Apache 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。

 

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

       Mavn坐标

<dependency>
	<groupId>org.apache.httpcomponents</groupId>
	<artifactId>httpclient</artifactId>
	<version>4.3.4</version>
</dependency>

 

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.post跟get请求示例

package com.ickes;

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.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.protocol.HTTP;
import org.apache.http.util.EntityUtils;

public class HttpClientDemo {
    
	public static void main(String[] args) throws Exception  { 
		get();
	}
	
	/**
	 * post方式提交json代码
	 * @throws Exception 
	 */
	public static void postJson() throws Exception{
		//创建默认的httpClient实例. 
		CloseableHttpClient httpclient = null;
		//接收响应结果
		CloseableHttpResponse response = null;
		try {
			//创建httppost
			httpclient = HttpClients.createDefault();  
			String url ="http://192.168.16.36:8081/goSearch/gosuncn/deleteDocs.htm";
			HttpPost httpPost = new HttpPost(url);
			httpPost.addHeader(HTTP.CONTENT_TYPE,"application/x-www-form-urlencoded");
			//参数
			String json ="{'ids':['html1','html2']}";
			StringEntity se = new StringEntity(json);
			se.setContentEncoding("UTF-8");
			se.setContentType("application/json");//发送json需要设置contentType
			httpPost.setEntity(se);
			response = httpclient.execute(httpPost);
			//解析返结果
			HttpEntity entity = response.getEntity(); 
			if(entity != null){
				String resStr = EntityUtils.toString(entity, "UTF-8");    
			    System.out.println(resStr);
			}
		} catch (Exception e) {
			throw e;
		}finally{
			httpclient.close();
		    response.close();
		}
	}
	
	 /** 
     * post方式提交表单（模拟用户登录请求） 
	 * @throws Exception 
     */  
    public static void postForm() throws Exception  {  
        // 创建默认的httpClient实例.    
		CloseableHttpClient httpclient = null;
		//发送请求
		CloseableHttpResponse response = null;
		try {
			httpclient = HttpClients.createDefault();  
			// 创建httppost    
			String url= "http://localhost:8080/search/ajx/user.htm";
			HttpPost httppost = new HttpPost(url);  
			// 创建参数队列    
			List<NameValuePair> formparams = new ArrayList<NameValuePair>();  
			formparams.add(new BasicNameValuePair("username", "admin"));  
			formparams.add(new BasicNameValuePair("password", "123456"));
			//参数转码
			UrlEncodedFormEntity uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8");  
			httppost.setEntity(uefEntity); 
			response = httpclient.execute(httppost);  
			HttpEntity entity = response.getEntity();  
			if (entity != null) {  
			      System.out.println(EntityUtils.toString(entity, "UTF-8"));  
			}  
			//释放连接
		} catch (Exception e) {
			throw e;
		}finally{
			 httpclient.close();
		     response.close();
		}
    }  
    
    /** 
     * 发送 get请求 
     * @throws Exception 
     */  
    public static void get() throws Exception {  
    	CloseableHttpClient httpclient = null;
    	CloseableHttpResponse response = null;
        try {
        	httpclient = HttpClients.createDefault();  
			// 创建httpget.    
			HttpGet httpget = new HttpGet("http://www.baidu.com/");  
			// 执行get请求.    
			response = httpclient.execute(httpget);  
			// 获取响应实体    
			HttpEntity entity = response.getEntity();  
      
			// 打印响应状态    
			System.out.println(response.getStatusLine().getStatusCode());  
			if (entity != null) {  
			    // 打印响应内容    
			    System.out.println("Response content: " + EntityUtils.toString(entity));  
			}
		} catch (Exception e) {
			throw e;
		}finally{
			httpclient.close();
			response.close();
		}
    }
}

 

 

五、SSL跟上传文件实例

 

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() {
		ssl();
	}

	/**
	 * 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();
				}
			}
		}
	}

	/**
	 * 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。

 

参考：http://blog.csdn.net/wangpeng047/article/details/19624529