HttpClient jar包使用详解

你的名字 2023-10-16 20:46 84阅读 0赞

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，增加了易用性和灵活性（具体区别，日后我们再讨论），它不仅是客户端发送Http请求变得容易，而且也方便了开发人员测试接口（基于Http协议的），即提高了开发的效率，也方便提高代码的健壮性。因此熟练掌握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入。

## 一、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，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。

下载地址: [http://hc.apache.org/downloads.cgi][http_hc.apache.org_downloads.cgi]

## 二、特性 ##

1. 基于标准、纯净的java语言。实现了Http1.0和Http1.1

2. 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）。

3. 支持HTTPS协议。

4. 通过Http代理建立透明的连接。

5. 利用CONNECT方法通过Http代理建立隧道的https连接。

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

7. 插件式的自定义认证方案。

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. 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。

10. 自动处理Set-Cookie中的Cookie。

11. 插件式的自定义Cookie策略。

12. Request的输出流可以避免流中内容直接缓冲到socket服务器。

13. Response的输入流可以有效的从socket服务器直接读取相应内容。

14. 在http1.0和http1.1中利用KeepAlive保持持久连接。

15. 直接获取服务器发送的response code和 headers。

16. 设置连接超时的能力。

17. 实验性的支持http1.1 response caching。

18. 源代码基于Apache License 可免费获取。

## 三、使用方法 ##

使用HttpClient发送请求、接收响应很简单，一般需要如下几步即可。

1. 创建HttpClient对象。

2. 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。

3. 如果需要发送请求参数，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。程序可通过该对象获取服务器的响应内容。

6. 释放连接。无论执行方法是否成功，都必须释放连接

## 四、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连接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) {
    				}
    			}
    			// 相信自己的CA和所有自签名的证书
    			SSLContext sslcontext = SSLContexts.custom().loadTrustMaterial(trustStore, new TrustSelfSignedStrategy()).build();
    			// 只允许使用TLSv1协议
    			SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(sslcontext, new String[] { "TLSv1" }, null,
    					SSLConnectionSocketFactory.BROWSER_COMPATIBLE_HOSTNAME_VERIFIER);
    			httpclient = HttpClients.custom().setSSLSocketFactory(sslsf).build();
    			// 创建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（模拟用户登录请求）
    	 */
    	public void postForm() {
    		// 创建默认的httpClient实例.  
    		CloseableHttpClient httpclient = HttpClients.createDefault();
    		// 创建httppost  
    		HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action");
    		// 创建参数队列  
    		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 {
    			// 关闭连接,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同返回不同结果
    	 */
    	public void post() {
    		// 创建默认的httpClient实例.  
    		CloseableHttpClient httpclient = HttpClients.createDefault();
    		// 创建httppost  
    		HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action");
    		// 创建参数队列  
    		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 {
    			// 关闭连接,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 {
    			// 创建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 {
    			// 关闭连接,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。该版本与之前的代码写法风格相差较大，大家多留意下。

[http_hc.apache.org_downloads.cgi]: http://hc.apache.org/downloads.cgi