完整代码

package com.proj.net;

//导入编码的jar文件
import it.sauronsoftware.base64.Base64;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;


/**
* 非常多公司会对网上进行限制,要通过代理server和口令才干连接外网。<br>
* 这样的方式有非常多优点:<br>
* 1、安全。代理server像一层过滤层;<br>
* 2、节省成本,仅仅须要分配非常少的IP地址就可以;<br>
* 3、对员工上网能够个性化配置,避免有人下载大量数据而造成网络拥堵不堪。<br>
*
* 本文通过一个小案例来介绍怎样在程序里跨过局域网訪问外网。
<br>
* 对于搞网络开发的人来说。不值一提;但对于做JAVA EE应用开发的人来说,能够參考。<br>
*
* @author 王一洋
*
* 2014-10-30
* */
public class Test {
public static void main(String[] args) {
try {
//两种方式设置代理server
//设置代理1
//Proxy proxy = new Proxy(Proxy.Type.HTTP,new InetSocketAddress("", 80));
//设置代理2
System.getProperties().setProperty( "http.proxyHost", "");

System.getProperties().setProperty( "http.proxyPort", "" );

String urlString = "http://blog.csdn.net/";
URL url = new URL(urlString);
//相应第一种设置方式
//HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection(proxy);

HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.setConnectTimeout(1000);
//设置User Agent
urlConnection.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");
//设置訪问的username与password
urlConnection.setRequestProperty( "Proxy-Authorization", "Basic" + Base64.encode("username:password") );
urlConnection.connect();
System.out.print(urlConnection.getResponseCode());
BufferedInputStream bis = new BufferedInputStream(urlConnection.getInputStream());
InputStreamReader isr = new InputStreamReader(bis,"UTF-8");
BufferedReader bufferedReader = new BufferedReader(isr);
String str = "";
StringBuffer buffer = new StringBuffer("");
while((str = bufferedReader.readLine())!=null){
buffer.append(str+"\r\n");
}
System.out.println(buffer);
} catch (Exception e) {
e.printStackTrace();
}
}
}



返回code:200,OK!


​异常Server returned HTTP response code: 403 for URL​

在url.openConnection()后加入:

connection.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");