HttpClient的使用

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HttpClient 4.x API常用方法

HttpClient是由Apache HttpComponents™项目负责创建和维护专注于HTTP和相关协议的低级Java组件工具集。该项目在Apache Software Foundation（http://www.apache.org）下运行，是更大的开发人员和用户社区的一部分。

HttpClient的特性

  • 基于标准、纯净的 Java 语言。实现了 HTTP 1.0 和 HTTP 1.1
  • 以可扩展的面向对象的结构实现了 HTTP 全部的方法（GET, POST, PUT, DELETE, HEAD, OPTIONS, and TRACE）。
  • 支持 HTTPS 协议。
  • 通过 HTTP 代理建立透明的连接。
  • 利用 CONNECT 方法通过 HTTP 代理建立隧道的 HTTPS 连接。
  • Basic, Digest, NTLMv1, NTLMv2, NTLM2 Session, SNPNEGO/Kerberos 认证方案。
  • 插件式的自定义认证方案。
  • 便携可靠的套接字工厂使它更容易的使用第三方解决方案。
  • 连接管理器支持多线程应用。支持设置最大连接数，同时支持设置每个主机的最大连接数，发现并关闭过期的连接。
  • 自动处理 Set-Cookie 中的 Cookie。
  • 插件式的自定义 Cookie 策略。
  • Request 的输出流可以避免流中内容直接缓冲到 Socket 服务器。
  • Response 的输入流可以有效的从 Socket 服务器直接读取相应内容。
  • 在 HTTP 1.0 和 HTTP 1.1 中利用 KeepAlive 保持持久连接。
  • 直接获取服务器发送的 response code 和 headers。
  • 设置连接超时的能力。
  • 实验性的支持 HTTP 1.1 response caching。
  • 源代码基于 Apache License 可免费获取。

HttpClient 使用流程

  1. 创建HttpClient对象

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    CloseableHttpClient httpClient = HttpClients.createDefault();

  2. 创建请求方法实例,并制定请求URL。如果需要发送GET请求，创建HttpGet对象，如果需要发送POST请求，创建HttpPost对象

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    Get:
    HttpGet httpGet = new HttpGet("http://apis.juhe.cn/ip/ipNew?ip=112.112.11.11&key=56e8d1ce739a1016392097d58af41af4");
    Post:
    HttpPost httpPost = new HttpPost("http://apis.juhe.cn/ip/ipNew");

  3. 如果要发送请求参数，可调用HttpGet、HttpPost共同的setParams(HttpParams params)方法来添加请求参数；对于HttpPost对象而言，也可调用setEntity(HttpEntity entity)方法来设置请求参数

    HttpClient提供一个UrlEncodedFormEntity()类以方便Post请求传递参数,UrlEncodedFormEntit继承StringEntity类,它提供了四个构造函数

    • UrlEncodedFormEntity(List<? extends NameValuePair> parameters, String charset)
    • UrlEncodedFormEntity(Iterable<? extends NameValuePair> parameters, Charset charset)
    • UrlEncodedFormEntity(List<? extends NameValuePair> parameters)
    • UrlEncodedFormEntity(Iterable<? extends NameValuePair> parameters)

  4. 可以通过调用HttpClient 对象的execute(HttpUriRequest request)方法来发送请求，这个方法返回一个HttpResponse

  5. 调用HttpResponse的getAllHeaders()、getHeaders(String name)等方法可获得服务器的响应头；调用HttpResponer的getEntity方法可获取HttpEntity对象,该对象包装了服务器的响应内容,可通过该对象获取服务器的响应内容

  6. 不管执行方法是否成功,都应该释放链接

使用实例

maven依赖如下:

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<!-- Apache Http Begin -->
<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.5</version>
</dependency>
<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>fluent-hc</artifactId>
    <version>4.5.5</version>
</dependency>
<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpmime</artifactId>
    <version>4.5.5</version>
</dependency>
<!-- Apache Http End -->

创建GET请求:

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public class MyTest {
    public static void main(String[] args) {
        get();
    }

    private static void get() {
        // 创建 HttpClient 客户端
        CloseableHttpClient httpClient = HttpClients.createDefault();

        // 创建 HttpGet 请求
        HttpGet httpGet = new HttpGet("http://localhost:8080/content/page?draw=1&start=0&length=10");
        // 设置长连接
        httpGet.setHeader("Connection", "keep-alive");
        // 设置代理（模拟浏览器版本）
        httpGet.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36");
        // 设置 Cookie
        httpGet.setHeader("Cookie", "UM_distinctid=16442706a09352-0376059833914f-3c604504-1fa400-16442706a0b345; CNZZDATA1262458286=1603637673-1530123020-%7C1530123020; JSESSIONID=805587506F1594AE02DC45845A7216A4");

        CloseableHttpResponse httpResponse = null;
        try {
            // 请求并获得响应结果
            httpResponse = httpClient.execute(httpGet);
            HttpEntity httpEntity = httpResponse.getEntity();
            // 输出请求结果
            System.out.println(EntityUtils.toString(httpEntity));
        } catch (IOException e) {
            e.printStackTrace();
        }

        // 无论如何必须关闭连接
        finally {
            if (httpResponse != null) {
                try {
                    httpResponse.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

            if (httpClient != null) {
                try {
                    httpClient.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

创建POST请求:

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public class MyTest {
    public static void main(String[] args) {
        post();
    }

    private static void post() {
        // 创建 HttpClient 客户端
        CloseableHttpClient httpClient = HttpClients.createDefault();

        // 创建 HttpPost 请求
        HttpPost httpPost = new HttpPost("http://localhost:8080/content/page");
        // 设置长连接
        httpPost.setHeader("Connection", "keep-alive");
        // 设置代理（模拟浏览器版本）
        httpPost.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36");
        // 设置 Cookie
        httpPost.setHeader("Cookie", "UM_distinctid=16442706a09352-0376059833914f-3c604504-1fa400-16442706a0b345; CNZZDATA1262458286=1603637673-1530123020-%7C1530123020; JSESSIONID=805587506F1594AE02DC45845A7216A4");

        // 创建 HttpPost 参数
        List<BasicNameValuePair> params = new ArrayList<BasicNameValuePair>();
        params.add(new BasicNameValuePair("draw", "1"));
        params.add(new BasicNameValuePair("start", "0"));
        params.add(new BasicNameValuePair("length", "10"));

        CloseableHttpResponse httpResponse = null;
        try {
            // 设置 HttpPost 参数
            httpPost.setEntity(new UrlEncodedFormEntity(params, "UTF-8"));
            httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            // 输出请求结果
            System.out.println(EntityUtils.toString(httpEntity));
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        // 无论如何必须关闭连接
        finally {
            try {
                if (httpResponse != null) {
                    httpResponse.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }

            try {
                if (httpClient != null) {
                    httpClient.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

封装出的工具类:

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import org.apache.commons.lang3.StringUtils;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Arrays;

public class HttpClientUtils {
    public static final String CONNECTION = "Connection";
    public static final String USER_AGENT= "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36";

    public static String doGet(String url,String cookie){
        return createRequest(HttpGet.METHOD_NAME,url,cookie);
    }

    public static String doGet(String url){
        return createRequest(HttpGet.METHOD_NAME,url,null);
    }

    private static String createRequest(String method, String url, String cookie, BasicNameValuePair ... basicNameValuePairs){
        CloseableHttpClient closeableHttpClient = HttpClients.createDefault();
        CloseableHttpResponse httpResponse = null;
        String result = null;
        try {
            if (HttpGet.METHOD_NAME.equals(method)) {
                HttpGet httpGet = new HttpGet(url);
                httpGet.setHeader("Connection", CONNECTION);
                httpGet.setHeader("User-Agent", USER_AGENT);
                if (StringUtils.isNotBlank(cookie)) {
                    httpGet.setHeader("Cookie", cookie);
                }
                httpResponse = closeableHttpClient.execute(httpGet);
                result = EntityUtils.toString(httpResponse.getEntity());
            } else if (HttpPost.METHOD_NAME.equals(method)) {
                HttpPost httpPost = new HttpPost();
                httpPost.setHeader("Connection", CONNECTION);
                httpPost.setHeader("User-Agent", USER_AGENT);
                if (StringUtils.isNotBlank(cookie)) {
                    httpPost.setHeader("Cookie", cookie);
                }

                httpPost.setEntity(new UrlEncodedFormEntity(Arrays.asList(basicNameValuePairs), "UTF-8"));

                httpResponse = closeableHttpClient.execute(httpPost);
                System.out.println(httpResponse);
                result = EntityUtils.toString(httpResponse.getEntity());
            }
        }catch (IOException e) {
            e.printStackTrace();
        }finally {
            if (httpResponse!=null){
                try {
                    httpResponse.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (closeableHttpClient!=null) {
                try {
                    closeableHttpClient.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

        }
        return result;
    }
}