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
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。
处理request请求返回的文本的通用类：
/*
* 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);
} }
