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  2. Httpclient

Httpclient

由 混江龙づ霸主 提交于 2020-12-17 06:05:36

  今天给大家分享的是Httpclient,如有不足，敬请指教。

一、Httpclient简介

1.1 什么是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。实现了所有 HTTP 的方法（GET,POST,PUT,HEAD 等）
  • 下载地址：http://hc.apache.org/

1.2 httpclient作用

  • 在java代码中，发送Http请求。通常用来实现远程接口调用

1.3 HttpClient测试

  • 在工程中添加httpclient的pom依赖。
	<!-- httpclient -->
	<dependency>
		<groupId>org.apache.httpcomponents</groupId>
		<artifactId>httpclient</artifactId>
		<version>4.3.5</version>
	</dependency>

1.3.1 执行GET请求

package com.xkt.test;

import java.io.IOException;

import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

/**
 * 测试HttpClient
 * 
 * @author lzx
 *
 */
public class HttpClientGet {

	public static void main(String[] args) {

		doGet();

	}

	private static void doGet() {

		CloseableHttpClient httpClient = null;

		CloseableHttpResponse response = null;

		try {
			// 1.创建客户端
			httpClient = HttpClients.createDefault();

			// 2.创建get请求
			HttpGet get = new HttpGet("http://www.baidu.com");

			// 3.执行请求
			response = httpClient.execute(get);

			// 4.解析结果
			// 判断返回状态是否为200
			int code = response.getStatusLine().getStatusCode();

			if (200 == code) {

				HttpEntity entity = response.getEntity();

				String str = EntityUtils.toString(entity, "utf-8");

				System.out.println(str);
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			if (null != response) {
				try {
					response.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}

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

	}

}

1.3.2 执行GET带参数

package com.xkt.test;

import java.io.IOException;
import java.net.URI;

import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.utils.URIBuilder;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

/**
 * 测试HttpClient带参数
 * 
 * @author lzx
 *
 */
public class HttpClientGetWithParam {

	public static void main(String[] args) {

		doGetWithParam();

	}

	private static void doGetWithParam() {

		CloseableHttpClient httpClient = null;

		CloseableHttpResponse response = null;

		try {
			// 1.创建客户端
			httpClient = HttpClients.createDefault();

			// 2.创建get请求,当get请求有参数时，就在uri路径上，需要用URIBuilder去构建参数

			URI uri = new URIBuilder("http://www.baidu.com/s").setParameter("wd", "java").build();
			HttpGet get = new HttpGet(uri);

			// 3.执行请求
			response = httpClient.execute(get);

			// 4.解析结果
			// 判断返回状态是否为200
			int code = response.getStatusLine().getStatusCode();

			if (200 == code) {

				HttpEntity entity = response.getEntity();

				String str = EntityUtils.toString(entity, "utf-8");

				System.out.println(str);
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			if (null != response) {
				try {
					response.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}

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

	}

}

1.3.3 执行post请求

package com.xkt.test;

import java.io.IOException;

import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.client.LaxRedirectStrategy;
import org.apache.http.util.EntityUtils;

/**
 * 测试HttpClientPost
 * 
 * @author lzx
 *
 */
public class HttpClientPost {

	public static void main(String[] args) {

		doPost();

	}

	private static void doPost() {

		// 1.创建Httpclient对象
		CloseableHttpClient httpclient = HttpClientBuilder.create().setRedirectStrategy(new LaxRedirectStrategy())
				.build();

		// 2.创建http POST请求
		HttpPost httpPost = new HttpPost("http://www.oschina.net");

		CloseableHttpResponse response = null;

		/**
		 * HTTP/1.1 403 Forbidden 原因： 有些网站，设置了反爬虫机制 解决的办法： 设置请求头，伪装浏览器
		 */
		httpPost.addHeader("user-agent",
				"Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36");

		try {
			// 3.执行请求
			response = httpclient.execute(httpPost);
			System.out.println(response.getStatusLine());
			// 4.解析结果

			// 判断返回状态是否为200
			if (response.getStatusLine().getStatusCode() == 200) {
				String content = EntityUtils.toString(response.getEntity(), "UTF-8");
				System.out.println(content);
			}
		} catch (Exception e) {
			e.printStackTrace();

		} finally {
			if (response != null) {
				try {
					response.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			try {
				httpclient.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}

}

1.3.4 执行post带参数

package com.xkt.test;

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

import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.client.LaxRedirectStrategy;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

/**
 * 测试HttpClientPostWithParam
 * 
 * @author lzx
 *
 */
public class HttpClientPostWithParam {

	public static void main(String[] args) {

		doPostWithParam();

	}

	private static void doPostWithParam() {

		CloseableHttpClient httpclient = null;
		CloseableHttpResponse response = null;

		try {
			// 1、第一步：创建HttpClient客户端
			httpclient = HttpClientBuilder.create().setRedirectStrategy(new LaxRedirectStrategy()).build();

			// 2、第二步：创建post请求方式，如果有参数，需要通过UrlEncodedFormEntity来模拟form表单

			// 设置2个post参数，一个是scope、一个是q
			List<NameValuePair> parameters = new ArrayList<>();
			parameters.add(new BasicNameValuePair("scope", "project"));
			parameters.add(new BasicNameValuePair("q", "mysql"));
			// 构造一个form表单式的实体
			UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(parameters);
			HttpPost post = new HttpPost("http://www.oschina.net/search");
			// 将请求实体设置到httpPost对象中
			post.setEntity(formEntity);

			// 有一些网站（接口）设置了反爬虫机制，禁止httpclient这种工具去请求接口代码
			// 设置请求头，伪装浏览器发送请求,有的网站机制比较健全，可能会不成功
			post.addHeader("user-agent",
					"Mozilla/5.0 (Windows NT 6.3; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36");

			// 3、第三步：执行请求

			response = httpclient.execute(post);

			// 4、第四步：解析结果
			int statusCode = response.getStatusLine().getStatusCode();
			System.out.println(statusCode);
			if (200 == statusCode) {
				HttpEntity entity = response.getEntity();

				String str = EntityUtils.toString(entity, "utf-8");

				System.out.println(str);
			}

		} catch (Exception e) {

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

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

	}
}

1.3.5 封装通用工具类HttpClientUtils

package com.xkt.utils;

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

import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
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.client.utils.URIBuilder;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.impl.client.LaxRedirectStrategy;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

/**
 * 
 * 封装HttpClient工具类
 * 
 * @author Administrator
 *
 */
public class HttpClientUtils {

	public static String doGet(String url, Map<String, String> params) {

		// 获取httpclient客户端
		CloseableHttpClient httpclient = HttpClients.createDefault();

		String resultString = "";

		CloseableHttpResponse response = null;

		try {
			URIBuilder builder = new URIBuilder(url);

			if (null != params) {
				for (String key : params.keySet()) {
					builder.setParameter(key, params.get(key));
				}
			}

			HttpGet get = new HttpGet(builder.build());

			response = httpclient.execute(get);

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

			if (200 == response.getStatusLine().getStatusCode()) {
				HttpEntity entity = response.getEntity();
				resultString = EntityUtils.toString(entity, "utf-8");
			}

		} catch (Exception e) {

			e.printStackTrace();
		} finally {
			if (null != response) {
				try {
					response.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			if (null != httpclient) {
				try {
					httpclient.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}

		return resultString;
	}

	public static String doGet(String url) {
		return doGet(url, null);
	}

	public static String doPost(String url, Map<String, String> params) {
		/**
		 * 在4.0及以上httpclient版本中，post需要指定重定向的策略，如果不指定则按默认的重定向策略。
		 * 
		 * 获取httpclient客户端
		 */
		CloseableHttpClient httpclient = HttpClientBuilder.create().setRedirectStrategy(new LaxRedirectStrategy())
				.build();

		String resultString = "";

		CloseableHttpResponse response = null;

		try {

			HttpPost post = new HttpPost(url);

			List<NameValuePair> paramaters = new ArrayList<>();

			if (null != params) {
				for (String key : params.keySet()) {
					paramaters.add(new BasicNameValuePair(key, params.get(key)));
				}

				UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(paramaters);

				post.setEntity(formEntity);
			}

			/**
			 * HTTP/1.1 403 Forbidden 原因： 有些网站，设置了反爬虫机制 解决的办法： 设置请求头，伪装浏览器
			 */
			post.addHeader("user-agent",
					"Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36");

			response = httpclient.execute(post);

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

			if (200 == response.getStatusLine().getStatusCode()) {
				HttpEntity entity = response.getEntity();
				resultString = EntityUtils.toString(entity, "utf-8");
			}

		} catch (Exception e) {

			e.printStackTrace();
		} finally {
			if (null != response) {
				try {
					response.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			if (null != httpclient) {
				try {
					httpclient.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}

		return resultString;
	}

	public static String doPost(String url) {
		return doPost(url, null);
	}
}

1.4 httpclient常见问题及解决方案

1.4.1 请求参数乱码

  • 设置请求的编码格式：
obj.addHeader("Content-Type","application/x-www-form-urlencoded;charset=UTF-8");

1.4.2 响应HTTP/1.1 403 Forbidden

  • 原因：网站设置了反爬虫机制，禁止非法访问。
  • 解决方案：伪装浏览器。
obj.addHeader("User-Agent"," Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537. 36 (KHTML, like Gecko) Chrome/31.0.1650.63");

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