author https://www.wdbyte.com
 */
public class HttpClient5Post {

    public static void main(String[] args) {
        String result = post("http://httpbin.org/post");
        System.out.println(result);
    }
    public static String post(String url) {
        String result = null;
        HttpPost httpPost = new HttpPost(url);
        // 表单参数
        List<NameValuePair> nvps = new ArrayList<>();
        // POST 请求参数
        nvps.add(new BasicNameValuePair("username", "wdbyte.com"));
        nvps.add(new BasicNameValuePair("password", "secret"));
        httpPost.setEntity(new UrlEncodedFormEntity(nvps));
        try (CloseableHttpClient httpclient = HttpClients.createDefault()) {
            try (CloseableHttpResponse response = httpclient.execute(httpPost)) {
                System.out.println(response.getVersion()); // HTTP/1.1
                System.out.println(response.getCode()); // 200
                System.out.println(response.getReasonPhrase()); // OK

                HttpEntity entity = response.getEntity();
                // 获取响应信息
                result = EntityUtils.toString(entity);
                // 确保流被完全消费
                EntityUtils.consume(entity);
            }
        } catch (IOException | ParseException e) {
            e.printStackTrace();
        }
        return result;
    }

}

输出信息：

HTTP/1.1
200
OK
{
  "args": {}, 
  "data": "", 
  "files": {}, 
  "form": {
    "password": "secret", 
    "username": "wdbyte.com"
  }, 
  "headers": {
    "Accept-Encoding": "gzip, x-gzip, deflate", 
    "Content-Length": "35", 
    "Content-Type": "application/x-www-form-urlencoded; charset=ISO-8859-1", 
    "Host": "httpbin.org", 
    "User-Agent": "Apache-HttpClient/5.1.3 (Java/17)", 
    "X-Amzn-Trace-Id": "Root=1-62bb1ac8-489b2100728c81d70797a482"
  }, 
  "json": null, 
  "origin": "183.128.136.89", 
  "url": "http://httpbin.org/post"
}

下面是通过 Wireshark 抓包得到的请求信息：

POST /post HTTP/1.1
Accept-Encoding: gzip, x-gzip, deflate
Content-Length: 35
Content-Type: application/x-www-form-urlencoded; charset=ISO-8859-1
Host: httpbin.org
Connection: keep-alive
User-Agent: Apache-HttpClient/5.1.3 (Java/17)

username=wdbyte.com&password=secret

HttpClient 5 Fluent POST

使用 Apache HttpClient 5 提供的 Fluent API 可以更便捷的发起 POST 请求，但是可操作的地方较少。

一样发送一个简单的表单参数：username=wdbyte.com&password=secret

package com.wdbyte.httpclient;

import java.io.IOException;

import org.apache.hc.client5.http.fluent.Request;
import org.apache.hc.core5.http.message.BasicNameValuePair;

/**
* @author https://www.wdbyte.com
 */
public class HttpClient5PostFluent {

    public static void main(String[] args) {
        String result = post("http://httpbin.org/post");
        System.out.println(result);
    }

    public static String post(String url) {
        String result = null;
        Request request = Request.post(url);
        // POST 请求参数
        request.bodyForm(
            new BasicNameValuePair("username", "wdbyte.com"),
            new BasicNameValuePair("password", "secret"));
        try {
            result = request.execute().returnContent().asString();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return result;
    }
}

输出信息：

{
  "args": {}, 
  "data": "", 
  "files": {}, 
  "form": {
    "password": "secret", 
    "username": "wdbyte.com"
  }, 
  "headers": {
    "Accept-Encoding": "gzip, x-gzip, deflate", 
    "Content-Length": "35", 
    "Content-Type": "application/x-www-form-urlencoded; charset=ISO-8859-1", 
    "Host": "httpbin.org", 
    "User-Agent": "Apache-HttpClient/5.1.3 (Java/17)", 
    "X-Amzn-Trace-Id": "Root=1-62bb1c8a-7aee8c004f06919f31a2b533"
  }, 
  "json": null, 
  "origin": "183.128.136.89", 
  "url": "http://httpbin.org/post"
}

HttpClient5 POST JSON 参数

使用 StringEntity 类存入 JSON 参数。

package com.wdbyte.httpclient;

import java.io.IOException;

import org.apache.hc.client5.http.classic.methods.HttpPost;
import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;
import org.apache.hc.client5.http.impl.classic.CloseableHttpResponse;
import org.apache.hc.client5.http.impl.classic.HttpClients;
import org.apache.hc.core5.http.ParseException;
import org.apache.hc.core5.http.io.entity.EntityUtils;
import org.apache.hc.core5.http.io.entity.StringEntity;

/**
* @author https://www.wdbyte.com
 */
public class HttpClient5PostWithJson {

    public static void main(String[] args) {
        String json = "{"
            + "    \"password\": \"secret\","
            + "    \"username\": \"wdbyte.com\""
            + "}";
        String result = post("http://httpbin.org/post", json);
        System.out.println(result);
    }

    public static String post(String url, String jsonBody) {
        String result = null;
        HttpPost httpPost = new HttpPost(url);
        httpPost.setEntity(new StringEntity(jsonBody, ContentType.APPLICATION_JSON));
      
        try (CloseableHttpClient httpclient = HttpClients.createDefault()) {
            try (CloseableHttpResponse response = httpclient.execute(httpPost)) {
                // 获取响应信息
                result = EntityUtils.toString(response.getEntity());
            }
        } catch (IOException | ParseException e) {
            e.printStackTrace();
        }
        return result;
    }

}

输出信息：

{
  "args": {}, 
  "data": "{    \"password\": \"secret\",    \"username\": \"wdbyte.com\"}", 
  "files": {}, 
  "form": {}, 
  "headers": {
    "Accept-Encoding": "gzip, x-gzip, deflate", 
    "Content-Length": "55", 
    "Content-Type": "text/plain; charset=ISO-8859-1", 
    "Host": "httpbin.org", 
    "User-Agent": "Apache-HttpClient/5.1.3 (Java/17)", 
    "X-Amzn-Trace-Id": "Root=1-62bb1dbb-5a963c1d798b06be3ee1a15e"
  }, 
  "json": {
    "password": "secret", 
    "username": "wdbyte.com"
  }, 
  "origin": "183.128.136.89", 
  "url": "http://httpbin.org/post"
}

下面是通过 Wireshark 抓包得到的请求响应信息：

// 请求信息
POST /post HTTP/1.1
Accept-Encoding: gzip, x-gzip, deflate
Content-Length: 55
Content-Type: application/json; charset=UTF-8
Host: httpbin.org
Connection: keep-alive
User-Agent: Apache-HttpClient/5.1.3 (Java/17)

{    "password": "secret",    "username": "wdbyte.com"}

// 响应信息
HTTP/1.1 200 OK
Date: Tue, 28 Jun 2022 15:30:17 GMT
Content-Type: application/json
Content-Length: 573
Connection: keep-alive
Server: gunicorn/19.9.0
Access-Control-Allow-Origin: *
Access-Control-Allow-Credentials: true

{
  "args": {}, 
  "data": "{    \"password\": \"secret\",    \"username\": \"wdbyte.com\"}", 
  "files": {}, 
  "form": {}, 
  "headers": {
    "Accept-Encoding": "gzip, x-gzip, deflate", 
    "Content-Length": "55", 
    "Content-Type": "application/json; charset=UTF-8", 
    "Host": "httpbin.org", 
    "User-Agent": "Apache-HttpClient/5.1.3 (Java/17)", 
    "X-Amzn-Trace-Id": "Root=1-62bb1e89-64db55730a0361c720232ccd"
  }, 
  "json": {
    "password": "secret", 
    "username": "wdbyte.com"
  }, 
  "origin": "183.128.136.89", 
  "url": "http://httpbin.org/post"
}

HttpClient 5 设置超时

使用 RequestConfig 对象来配置超时时间。

package com.wdbyte.httpclient;

import java.io.IOException;

import org.apache.hc.client5.http.classic.methods.HttpGet;
import org.apache.hc.client5.http.config.RequestConfig;
import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;
import org.apache.hc.client5.http.impl.classic.CloseableHttpResponse;
import org.apache.hc.client5.http.impl.classic.HttpClients;
import org.apache.hc.core5.http.HttpEntity;
import org.apache.hc.core5.http.ParseException;
import org.apache.hc.core5.http.io.entity.EntityUtils;
import org.apache.hc.core5.util.Timeout;

/**
* @author https://www.wdbyte.com
 */
public class HttpClient5GetWithTimeout {

    public static void main(String[] args) {
        String result = get("http://httpbin.org/get");
        System.out.println(result);
    }

    public static String get(String url) {
        String resultContent = null;
        // 设置超时时间
        RequestConfig config = RequestConfig.custom()
            .setConnectTimeout(Timeout.ofMilliseconds(5000L))
            .setConnectionRequestTimeout(Timeout.ofMilliseconds(5000L))
            .setResponseTimeout(Timeout.ofMilliseconds(5000L))
            .build();
        // 请求级别的超时
        HttpGet httpGet = new HttpGet(url);
        //httpGet.setConfig(config);
        //try (CloseableHttpClient httpclient = HttpClients.createDefault()) {
        // 客户端级别的超时
        try (CloseableHttpClient httpclient = HttpClients.custom().setDefaultRequestConfig(config).build()) {
            try (CloseableHttpResponse response = httpclient.execute(httpGet)) {
                // 获取状态码
                System.out.println(response.getVersion()); // HTTP/1.1
                System.out.println(response.getCode()); // 200
                System.out.println(response.getReasonPhrase()); // OK
                HttpEntity entity = response.getEntity();
                // 获取响应信息
                resultContent = EntityUtils.toString(entity);
            }
        } catch (IOException | ParseException e) {
            e.printStackTrace();
        }
        return resultContent;
    }

}

HttpClient 5 异步请求

下面演示三种 HttpClient 5 异步请求方式。

package com.wdbyte.httpclient;

import java.io.IOException;
import java.nio.CharBuffer;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;

import org.apache.hc.client5.http.async.methods.AbstractCharResponseConsumer;
import org.apache.hc.client5.http.async.methods.SimpleHttpRequest;
import org.apache.hc.client5.http.async.methods.SimpleHttpRequests;
import org.apache.hc.client5.http.async.methods.SimpleHttpResponse;
import org.apache.hc.client5.http.impl.async.CloseableHttpAsyncClient;
import org.apache.hc.client5.http.impl.async.HttpAsyncClients;
import org.apache.hc.core5.concurrent.FutureCallback;
import org.apache.hc.core5.http.ContentType;
import org.apache.hc.core5.http.HttpException;
import org.apache.hc.core5.http.HttpResponse;
import org.apache.hc.core5.http.nio.AsyncRequestProducer;
import org.apache.hc.core5.http.nio.support.AsyncRequestBuilder;

/**
 * HttpClient 5 异步请求
* @author https://www.wdbyte.com
 * @date 2022/06/25
 */
public class HttpClient5Async {

    public static void main(String[] args) {
        getAsync1("http://httpbin.org/get");
        getAsync2("http://httpbin.org/get");
        getAsync3("http://httpbin.org/get");
    }

    /**
     * 异步请求
     *
     * @param url
     * @return
     */
    public static String getAsync1(String url) {
        try (CloseableHttpAsyncClient httpclient = HttpAsyncClients.createDefault()) {
            // 开始 http clinet
            httpclient.start();
            // 执行请求
            SimpleHttpRequest request1 = SimpleHttpRequests.get(url);
            Future<SimpleHttpResponse> future = httpclient.execute(request1, null);
            // 等待直到返回完毕
            SimpleHttpResponse response1 = future.get();
            System.out.println("getAsync1:" + request1.getRequestUri() + "->" + response1.getCode());
        } catch (IOException | ExecutionException | InterruptedException e) {
            throw new RuntimeException(e);
        }
        return null;
    }

    /**
     * 异步请求，根据响应情况回调
     *
     * @param url
     * @return
     */
    public static String getAsync2(String url) {
        try (CloseableHttpAsyncClient httpclient = HttpAsyncClients.createDefault()) {
            // 开始 http clinet
            httpclient.start();
            // 根据请求响应情况进行回调操作
            CountDownLatch latch = new CountDownLatch(1);
            SimpleHttpRequest request = SimpleHttpRequests.get(url);
            httpclient.execute(request, new FutureCallback<SimpleHttpResponse>() {
                @Override
                public void completed(SimpleHttpResponse response2) {
                    latch.countDown();
                    System.out.println("getAsync2:" + request.getRequestUri() + "->" + response2.getCode());
                }

                @Override
                public void failed(Exception ex) {
                    latch.countDown();
                    System.out.println("getAsync2:" + request.getRequestUri() + "->" + ex);
                }

                @Override
                public void cancelled() {
                    latch.countDown();
                    System.out.println("getAsync2:" + request.getRequestUri() + " cancelled");
                }

            });
            latch.await();
        } catch (IOException | InterruptedException e) {
            throw new RuntimeException(e);
        }
        return null;
    }

    /**
     * 异步请求，对响应流做点什么
     *
     * @param url
     * @return
     */
    public static String getAsync3(String url) {
        try (CloseableHttpAsyncClient httpclient = HttpAsyncClients.createDefault()) {
            // 开始 http clinet
            httpclient.start();
            // 根据请求响应情况进行回调操作
            SimpleHttpRequest request = SimpleHttpRequests.get(url);

            CountDownLatch latch = new CountDownLatch(1);
            AsyncRequestProducer producer = AsyncRequestBuilder.get("http://httpbin.org/get").build();
            AbstractCharResponseConsumer<HttpResponse> consumer3 = new AbstractCharResponseConsumer<HttpResponse>() {

                HttpResponse response;

                @Override
                protected void start(HttpResponse response, ContentType contentType) throws HttpException, IOException {
                    System.out.println("getAsync3: 开始响应....");
                    this.response = response;
                }

                @Override
                protected int capacityIncrement() {
                    return Integer.MAX_VALUE;
                }

                @Override
                protected void data(CharBuffer data, boolean endOfStream) throws IOException {
                    System.out.println("getAsync3: 收到数据....");
                    // Do something useful
                }

                @Override
                protected HttpResponse buildResult() throws IOException {
                    System.out.println("getAsync3: 接收完毕...");
                    return response;
                }

                @Override
                public void releaseResources() {
                }

            };
            httpclient.execute(producer, consumer3, new FutureCallback<HttpResponse>() {

                @Override
                public void completed(HttpResponse response) {
                    latch.countDown();
                    System.out.println("getAsync3: "+request.getRequestUri() + "->" + response.getCode());
                }

                @Override
                public void failed(Exception ex) {
                    latch.countDown();
                    System.out.println("getAsync3: "+request.getRequestUri() + "->" + ex);
                }

                @Override
                public void cancelled() {
                    latch.countDown();
                    System.out.println("getAsync3: "+request.getRequestUri() + " cancelled");
                }

            });
            latch.await();
        } catch (IOException | InterruptedException e) {
            throw new RuntimeException(e);
        }
        return null;

    }
}

输出结果：

getAsync1:/get->200
getAsync2:/get->200
getAsync3: 开始响应....
getAsync3: 收到数据....
getAsync3: 收到数据....
getAsync3: 收到数据....
getAsync3: 接收完毕...
getAsync3: /get->200

HttpClient 5 获取 Cookie

请求 http://httpbin.org/cookies/set/cookieName/www.wdbyte.com 的响应中会带有一个Cookie 信息，其中 name 为 cookieName，value 为 www.wdbyte.com，我们以此用作测试。

Postman 请求测试，可以看到响应了 Cookie 信息。

下面编写 Java 代码进行请求测试

package com.wdbyte.httpclient;

import java.util.List;

import org.apache.hc.client5.http.classic.methods.HttpGet;
import org.apache.hc.client5.http.cookie.BasicCookieStore;
import org.apache.hc.client5.http.cookie.Cookie;
import org.apache.hc.client5.http.cookie.CookieStore;
import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;
import org.apache.hc.client5.http.impl.classic.CloseableHttpResponse;
import org.apache.hc.client5.http.impl.classic.HttpClients;
import org.apache.hc.client5.http.impl.cookie.BasicClientCookie;
import org.apache.hc.client5.http.protocol.HttpClientContext;
import org.apache.hc.core5.http.io.entity.EntityUtils;

/**
 * 这个例子演示了使用本地HTTP上下文填充, 自定义属性
 */
public class HttpClient5WithCookie {

    public static void main(final String[] args) throws Exception {
        try (final CloseableHttpClient httpclient = HttpClients.createDefault()) {
            // 创建一个本地的 Cookie 存储
            final CookieStore cookieStore = new BasicCookieStore();
            // BasicClientCookie clientCookie = new BasicClientCookie("name", "www.wdbyte.com");
            // clientCookie.setDomain("http://httpbin.org/cookies");
            // 过期时间
            // clientCookie.setExpiryDate(new Date());
            // 添加到本地 Cookie
            // cookieStore.addCookie(clientCookie);

            // 创建本地 HTTP 请求上下文 HttpClientContext
            final HttpClientContext localContext = HttpClientContext.create();
            // 绑定 cookieStore 到 localContext
            localContext.setCookieStore(cookieStore);

            final HttpGet httpget = new HttpGet("http://httpbin.org/cookies/set/cookieName/www.wdbyte.com");
            System.out.println("执行请求 " + httpget.getMethod() + " " + httpget.getUri());

            // 获取 Coolie 信息
            try (final CloseableHttpResponse response = httpclient.execute(httpget, localContext)) {
                System.out.println("----------------------------------------");
                System.out.println(response.getCode() + " " + response.getReasonPhrase());
                final List<Cookie> cookies = cookieStore.getCookies();
                for (int i = 0; i < cookies.size(); i++) {
                    System.out.println("Local cookie: " + cookies.get(i));
                }
                EntityUtils.consume(response.getEntity());
            }
        }
    }

}

输出结果：

执行请求 GET http://httpbin.org/cookies/set/cookieName/www.wdbyte.com
----------------------------------------
200 OK
Local cookie: [name: cookieName; value: www.wdbyte.com; domain: httpbin.org; path: /; expiry: null]

HttpClient 5 读取文件内容请求

准备一个 JSON 内容格式的文件 params.json。

{"name":"www.wdbyte.com"}

读取这个文件作为请求参数发起请求。

package com.wdbyte.httpclient;

import java.io.File;
import java.io.FileInputStream;

import org.apache.hc.client5.http.classic.methods.HttpPost;
import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;
import org.apache.hc.client5.http.impl.classic.CloseableHttpResponse;
import org.apache.hc.client5.http.impl.classic.HttpClients;
import org.apache.hc.core5.http.ContentType;
import org.apache.hc.core5.http.io.entity.EntityUtils;
import org.apache.hc.core5.http.io.entity.FileEntity;
import org.apache.hc.core5.http.io.entity.InputStreamEntity;

/**
 * 加载数据流作为 POST 请求参数
 */
public class HttpClient5ChunkEncodedPost {

    public static void main(final String[] args) throws Exception {
        String params = "/Users/darcy/params.json";

        try (final CloseableHttpClient httpclient = HttpClients.createDefault()) {
            final HttpPost httppost = new HttpPost("http://httpbin.org/post");

            final InputStreamEntity reqEntity = new InputStreamEntity(new FileInputStream(params), -1,
                ContentType.APPLICATION_JSON);
            // 也可以使用 FileEntity 的形式
            // FileEntity reqEntity = new FileEntity(new File(params), ContentType.APPLICATION_JSON);

            httppost.setEntity(reqEntity);

            System.out.println("执行请求 " + httppost.getMethod() + " " + httppost.getUri());
            try (final CloseableHttpResponse response = httpclient.execute(httppost)) {
                System.out.println("----------------------------------------");
                System.out.println(response.getCode() + " " + response.getReasonPhrase());
                System.out.println(EntityUtils.toString(response.getEntity()));
            }
        }
    }
}

输出结果：

执行请求 POST http://httpbin.org/post
----------------------------------------
200 OK
{
  "args": {}, 
  "data": "{\"name\":\"www.wdbyte.com\"}\n", 
  "files": {}, 
  "form": {}, 
  "headers": {
    "Accept-Encoding": "gzip, x-gzip, deflate", 
    "Content-Length": "26", 
    "Content-Type": "application/json; charset=UTF-8", 
    "Host": "httpbin.org", 
    "User-Agent": "Apache-HttpClient/5.1.3 (Java/1.8.0_151)", 
    "X-Amzn-Trace-Id": "Root=1-62ee4d95-1f956d4303cea09c52694c86"
  }, 
  "json": {
    "name": "www.wdbyte.com"
  }, 
  "origin": "42.120.74.238", 
  "url": "http://httpbin.org/post"
}

HttpClient 5 表单登录

表单登录可以理解为发起一个携带了认证信息的请求，然后得到响应的 Cookie 的过程。当然这里不仅仅适用于表单登录，也可以是简单的发起一个携带了表单信息的请求。

本应该使用 POST 请求发送表单参数测试，但是在 httpbin.org 中没有对应的接口用于测试，所以这里换成了 GET 请求

示例代码：

package com.wdbyte.httpclient;

import java.util.ArrayList;
import java.util.List;

import org.apache.hc.client5.http.classic.methods.HttpGet;
import org.apache.hc.client5.http.cookie.BasicCookieStore;
import org.apache.hc.client5.http.cookie.Cookie;
import org.apache.hc.client5.http.entity.UrlEncodedFormEntity;
import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;
import org.apache.hc.client5.http.impl.classic.CloseableHttpResponse;
import org.apache.hc.client5.http.impl.classic.HttpClients;
import org.apache.hc.core5.http.HttpEntity;
import org.apache.hc.core5.http.NameValuePair;
import org.apache.hc.core5.http.io.entity.EntityUtils;
import org.apache.hc.core5.http.message.BasicNameValuePair;

/**
 * 演示基于表单的登录
 * 
 * @author https://www.wdbyte.com
 */
public class HttpClient5FormLogin {

    public static void main(final String[] args) throws Exception {
        final BasicCookieStore cookieStore = new BasicCookieStore();
        try (final CloseableHttpClient httpclient = HttpClients.custom()
                .setDefaultCookieStore(cookieStore)
                .build()) {

            // 本应该使用 POST 请求发送表单参数，但是在 httpbin.org 中没有对应的接口用于测试，所以这里换成了 GET 请求
            // HttpPost httpPost = new HttpPost("http://httpbin.org/cookies/set/username/wdbyte.com");
            HttpGet httpPost = new HttpGet("http://httpbin.org/cookies/set/username/wdbyte.com");
            // POST 表单请求参数
            List<NameValuePair> nvps = new ArrayList<>();
            nvps.add(new BasicNameValuePair("username", "wdbyte.com"));
            nvps.add(new BasicNameValuePair("password", "secret"));
            httpPost.setEntity(new UrlEncodedFormEntity(nvps));

            try (final CloseableHttpResponse response2 = httpclient.execute(httpPost)) {
                final HttpEntity entity = response2.getEntity();

                System.out.println("Login form get: " + response2.getCode() + " " + response2.getReasonPhrase());
                System.out.println("当前响应信息 "+EntityUtils.toString(entity));;

                System.out.println("Post 登录 Cookie:");
                final List<Cookie> cookies = cookieStore.getCookies();
                if (cookies.isEmpty()) {
                    System.out.println("None");
                } else {
                    for (int i = 0; i < cookies.size(); i++) {
                        System.out.println("- " + cookies.get(i));
                    }
                }
            }
        }
    }
}

输出结果：

Login form get: 200 OK
当前响应信息 {
  "cookies": {
    "username": "wdbyte.com"
  }
}

Post 登录 Cookie:
- [name: username; value: wdbyte.com; domain: httpbin.org; path: /; expiry: null]

HttpClient 5 Basic Authorization

HTTP 基本认证（Basic Authorization）是一种比较简单的认证实现，主要流程如下

1. 请求一个需要进行基本认证的 HTTP 接口，但是没有携带认证信息。
2. 此时会响应 401 状态码，并在响应 header 中的 WWW-Authenticate 提示需要进行基本认证。
3. 用户把需要提交认证信息进行冒号拼接，然后进行 base64 编码，再在得到的字符串开头拼接上 Basic 放入请求头 Authorization 中。
4. 认证成功，响应成功。

你可以通过浏览器打开下面这个 URL 进行基本认证测试。

http://httpbin.org/basic-auth/admin/123456

在 Apache HttpClient 5 中的实现方式。

package com.wdbyte.httpclient;

import org.apache.hc.client5.http.auth.AuthScope;
import org.apache.hc.client5.http.auth.UsernamePasswordCredentials;
import org.apache.hc.client5.http.classic.methods.HttpGet;
import org.apache.hc.client5.http.impl.auth.BasicCredentialsProvider;
import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;
import org.apache.hc.client5.http.impl.classic.CloseableHttpResponse;
import org.apache.hc.client5.http.impl.classic.HttpClients;
import org.apache.hc.core5.http.io.entity.EntityUtils;

/**
 * 一个简单的示例,它使用HttpClient执行HTTP请求;
 * 一个需要进行用户身份验证的目标站点。
 */
public class HttpClient5BasicAuthentication {

    public static void main(final String[] args) throws Exception {
        final BasicCredentialsProvider credsProvider = new BasicCredentialsProvider();
        credsProvider.setCredentials(
                new AuthScope("httpbin.org", 80),
                new UsernamePasswordCredentials("admin", "123456".toCharArray()));
        try (final CloseableHttpClient httpclient = HttpClients.custom()
                .setDefaultCredentialsProvider(credsProvider)
                .build()) {
            final HttpGet httpget = new HttpGet("http://httpbin.org/basic-auth/admin/123456");

            System.out.println("执行请求" + httpget.getMethod() + " " + httpget.getUri());
            try (final CloseableHttpResponse response = httpclient.execute(httpget)) {
                System.out.println("----------------------------------------");
                System.out.println(response.getCode() + " " + response.getReasonPhrase());
                System.out.println(EntityUtils.toString(response.getEntity()));
            }
        }
    }
}

输出结果：

执行请求GET http://httpbin.org/basic-auth/user/passwd
----------------------------------------
200 OK
{
  "authenticated": true, 
  "user": "user"
}

通过抓包可以看到完整的 HTTP 请求响应过程。

// 请求
GET /basic-auth/user/passwd HTTP/1.1
Accept-Encoding: gzip, x-gzip, deflate
Host: httpbin.org
Connection: keep-alive
User-Agent: Apache-HttpClient/5.1.3 (Java/1.8.0_151)
// 响应
HTTP/1.1 401 UNAUTHORIZED
Date: Sat, 06 Aug 2022 08:25:33 GMT
Content-Length: 0
Connection: keep-alive
Server: gunicorn/19.9.0
WWW-Authenticate: Basic realm="Fake Realm"
Access-Control-Allow-Origin: *
Access-Control-Allow-Credentials: true
// 请求
GET /basic-auth/user/passwd HTTP/1.1
Host: httpbin.org
Connection: keep-alive
User-Agent: Apache-HttpClient/5.1.3 (Java/1.8.0_151)
Authorization: Basic dXNlcjpwYXNzd2Q=
// 响应
HTTP/1.1 200 OK
Date: Sat, 06 Aug 2022 08:25:33 GMT
Content-Type: application/json
Content-Length: 47
Connection: keep-alive
Server: gunicorn/19.9.0
Access-Control-Allow-Origin: *
Access-Control-Allow-Credentials: true

{
  "authenticated": true, 
  "user": "user"
}

HttpClient 5 Digest Authorization

HTTP Basic Authorization 的缺点显而易见，密码通过明文传输存在一定的安全风险，Digest Authorization 认证方式解决了明文传输的问题，这里不过多介绍 Digest 的相关内容，通过一个图简单的示意 Digest 认证方式的流程。

Digest 认证流程

下面是代码演示。

package com.wdbyte.httpclient;

import org.apache.hc.client5.http.auth.AuthExchange;
import org.apache.hc.client5.http.auth.AuthScheme;
import org.apache.hc.client5.http.auth.AuthScope;
import org.apache.hc.client5.http.auth.UsernamePasswordCredentials;
import org.apache.hc.client5.http.classic.methods.HttpGet;
import org.apache.hc.client5.http.impl.auth.BasicCredentialsProvider;
import org.apache.hc.client5.http.impl.auth.DigestScheme;
import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;
import org.apache.hc.client5.http.impl.classic.CloseableHttpResponse;
import org.apache.hc.client5.http.impl.classic.HttpClients;
import org.apache.hc.client5.http.protocol.HttpClientContext;
import org.apache.hc.core5.http.HttpHost;
import org.apache.hc.core5.http.io.entity.EntityUtils;

/**
 *
 * HttpClient如何验证多个请求的示例
 * 使用相同的摘要方案。在初始请求/响应交换之后
 * 共享相同执行上下文的所有后续请求都可以重用
 * 要向服务器进行身份验证的最后一个摘要nonce值。
 */
public class HttpClient5PreemptiveDigestAuthentication {

    public static void main(final String[] args) throws Exception {
        try (final CloseableHttpClient httpclient = HttpClients.createDefault()) {

            final HttpHost target = new HttpHost("http", "httpbin.org", 80);

            final HttpClientContext localContext = HttpClientContext.create();
            final BasicCredentialsProvider credentialsProvider = new BasicCredentialsProvider();
            credentialsProvider.setCredentials(
                    new AuthScope(target),
                    new UsernamePasswordCredentials("admin", "123456".toCharArray()));
            localContext.setCredentialsProvider(credentialsProvider);

            final HttpGet httpget = new HttpGet("http://httpbin.org/digest-auth/auth/admin/123456");

            System.out.println("执行请求 " + httpget.getMethod() + " " + httpget.getUri());
            for (int i = 0; i < 2; i++) {
                try (final CloseableHttpResponse response = httpclient.execute(target, httpget, localContext)) {
                    System.out.println("----------------------------------------");
                    System.out.println(response.getCode() + " " + response.getReasonPhrase());
                    EntityUtils.consume(response.getEntity());

                    final AuthExchange authExchange = localContext.getAuthExchange(target);
                    if (authExchange != null) {
                        final AuthScheme authScheme = authExchange.getAuthScheme();
                        if (authScheme instanceof DigestScheme) {
                            final DigestScheme digestScheme = (DigestScheme) authScheme;
                            System.out.println("Nonce: " + digestScheme.getNonce() +
                                    "; count: " + digestScheme.getNounceCount());
                        }
                    }
                }
            }
        }
    }

}

通过抓包工具可以清晰的看到 2 次请求的流程，在最后一次请求中，直接共享了认证信息，没有再次的重新认证的流程。

// 1. 请求
GET /digest-auth/auth/admin/123456 HTTP/1.1
Accept-Encoding: gzip, x-gzip, deflate
Host: httpbin.org
Connection: keep-alive
User-Agent: Apache-HttpClient/5.1.3 (Java/1.8.0_151)
// 2. 详情，提示认证，给出参数
HTTP/1.1 401 UNAUTHORIZED
Date: Fri, 12 Aug 2022 07:11:06 GMT
Content-Type: text/html; charset=utf-8
Content-Length: 0
Connection: keep-alive
Server: gunicorn/19.9.0
WWW-Authenticate: Digest realm="me@kennethreitz.com", nonce="8dc5e7974a86a6fcc3cf73230b0c4a93", qop="auth", opaque="64b7f68b386c3acc38131f7472aa2079", algorithm=MD5, stale=FALSE
Set-Cookie: stale_after=never; Path=/
Set-Cookie: fake=fake_value; Path=/
Access-Control-Allow-Origin: *
Access-Control-Allow-Credentials: true
// 3. 参数+密码 加密后再次请求
GET /digest-auth/auth/admin/123456 HTTP/1.1
Host: httpbin.org
Connection: keep-alive
User-Agent: Apache-HttpClient/5.1.3 (Java/1.8.0_151)
Cookie: fake=fake_value; stale_after=never
Authorization: Digest username="admin", realm="me@kennethreitz.com", nonce="8dc5e7974a86a6fcc3cf73230b0c4a93", uri="/digest-auth/auth/admin/123456", response="7c6726f8ac54c1ba28e19c71b2fc7338", qop=auth, nc=00000001, cnonce="2fa61501d47a9d39", algorithm=MD5, opaque="64b7f68b386c3acc38131f7472aa2079"
// 4. 认证成功，响应
HTTP/1.1 200 OK
Date: Fri, 12 Aug 2022 07:11:08 GMT
Content-Type: application/json
Content-Length: 48
Connection: keep-alive
Server: gunicorn/19.9.0
Set-Cookie: fake=fake_value; Path=/
Set-Cookie: stale_after=never; Path=/
Access-Control-Allow-Origin: *
Access-Control-Allow-Credentials: true

{
  "authenticated": true, 
  "user": "admin"
}
// 5. 再次请求，共享了登录状态。
GET /digest-auth/auth/admin/123456 HTTP/1.1
Accept-Encoding: gzip, x-gzip, deflate
Host: httpbin.org
Connection: keep-alive
User-Agent: Apache-HttpClient/5.1.3 (Java/1.8.0_151)
Cookie: fake=fake_value; stale_after=never
Authorization: Digest username="admin", realm="me@kennethreitz.com", nonce="8dc5e7974a86a6fcc3cf73230b0c4a93", uri="/digest-auth/auth/admin/123456", response="9955ac79f6a51a876a326449447f549d", qop=auth, nc=00000002, cnonce="2fa61501d47a9d39", algorithm=MD5, opaque="64b7f68b386c3acc38131f7472aa2079"
// 5. 认证成功，响应
HTTP/1.1 200 OK
Date: Fri, 12 Aug 2022 07:11:09 GMT
Content-Type: application/json
Content-Length: 48
Connection: keep-alive
Server: gunicorn/19.9.0
Set-Cookie: fake=fake_value; Path=/
Set-Cookie: stale_after=never; Path=/
Access-Control-Allow-Origin: *
Access-Control-Allow-Credentials: true

{
  "authenticated": true, 
  "user": "admin"
}

HttpClient 5 拦截器

HttpClient 5 中的拦截器可以对请求过程的各个阶段进行拦截处理，通过 HttpClientBuilder 中的关于 Interceptor 的方法可以看到可以进行拦截的节点。

HttpClient5 拦截器

下面编写一个示例，发起三次请求，每次请求都在请求头 herader 中增加一个 request-id 参数，然后对 request-id 值为 2 的请求直接响应 404 结束。

package com.wdbyte.httpclient;

import java.io.IOException;
import java.util.concurrent.atomic.AtomicLong;

import org.apache.hc.client5.http.classic.ExecChain;
import org.apache.hc.client5.http.classic.ExecChain.Scope;
import org.apache.hc.client5.http.classic.ExecChainHandler;
import org.apache.hc.client5.http.classic.methods.HttpGet;
import org.apache.hc.client5.http.impl.ChainElement;
import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;
import org.apache.hc.client5.http.impl.classic.CloseableHttpResponse;
import org.apache.hc.client5.http.impl.classic.HttpClients;
import org.apache.hc.core5.http.ClassicHttpRequest;
import org.apache.hc.core5.http.ClassicHttpResponse;
import org.apache.hc.core5.http.ContentType;
import org.apache.hc.core5.http.EntityDetails;
import org.apache.hc.core5.http.Header;
import org.apache.hc.core5.http.HttpEntity;
import org.apache.hc.core5.http.HttpException;
import org.apache.hc.core5.http.HttpRequest;
import org.apache.hc.core5.http.HttpRequestInterceptor;
import org.apache.hc.core5.http.HttpStatus;
import org.apache.hc.core5.http.io.entity.EntityUtils;
import org.apache.hc.core5.http.io.entity.StringEntity;
import org.apache.hc.core5.http.message.BasicClassicHttpResponse;
import org.apache.hc.core5.http.protocol.HttpContext;

/**
 * 展示如何在请求和响应时进行拦截进行自定义处理。
 */
public class HttpClient5Interceptors {

    public static void main(final String[] args) throws Exception {
        try (final CloseableHttpClient httpclient = HttpClients.custom()
            // 添加一个请求 id 到请求 header
            .addRequestInterceptorFirst(new HttpRequestInterceptor() {
                private final AtomicLong count = new AtomicLong(0);
                @Override
                public void process(
                    final HttpRequest request,
                    final EntityDetails entity,
                    final HttpContext context) throws HttpException, IOException {
                    request.setHeader("request-id", Long.toString(count.incrementAndGet()));
                }
            })
            .addExecInterceptorAfter(ChainElement.PROTOCOL.name(), "custom", new ExecChainHandler() {
                // 请求 id 为 2 的，模拟 404 响应，并自定义响应的内容。
                @Override
                public ClassicHttpResponse execute(
                    final ClassicHttpRequest request,
                    final Scope scope,
                    final ExecChain chain) throws IOException, HttpException {

                    final Header idHeader = request.getFirstHeader("request-id");
                    if (idHeader != null && "2".equalsIgnoreCase(idHeader.getValue())) {
                        final ClassicHttpResponse response = new BasicClassicHttpResponse(HttpStatus.SC_NOT_FOUND,
                            "Oppsie");
                        response.setEntity(new StringEntity("bad luck", ContentType.TEXT_PLAIN));
                        return response;
                    } else {
                        return chain.proceed(request, scope);
                    }
                }
            })
            .build()) {

            for (int i = 0; i < 3; i++) {
                final HttpGet httpget = new HttpGet("http://httpbin.org/get");

                try (final CloseableHttpResponse response = httpclient.execute(httpget)) {
                    System.out.println("----------------------------------------");
                    System.out.println("执行请求 " + httpget.getMethod() + " " + httpget.getUri());
                    System.out.println(response.getCode() + " " + response.getReasonPhrase());
                    System.out.println(EntityUtils.toString(response.getEntity()));
                }
            }
        }
    }

}

输出结果。

----------------------------------------
执行请求 GET http://httpbin.org/get
200 OK
{
  "args": {}, 
  "headers": {
    "Accept-Encoding": "gzip, x-gzip, deflate", 
    "Host": "httpbin.org", 
    "Request-Id": "1", 
    "User-Agent": "Apache-HttpClient/5.1.3 (Java/1.8.0_151)", 
    "X-Amzn-Trace-Id": "Root=1-62f615ba-658ccd42182d22534dbba82c"
  }, 
  "origin": "42.120.75.221", 
  "url": "http://httpbin.org/get"
}

----------------------------------------
执行请求 GET http://httpbin.org/get
404 Oppsie
bad luck
----------------------------------------
执行请求 GET http://httpbin.org/get
200 OK
{
  "args": {}, 
  "headers": {
    "Accept-Encoding": "gzip, x-gzip, deflate", 
    "Host": "httpbin.org", 
    "Request-Id": "3", 
    "User-Agent": "Apache-HttpClient/5.1.3 (Java/1.8.0_151)", 
    "X-Amzn-Trace-Id": "Root=1-62f615bb-4eb6ba10736ace0e21d0cb8c"
  }, 
  "origin": "42.120.75.221", 
  "url": "http://httpbin.org/get"
}

一如既往，文章代码都存放在 Github.com/niumoo/javaNotes[1].