httpclient使用代理ip

在浏览一些网站的时候由于各种原因，无法进行访问。 

频繁访问也可能导致ip被封锁而导致无法访问网站，这在我们爬取数据过程中经常遇到。

这时我们需要通过IE，FireFox进行Http的代理设置， 
当然httpClient也为我们提供这样的设置 。

代理ip用很多种形式，可以找到一个可用Ip或者使用goagent,或者购买代理ip池。

那在httpclicent中要怎么样运用呢。我们以goagent为例。

goagent打开后，只要通过127.0.0.1 端口8087来访问 就可以了

httpclient的具体用法有两种  post和get，具体使用方法可参考:

HTTPClient模块的HttpGet和HttpPost

要调用代理，只需要增加以下代码:

HttpHost proxy = new HttpHost("127.0.0.1",8087, null);
httpclient.getParams().setParameter(ConnRouteParams.DEFAULT_PROXY, proxy);

如果代理需要用户，密码进行验证 

httpClient.getCredentialsProvider().setCredentials(
new AuthScope(proxyHost, proxyPort),
new UsernamePasswordCredentials(userName, password));


完整例子：

public static void main(String args[])
{
StringBuffer sb = new StringBuffer();
//创建HttpClient实例
HttpClient client = getHttpClient();
//创建httpGet
HttpGet httpGet = new HttpGet("http://www.csdn.net");
//执行
try {
HttpResponse response = client.execute(httpGet);

HttpEntity entry = response.getEntity();

if(entry != null)
{
InputStreamReader is = new InputStreamReader(entry.getContent());
BufferedReader br = new BufferedReader(is);
String str = null;
while((str = br.readLine()) != null)
{
sb.append(str.trim());
}
br.close();
}

} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println(sb.toString());
}

//设置代理

public static HttpClient getHttpClient() {

DefaultHttpClient httpClient = new DefaultHttpClient();
String proxyHost = "proxycn2.huawei.com";
int proxyPort = 8080;
String userName = "china\\******";
String password = "*******“
httpClient.getCredentialsProvider().setCredentials(
new AuthScope(proxyHost, proxyPort),
new UsernamePasswordCredentials(userName, password));
HttpHost proxy = new HttpHost(proxyHost,proxyPort);
httpClient.getParams().setParameter(ConnRouteParams.DEFAULT_PROXY, proxy);
return httpClient;
}

导入：commons-logging-1.1.jar，httpclient-4.0-beta2.jar ，httpcore-4.1-alpha1.jar 和 commons-codec-1.4.jar架包