Apache HttpClient4.2入门

 

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。本文使用的HttpClient版本为4.2。

HttpClient 特性

• 基于标准,纯净的java语言.实现了Http1.0和Http1.1
• 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).
• 支持HTTPS协议.
• 通过Http代理建立透明的连接.
• 利用CONNECT 方法通过Http代理建立隧道的https连接.
• Basic, Digest, NTLMv1, NTLMv2, NTLM2 Session, SNPNEGO/Kerberos 认证方案.
• 插件式的自定义认证方案.
• 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.
• 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.
• Automatic Cookie handling for reading Set-Cookie: headers from the server and sending them back out in a Cookie: header when appropriate.
• 插件式的自定义Cookie策略.
• Request output streams to avoid buffering any content body by streaming directly to the socket to the server.
• Response input streams to efficiently read the response body by streaming directly from the socket to the server.
• 在http1.0和http1.1中利用KeepAlive保持持久连接.
• 直接获取服务器发送的response code和 headers.
• 设置连接超时的能力.
• 实验性的支持http1.1 response caching.
• 
  

代码示例

获取HttpClient示例：

public HttpClient getClient() {
		HttpClient client = new DefaultHttpClient();// 获取HttpClient对象
		return client;
	}

HttpClient有多个实现，其中DefaultHttpClient为最常用的。

下面将展示如何使用get和post提交请求，还有如何处理查看response数据

使用get方法请求：

public void doGet(String uri) {// get方法提交
		HttpGet getMethod = null;
		getMethod = new HttpGet(uri);// 获取HttpGet对象，使用该对象提交get请求
	    exctueRequest(getMethod);//执行请求，获取HttpResponse对象

	}

使用post方法请求

public void doPost(String uri,HttpEntity entity) {// post方法提交
		HttpPost postMethod = null;

			postMethod = new HttpPost(uri);
			
			postMethod.setEntity(entity);//设置请求实体，例如表单数据
		    exctueRequest(postMethod); // 执行请求，获取HttpResponse对象
	}

exctueRequest()方法详细说明

private HttpResponse exctueRequest(HttpRequestBase request){
	  HttpResponse response=null;
	  
	  try {
		  log.debug("excute request:"+request.getURI());//获取请求uri
		   log.debug("-----------------------------------");
		response=this.getClient().execute(request);//执行请求，获取HttpResponse对象
		showResponse(response);//打印Response信息
		int statuscode = response.getStatusLine().getStatusCode();//根据相应码处理URI重定向
		if((statuscode == HttpStatus.SC_MOVED_TEMPORARILY) || (statuscode == HttpStatus.SC_MOVED_PERMANENTLY)
				|| (statuscode == HttpStatus.SC_SEE_OTHER) || (statuscode == HttpStatus.SC_TEMPORARY_REDIRECT)){
			
			Header redirectLocation=response.getFirstHeader("Location");//从响应头中获取重定向的uri
			String newuri=redirectLocation.getValue();
		      if((newuri!=null)||(!newuri.equals(""))){
		         log.debug("redirect to "+newuri);
		      request.setURI(new URI(newuri));//重新设置uri
		      response=this.getClient().execute(request);
		      showResponse(response);//打印response信息
		   }else {
			   log.debug("Invalid redirect");
	  }
	  
		}
	} catch (Exception e) {
		e.printStackTrace();
	} finally{
		releaseConnection(request);//释放连接,无论成功与否都需要释放连接
	}
	  return response;
	  
  }

打印响应信息

private void showResponse(HttpResponse response) throws ParseException,
			IOException {
		log.debug("requset result:");
		log.debug(response.getStatusLine().toString());// 响应状态
		log.debug("-----------------------------------");

		Header[] heard = response.getAllHeaders();// 响应头
		log.debug("response heard:");
		for (int i = 0; i < heard.length; i++) {
			log.debug(heard[i]);
		}
		log.debug("-----------------------------------");
		HttpEntity entity = response.getEntity();// 响应实体/内容
		log.debug("response content length:" + entity.getContentLength());
		log.debug("response content:");
		log.debug(EntityUtils.toString(entity));
		
	}

释放连接

private void releaseConnection(HttpRequestBase request) {
		if (request != null) {
			request.releaseConnection();
		}
	}

完整代码

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.URI;
import java.util.ArrayList;
import java.util.List;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.http.Header;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.NameValuePair;
import org.apache.http.ParseException;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.methods.HttpRequestBase;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

public class HttpClientUtil {
	private Log log = LogFactory.getLog(this.getClass());

	public HttpClient getClient() {
		HttpClient client = new DefaultHttpClient();// 获取HttpClient对象
		return client;
	}

	private void releaseConnection(HttpRequestBase request) {
		if (request != null) {
			request.releaseConnection();
		}
	}

	private void showResponse(HttpResponse response) throws ParseException,
			IOException {
		log.debug("requset result:");
		log.debug(response.getStatusLine().toString());// 响应状态
		log.debug("-----------------------------------");

		Header[] heard = response.getAllHeaders();// 响应头
		log.debug("response heard:");
		for (int i = 0; i < heard.length; i++) {
			log.debug(heard[i]);
		}
		log.debug("-----------------------------------");
		HttpEntity entity = response.getEntity();// 响应实体/内容
		log.debug("response content length:" + entity.getContentLength());
		log.debug("response content:");
	
		log.debug(EntityUtils.toString(entity));
		
	}

	public void doGet(String uri) {// get方法提交
		HttpGet getMethod = null;
		getMethod = new HttpGet(uri);// 获取HttpGet对象，使用该对象提交get请求
	    exctueRequest(getMethod);
	}

	public void doPost(String uri,HttpEntity entity) {// post方法提交
		        HttpPost postMethod = null;
			postMethod = new HttpPost(uri);
			postMethod.setEntity(entity);//设置请求实体，例如表单数据
		    exctueRequest(postMethod); // 执行请求，获取HttpResponse对象
		

	}

	private HttpResponse exctueRequest(HttpRequestBase request){
	  HttpResponse response=null;
	  
	  try {
		  log.debug("excute request:"+request.getURI());
		   log.debug("-----------------------------------");
		response=this.getClient().execute(request);//执行请求，获取HttpResponse对象
		showResponse(response);
		int statuscode = response.getStatusLine().getStatusCode();//处理重定向
		if((statuscode == HttpStatus.SC_MOVED_TEMPORARILY) || (statuscode == HttpStatus.SC_MOVED_PERMANENTLY)
				|| (statuscode == HttpStatus.SC_SEE_OTHER) || (statuscode == HttpStatus.SC_TEMPORARY_REDIRECT)){
			
			Header redirectLocation=response.getFirstHeader("Location");
			String newuri=redirectLocation.getValue();
		      if((newuri!=null)||(!newuri.equals(""))){
		         log.debug("redirect to "+newuri);
		      request.setURI(new URI(newuri));
		      response=this.getClient().execute(request);
		      showResponse(response);
		   }else {
			   log.debug("Invalid redirect");
	  }
	  
		}
	} catch (Exception e) {
		e.printStackTrace();
	} finally{
		releaseConnection(request);//释放连接
	}
	  return response;
	  
  }

	public static void main(String[] args) {
		HttpClientUtil client = new HttpClientUtil();
		client.doGet("http://www.baidu.com/s?wd=HttpClient");
		
		List<NameValuePair> formparams = new ArrayList<NameValuePair>();// 设置表格参数
		formparams.add(new BasicNameValuePair("usrname", "admin"));
		formparams.add(new BasicNameValuePair("password", "123456"));
		UrlEncodedFormEntity uefEntity = null;
		try {
			uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8");//获取实体对象
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
		}
		client.doPost("http://localhost:8080/U2_project/login.do",uefEntity);
	}
}