Java 代理 更换IP 防止被封

import java.io.BufferedInputStream;
import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;

import org.apache.log4j.Logger;

/** 
 * @author Jason
 * @date  Oct 27, 2010
 * @version 1.0 
 */
public class TestProxyIp  {
	private static final Logger log = Logger.getLogger(TestProxyIp.class);
	
	public static void main(String[] args) throws IOException {
		System.setProperty("http.maxRedirects", "50");
		System.getProperties().setProperty("proxySet", "true");
		// 如果不设置，只要代理IP和代理端口正确,此项不设置也可以
		String ip = "93.91.200.146";
		ip = "221.130.18.5";
		ip = "221.130.23.135";
		ip = "221.130.18.78";
		ip = "221.130.23.134";
		ip = "221.130.18.49";
		ip = "111.1.32.36";
		ip = "221.130.18.49";
		ip = "221.130.18.49";
		System.getProperties().setProperty("http.proxyHost", ip);
		System.getProperties().setProperty("http.proxyPort", "80");
		
		//确定代理是否设置成功
		log.info(getHtml("http://www.ip138.com/ip2city.asp"));
		
	}
	
	private static String getHtml(String address){
		StringBuffer html = new StringBuffer();
		String result = null;
		try{
			URL url = new URL(address);
			URLConnection conn = url.openConnection();
			conn.setRequestProperty("User-Agent","Mozilla/4.0 (compatible; MSIE 7.0; NT 5.1; GTB5; .NET CLR 2.0.50727; CIBA)");
			BufferedInputStream in = new BufferedInputStream(conn.getInputStream());
			
			try{
				String inputLine;
				byte[] buf = new byte[4096];
				int bytesRead = 0;
				while (bytesRead >= 0) {
					inputLine = new String(buf, 0, bytesRead, "ISO-8859-1");
					html.append(inputLine);
					bytesRead = in.read(buf);
					inputLine = null;
				}
				buf = null;
			}finally{
				in.close();
				conn = null;
				url = null;
			}
			result = new String(html.toString().trim().getBytes("ISO-8859-1"), "gb2312").toLowerCase();
			
		}catch (Exception e) {
			e.printStackTrace();
			return null;
		}finally{
			html = null;			
		}
		return result;
	}
}

使用动态IP需要注意的地方：
1、如果动态IP错误，会以本机网络IP访问。如果端口错误，会报错。
2、代理IP哪里来呢？ 我是从优易ip代理软件免费IP里找的，然后存到自己本机。如果对方封了我现在的IP，那么我就更换IP。

可参考：http://justdo2008.iteye.com/blog/796290