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Java使用HttpClient库发送请求

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HttpClient介绍

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。

下载和安装

下载地址
http://hc.apache.org/downloads.cgi

下载二进制文件后解压lib文件夹，将jar包复制粘贴到项目目录，右击add to Build Path.
关联源码到httpcomponents-asyncclient-4.1.1-src\httpcomponents-asyncclient-4.1.1\目录即可查看源码。

使用示例

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public static void post() {
	// 创建HttpClient实例对象
	CloseableHttpClient httpclient = HttpClients.createDefault();
	
	// 创建Post请求
	HttpPost httppost = new HttpPost(
			"http://localhost:8080/服务端/servlet/Login");
			
	// 创建参数列表
	List<BasicNameValuePair> formparams = new ArrayList<BasicNameValuePair>();
	formparams.add(new BasicNameValuePair("user", "lisi"));
	formparams.add(new BasicNameValuePair("pwd", "123456"));
	
	UrlEncodedFormEntity uefEntity;
	try {
		uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8");
		
		// 设置廉洁配置
		httppost.setEntity(uefEntity);
		System.out.println("executing request " + httppost.getURI());
		
		// 执行连接操作
		CloseableHttpResponse response = httpclient.execute(httppost);
		try {
			HttpEntity entity = response.getEntity();
			if (entity != null) {
			
			    // 遍历Header
				Header[] allHeaders = response.getAllHeaders();
				for (Header h : allHeaders) {
					System.out
							.println(h.getName() + "  :  " + h.getValue());
				}
				
				// 打印正文
				System.out
						.println("--------------------------------------");
				System.out.println("Response content: "
						+ EntityUtils.toString(entity, "UTF-8"));
				System.out
						.println("--------------------------------------");
			}
		} finally {
			response.close();
		}
	} catch (ClientProtocolException e) {
		e.printStackTrace();
	} catch (UnsupportedEncodingException e1) {
		e1.printStackTrace();
	} catch (IOException e) {
		e.printStackTrace();
	} finally {
		// 关闭连接,释放资源
		try {
			httpclient.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}