Apache HttpClient-蒲公英云

一、Apache HttpClient：

　　HttpClient 是 Apache Jakarta Common 下的子项目，用来提供高效的、最新的、功能丰富的支持 HTTP 协议的客户端编程工具包，并且它支持 HTTP 协议最新的版本和建议。HttpClient 已经应用在很多的项目中，比如 Apache Jakarta 上很著名的另外两个开源项目 Cactus 和 HTMLUnit 都使用了 HttpClient。

二、Apache HttpClient 使用流程：

创建 HttpClient 对象。
创建请求方法的实例，并指定请求 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。
如果需要发送请求参数，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。
调用 HttpClient 对象的 execute(HttpUriRequest request) 发送请求，该方法返回一个 HttpResponse。
调用 HttpResponse 的 getAllHeaders()、getHeaders(String name) 等方法可获取服务器的响应头；调用 HttpResponse 的 getEntity() 方法可获取 HttpEntity 对象，该对象包装了服务器的响应内容。程序可通过该对象获取服务器的响应内容。
释放连接。无论执行方法是否成功，都必须释放连接

三、示例：

（1）依赖：

<!-- 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 -->

pom.xml

（2）测试：

public class HttpClientTest {
    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://www.baidu.com");
        // 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();
                }
            }
        }
    }
}

四、工具类：

import org.apache.http.HttpEntity;
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.util.Arrays;
/**
 * HttpClient工具类
 */
public class HttpClientUtils {
    private static final String REQUEST_METHOD_GET = "GET";
    private static final String REQUEST_METHOD_POST = "POST";
    private static final String REQUEST_HEADER_CONNECTION = "keep-alive";
    private static final String REQUEST_HEADER_USER_AGENT = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36";
    /**
     * Get请求
     *
     * @param url 路径
     * @return 字符串
     */
    public static String doGet(String url) {
        String result = HttpClientUtils.getResult("GET", url, null);
        return result;
    }
    /**
     * GET请求
     *
     * @param url    API
     * @param cookie cookie
     * @return json字符串
     */
    public static String doGet(String url, String cookie) {
        String result = HttpClientUtils.getResult("GET", url, cookie);
        return result;
    }
    /**
     * POST请求
     *
     * @param url
     * @param params 请求参数
     * @return json字符串
     */
    public static String doPost(String url, BasicNameValuePair... params) {
        String result = HttpClientUtils.getResult("POST", url, null, params);
        return result;
    }
    /**
     * POST请求
     *
     * @param url
     * @param cookie
     * @param params 请求参数
     * @return json字符串
     */
    public static String doPost(String url, String cookie, BasicNameValuePair... params) {
        String result = HttpClientUtils.getResult("POST", url, cookie, params);
        return result;
    }
    /**
     * 使用HttpClient通过API请求来获得json字符串
     *
     * @param requestMethod 请求方式
     * @param url           请求路径
     * @param cookie        cookie
     * @param params        请求参数
     * @return json字符串
     */
    private static String getResult(String requestMethod, String url, String cookie, BasicNameValuePair... params) {
        CloseableHttpClient httpClient = HttpClients.createDefault();
        CloseableHttpResponse httpResponse = null;
        String result = null;
        try {
            //GET
            if (requestMethod.equals(HttpClientUtils.REQUEST_METHOD_GET)) {
                HttpGet httpGet = new HttpGet(url);
                httpGet.setHeader("Connection", HttpClientUtils.REQUEST_HEADER_CONNECTION);
                httpGet.setHeader("Cookie", cookie);
                httpGet.setHeader("User-Agent", HttpClientUtils.REQUEST_HEADER_USER_AGENT);
                httpResponse = httpClient.execute(httpGet);
            }
            //POST
            else if (requestMethod.equals(HttpClientUtils.REQUEST_METHOD_POST)) {
                HttpPost httpPost = new HttpPost(url);
                httpPost.setHeader("Connection", HttpClientUtils.REQUEST_HEADER_CONNECTION);
                httpPost.setHeader("Cookie", cookie);
                httpPost.setHeader("User-Agent", HttpClientUtils.REQUEST_HEADER_USER_AGENT);
                httpPost.setEntity(new UrlEncodedFormEntity(Arrays.asList(params)));
                httpResponse = httpClient.execute(httpPost);
            }
            //----
            HttpEntity entity = httpResponse.getEntity();
            result = EntityUtils.toString(entity);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (httpClient != null) {
                try {
                    httpClient.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return result;
    }
}