HttpClient使用详解

Http协议的重要性相信不用我多说了,HttpClient相比传统JDK自带的URLConnection,增长了易用性和灵活性(具体区别,往后咱们再讨论),它不只是客户端发送Http请求变得容易,并且也方便了开发人员测试接口(基于Http协议的),即提升了开发的效率,也方便提升代码的健壮性。所以熟练掌握HttpClient是很重要的必修内容,掌握HttpClient后,相信对于Http协议的了解会更加深刻。 java

1、简介

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,而且它支持HTTP协议最新的版本和建议。HttpClient已经应用在不少的项目中,好比Apache Jakarta上很著名的另外两个开源项目Cactus和HTMLUnit都使用了HttpClient。 apache

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

2、特性

1. 基于标准、纯净的java语言。实现了Http1.0和Http1.1 tomcat

2. 以可扩展的面向对象的结构实现了Http所有的方法(GET, POST, PUT, DELETE, HEAD, OPTIONS, and TRACE)。 服务器

3. 支持HTTPS协议。 多线程

4. 经过Http代理创建透明的链接。 socket

5. 利用CONNECT方法经过Http代理创建隧道的https链接。 工具

6. Basic, Digest, NTLMv1, NTLMv2, NTLM2 Session, SNPNEGO/Kerberos认证方案。 post

7. 插件式的自定义认证方案。 测试

8. 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。

9. 链接管理器支持多线程应用。支持设置最大链接数,同时支持设置每一个主机的最大链接数,发现并关闭过时的链接。

10. 自动处理Set-Cookie中的Cookie。

11. 插件式的自定义Cookie策略。

12. Request的输出流能够避免流中内容直接缓冲socket服务器。

13. Response的输入流能够有效的从socket服务器直接读取相应内容。

14. 在http1.0和http1.1中利用KeepAlive保持持久链接。

15. 直接获取服务器发送的response code和 headers。

16. 设置链接超时的能力。

17. 实验性的支持http1.1 response caching。

18. 源代码基于Apache License 可免费获取。

3、使用方法

使用HttpClient发送请求、接收响应很简单,通常须要以下几步便可。

1. 建立HttpClient对象。

2. 建立请求方法的实例,并指定请求URL。若是须要发送GET请求,建立HttpGet对象;若是须要发送POST请求,建立HttpPost对象。

3. 若是须要发送请求参数,可调用HttpGet、HttpPost共同的setParams(HetpParams 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。

4. 调用HttpClient对象的execute(HttpUriRequest request)发送请求,该方法返回一个HttpResponse。

5. 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。程序可经过该对象获取服务器的响应内容。

6. 释放链接。不管执行方法是否成功,都必须释放链接

4、实例

package com.test;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.security.KeyManagementException;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.cert.CertificateException;
import java.util.ArrayList;
import java.util.List;

import javax.net.ssl.SSLContext;

import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.ParseException;
import org.apache.http.client.ClientProtocolException;
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.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.conn.ssl.SSLContexts;
import org.apache.http.conn.ssl.TrustSelfSignedStrategy;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.mime.MultipartEntityBuilder;
import org.apache.http.entity.mime.content.FileBody;
import org.apache.http.entity.mime.content.StringBody;
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 org.junit.Test;

public class HttpClientTest {

	@Test
	public void jUnitTest() {
		get();
	}

	/**
	 * HttpClient链接SSL
	 */
	public void ssl() {
		CloseableHttpClient httpclient = null;
		try {
			KeyStore trustStore = KeyStore.getInstance(KeyStore.getDefaultType());
			FileInputStream instream = new FileInputStream(new File("d:\\tomcat.keystore"));
			try {
				// 加载keyStore d:\\tomcat.keystore  
				trustStore.load(instream, "123456".toCharArray());
			} catch (CertificateException e) {
				e.printStackTrace();
			} finally {
				try {
					instream.close();
				} catch (Exception ignore) {
				}
			}
			// 相信本身的CA和全部自签名的证书
			SSLContext sslcontext = SSLContexts.custom().loadTrustMaterial(trustStore, new TrustSelfSignedStrategy()).build();
			// 只容许使用TLSv1协议
			SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(sslcontext, new String[] { "TLSv1" }, null,
					SSLConnectionSocketFactory.BROWSER_COMPATIBLE_HOSTNAME_VERIFIER);
			httpclient = HttpClients.custom().setSSLSocketFactory(sslsf).build();
			// 建立http请求(get方式)
			HttpGet httpget = new HttpGet("https://localhost:8443/myDemo/Ajax/serivceJ.action");
			System.out.println("executing request" + httpget.getRequestLine());
			CloseableHttpResponse response = httpclient.execute(httpget);
			try {
				HttpEntity entity = response.getEntity();
				System.out.println("----------------------------------------");
				System.out.println(response.getStatusLine());
				if (entity != null) {
					System.out.println("Response content length: " + entity.getContentLength());
					System.out.println(EntityUtils.toString(entity));
					EntityUtils.consume(entity);
				}
			} finally {
				response.close();
			}
		} catch (ParseException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} catch (KeyManagementException e) {
			e.printStackTrace();
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		} catch (KeyStoreException e) {
			e.printStackTrace();
		} finally {
			if (httpclient != null) {
				try {
					httpclient.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}

	/**
	 * post方式提交表单(模拟用户登陆请求)
	 */
	public void postForm() {
		// 建立默认的httpClient实例.  
		CloseableHttpClient httpclient = HttpClients.createDefault();
		// 建立httppost  
		HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action");
		// 建立参数队列  
		List<namevaluepair> formparams = new ArrayList<namevaluepair>();
		formparams.add(new BasicNameValuePair("username", "admin"));
		formparams.add(new BasicNameValuePair("password", "123456"));
		UrlEncodedFormEntity uefEntity;
		try {
			uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8");
			httppost.setEntity(uefEntity);
			System.out.println("executing request " + httppost.getURI());
			CloseableHttpResponse response = httpclient.execute(httppost);
			try {
				HttpEntity entity = response.getEntity();
				if (entity != null) {
					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 {
			// 关闭链接,释放资源  
			try {
				httpclient.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

	/**
	 * 发送 post请求访问本地应用并根据传递参数不一样返回不一样结果
	 */
	public void post() {
		// 建立默认的httpClient实例.  
		CloseableHttpClient httpclient = HttpClients.createDefault();
		// 建立httppost  
		HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action");
		// 建立参数队列  
		List<namevaluepair> formparams = new ArrayList<namevaluepair>();
		formparams.add(new BasicNameValuePair("type", "house"));
		UrlEncodedFormEntity uefEntity;
		try {
			uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8");
			httppost.setEntity(uefEntity);
			System.out.println("executing request " + httppost.getURI());
			CloseableHttpResponse response = httpclient.execute(httppost);
			try {
				HttpEntity entity = response.getEntity();
				if (entity != null) {
					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 {
			// 关闭链接,释放资源  
			try {
				httpclient.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

	/**
	 * 发送 get请求
	 */
	public void get() {
		CloseableHttpClient httpclient = HttpClients.createDefault();
		try {
			// 建立httpget.  
			HttpGet httpget = new HttpGet("http://www.baidu.com/");
			System.out.println("executing request " + httpget.getURI());
			// 执行get请求.  
			CloseableHttpResponse response = httpclient.execute(httpget);
			try {
				// 获取响应实体  
				HttpEntity entity = response.getEntity();
				System.out.println("--------------------------------------");
				// 打印响应状态  
				System.out.println(response.getStatusLine());
				if (entity != null) {
					// 打印响应内容长度  
					System.out.println("Response content length: " + entity.getContentLength());
					// 打印响应内容  
					System.out.println("Response content: " + EntityUtils.toString(entity));
				}
				System.out.println("------------------------------------");
			} finally {
				response.close();
			}
		} catch (ClientProtocolException e) {
			e.printStackTrace();
		} catch (ParseException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			// 关闭链接,释放资源  
			try {
				httpclient.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

	/**
	 * 上传文件
	 */
	public void upload() {
		CloseableHttpClient httpclient = HttpClients.createDefault();
		try {
			HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceFile.action");

			FileBody bin = new FileBody(new File("F:\\image\\sendpix0.jpg"));
			StringBody comment = new StringBody("A binary file of some kind", ContentType.TEXT_PLAIN);

			HttpEntity reqEntity = MultipartEntityBuilder.create().addPart("bin", bin).addPart("comment", comment).build();

			httppost.setEntity(reqEntity);

			System.out.println("executing request " + httppost.getRequestLine());
			CloseableHttpResponse response = httpclient.execute(httppost);
			try {
				System.out.println("----------------------------------------");
				System.out.println(response.getStatusLine());
				HttpEntity resEntity = response.getEntity();
				if (resEntity != null) {
					System.out.println("Response content length: " + resEntity.getContentLength());
				}
				EntityUtils.consume(resEntity);
			} finally {
				response.close();
			}
		} catch (ClientProtocolException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				httpclient.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}
}



本实例是采用HttpClient4.3最新版本。该版本与以前的代码写法风格相差较大,你们多留意下。
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