码迷,mamicode.com
首页 > Web开发 > 详细

httpclient的一些学习心得

时间:2015-04-13 12:27:37      阅读:149      评论:0      收藏:0      [点我收藏+]

标签:

最近忙于一个项目,了解下httpclient,在这里总结出来,和大家一起学习分享,希望各位朋友提出宝贵的意见。 

首先介绍一下项目的背景: 
  目标:把国内一家保险公司的“WEB一账通”改成“WAP一账通”。 
  资源:客户不提供任何的webservice接口。 
  
本项目中用到的第三方组件是apache的httpclient,一个非常强大的网页抓取工具(抓这个字用得可能不太好), 这里和大家 
一起讨论下httpclient的一些常用用法和要注意的地方。 

本文引用的资源列表: 

  httpclient入门:  http://www.ibm.com/developerworks/cn/opensource/os-httpclient/ 
  httpclient证书导入:http://www.blogjava.net/happytian/archive/2006/12/22/89447.html 
  httpclient高级认识:http://laohuang.iteye.com/blog/55613 
  httpclient官方文档:http://hc.apache.org/httpcomponents-client/index.html 
  httpclient资源关闭:http://www.iteye.com/topic/234759 
  
  
上面的文章写得很好,看完之后也就知道怎么用httpclient这个很好的工具了,但是在这里还是补充一些比较重要的东西,也是项目中经 
常碰到的问题。 

首先要注意的有以下几点: 
1、httpclient连接后资源释放问题很重要,就跟我们用database connection要释放资源一样。 
2、https网站采用ssl加密传输,证书导入要注意。 
3、做这样的项目最好先了解下http协义,比如302,301,200,404返回代码的含义(这是最基本的),cookie,session的机制。 
4、httpclient的redirect状态默认是自动的,这在很大程度上给开发者很大的方便(如一些授权获得cookie),但是有时要手动管理下,比如 
  有时会遇到CircularRedirectException异常,出现这样的情况是因为返回的头文件中location值指向之前重复(端口号可以不同)地址,导致可能会出现死 
  循环递归重定向,这时可以手动关闭:method.setFollowRedirects(false) 
5、有的网站会先判别用户的请求是否是来自浏览器,如不是,则返回不正确的文本,所以用httpclient抓取信息时在头部加入如下信息: 
  header.put("User-Agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; QQDownload 1.7; .NET CLR 1.1.4322; CIBA; .NET CLR 2.0.50727)"); 
6、当post请求提交数据时要改变默认编码,不然的话提交上去的数据会出现乱码。重写postMethod的setContentCharSet()方法就可以了: 





  
下面写一个通用类来处理request请求返回的文本: 

Java代码  技术分享
/* 
 * HttpRequestProxy.java 
 * 
 * Created on November 3, 2008, 9:53 AM 
 */  
  
package cn.com.mozat.net;  
  
import java.io.BufferedReader;  
import java.io.IOException;  
import java.io.InputStream;  
import java.io.InputStreamReader;  
import java.util.HashMap;  
import java.util.Iterator;  
import java.util.Map;  
import java.util.Set;  
  
import org.apache.commons.httpclient.Header;  
import org.apache.commons.httpclient.HttpClient;  
import org.apache.commons.httpclient.HttpException;  
import org.apache.commons.httpclient.HttpMethod;  
import org.apache.commons.httpclient.NameValuePair;  
import org.apache.commons.httpclient.SimpleHttpConnectionManager;  
import org.apache.commons.httpclient.methods.GetMethod;  
import org.apache.commons.httpclient.methods.PostMethod;  
  
import cn.com.mozat.exception.CustomException;  
  
/** 
 *  
 * @author bird  email:lihongfu-84@163.com 
 * 
 * 2008-11-4  09:49:48 
 */  
public class HttpRequestProxy{  
    //超时间隔  
    private static int connectTimeOut = 60000;  
 //让connectionmanager管理httpclientconnection时是否关闭连接  
    private static boolean alwaysClose = false;  
 //返回数据编码格式  
    private String encoding = "UTF-8";  
      
    private final HttpClient client = new HttpClient(new SimpleHttpConnectionManager(alwaysClose));  
   
    public HttpClient getHttpClient(){  
        return client;  
    }  
        
    /** 
     * 用法: 
     * HttpRequestProxy hrp = new HttpRequestProxy(); 
     * hrp.doRequest("http://www.163.com",null,null,"gbk"); 
     *  
     * @param url  请求的资源URL 
     * @param postData  POST请求时form表单封装的数据 没有时传null 
     * @param header   request请求时附带的头信息(header) 没有时传null 
     * @param encoding response返回的信息编码格式 没有时传null 
     * @return  response返回的文本数据 
     * @throws CustomException  
     */  
    public String doRequest(String url,Map postData,Map header,String encoding) throws CustomException{  
     String responseString = null;  
     //头部请求信息  
     Header[] headers = null;  
     if(header != null){  
      Set entrySet = header.entrySet();  
         int dataLength = entrySet.size();  
          headers= new Header[dataLength];  
         int i = 0;  
         for(Iterator itor = entrySet.iterator();itor.hasNext();){  
          Map.Entry entry = (Map.Entry)itor.next();  
          headers[i++] = new Header(entry.getKey().toString(),entry.getValue().toString());  
         }  
     }  
     //post方式  
        if(postData!=null){  
         PostMethod postRequest = new PostMethod(url.trim());  
         if(headers != null){  
          for(int i = 0;i < headers.length;i++){  
           postRequest.setRequestHeader(headers[i]);  
          }  
         }  
         Set entrySet = postData.entrySet();  
         int dataLength = entrySet.size();  
         NameValuePair[] params = new NameValuePair[dataLength];  
         int i = 0;  
         for(Iterator itor = entrySet.iterator();itor.hasNext();){  
          Map.Entry entry = (Map.Entry)itor.next();  
          params[i++] = new NameValuePair(entry.getKey().toString(),entry.getValue().toString());  
         }  
         postRequest.setRequestBody(params);  
         try {  
    responseString = this.executeMethod(postRequest,encoding);  
   } catch (CustomException e) {  
    throw e;  
   } finally{  
    postRequest.releaseConnection();  
   }  
        }  
      //get方式  
        if(postData == null){  
         GetMethod getRequest = new GetMethod(url.trim());  
         if(headers != null){  
          for(int i = 0;i < headers.length;i++){  
           getRequest.setRequestHeader(headers[i]);  
          }  
         }  
         try {  
    responseString = this.executeMethod(getRequest,encoding);  
   } catch (CustomException e) {  
                e.printStackTrace();  
    throw e;  
   }finally{  
    getRequest.releaseConnection();  
   }  
        }  
   
        return responseString;  
    }  
  
 private String executeMethod(HttpMethod request, String encoding) throws CustomException{  
  String responseContent = null;  
  InputStream responseStream = null;  
  BufferedReader rd = null;  
  try {  
   this.getHttpClient().executeMethod(request);  
   if(encoding != null){  
    responseStream = request.getResponseBodyAsStream();  
     rd = new BufferedReader(new InputStreamReader(responseStream,  
                      encoding));  
              String tempLine = rd.readLine();  
              StringBuffer tempStr = new StringBuffer();  
              String crlf=System.getProperty("line.separator");  
              while (tempLine != null)  
              {  
                  tempStr.append(tempLine);  
                  tempStr.append(crlf);  
                  tempLine = rd.readLine();  
              }  
              responseContent = tempStr.toString();  
   }else  
    responseContent = request.getResponseBodyAsString();  
             
   Header locationHeader = request.getResponseHeader("location");  
   //返回代码为302,301时,表示页面己经重定向,则重新请求location的url,这在  
   //一些登录授权取cookie时很重要  
   if (locationHeader != null) {  
             String redirectUrl = locationHeader.getValue();  
             this.doRequest(redirectUrl, null, null,null);  
         }  
  } catch (HttpException e) {  
   throw new CustomException(e.getMessage());  
  } catch (IOException e) {  
   throw new CustomException(e.getMessage());  
  
  } finally{  
   if(rd != null)  
    try {  
     rd.close();  
    } catch (IOException e) {  
     throw new CustomException(e.getMessage());  
    }  
    if(responseStream != null)  
     try {  
      responseStream.close();  
     } catch (IOException e) {  
      throw new CustomException(e.getMessage());  
  
     }  
  }  
  return responseContent;  
 }  
   
     
 /** 
  * 特殊请求数据,这样的请求往往会出现redirect本身而出现递归死循环重定向 
  * 所以单独写成一个请求方法 
  * 比如现在请求的url为:http://localhost:8080/demo/index.jsp 
  * 返回代码为302 头部信息中location值为:http://localhost:8083/demo/index.jsp 
  * 这时httpclient认为进入递归死循环重定向,抛出CircularRedirectException异常 
  * @param url 
  * @return 
  * @throws CustomException  
  */  
 public String doSpecialRequest(String url,int count,String encoding) throws CustomException{  
  String str = null;  
  InputStream responseStream = null;  
  BufferedReader rd = null;  
  GetMethod getRequest = new GetMethod(url);  
  //关闭httpclient自动重定向动能  
  getRequest.setFollowRedirects(false);  
  try {  
     
   this.client.executeMethod(getRequest);  
   Header header = getRequest.getResponseHeader("location");  
   if(header!= null){  
    //请求重定向后的URL,count同时加1  
    this.doSpecialRequest(header.getValue(),count+1, encoding);  
   }  
   //这里用count作为标志位,当count为0时才返回请求的URL文本,  
   //这样就可以忽略所有的递归重定向时返回文本流操作,提高性能  
   if(count == 0){  
    getRequest = new GetMethod(url);  
    getRequest.setFollowRedirects(false);  
    this.client.executeMethod(getRequest);  
    responseStream = getRequest.getResponseBodyAsStream();  
    rd = new BufferedReader(new InputStreamReader(responseStream,  
                      encoding));  
             String tempLine = rd.readLine();  
             StringBuffer tempStr = new StringBuffer();  
             String crlf=System.getProperty("line.separator");  
             while (tempLine != null)  
             {  
                 tempStr.append(tempLine);  
                 tempStr.append(crlf);  
                 tempLine = rd.readLine();  
             }  
             str = tempStr.toString();  
   }  
     
  } catch (HttpException e) {  
   throw new CustomException(e.getMessage());  
  } catch (IOException e) {  
   throw new CustomException(e.getMessage());  
  } finally{  
   getRequest.releaseConnection();  
   if(rd !=null)  
    try {  
     rd.close();  
    } catch (IOException e) {  
     throw new CustomException(e.getMessage());  
    }  
    if(responseStream !=null)  
     try {  
      responseStream.close();  
     } catch (IOException e) {  
      throw new CustomException(e.getMessage());  
     }  
  }  
  return str;  
 }  
   
   
   
   
 public static void main(String[] args) throws Exception{  
  HttpRequestProxy hrp = new HttpRequestProxy();  
   Map header = new HashMap();  
         header.put("User-Agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; QQDownload 1.7; .NET CLR 1.1.4322; CIBA; .NET CLR 2.0.50727)");  
  String str = hrp.doRequest(  
    "http://www.cma-cgm.com/en/eBusiness/Tracking/Default.aspx?BolNumber=GZ2108827",  
     null, header,null);  
  System.out.println(str.contains("row_CRXU1587647"));  
//  System.out.println(str);  
 }  
     
}  

  

httpclient的一些学习心得

标签:

原文地址:http://www.cnblogs.com/daxiong2014/p/4421739.html

(0)
(0)
   
举报
评论 一句话评论(0
登录后才能评论!
© 2014 mamicode.com 版权所有  联系我们:gaon5@hotmail.com
迷上了代码!