如何建立通过代理来访问的URL？

[myair]

我访问WEB要通过代理服务器 172.20.5.5：8080.

在程序中，一般
URL aURL = new URL("http://www.sina.com.cn");
URLConnection connection=url.openConnection();
connection.connect();
即可。

但我要通过代理服务器的话，是不时还有其它的设置。

否则的话，下载图片的时候，大于10k的都很难下。而文本文件没有多大的关系。

不过下载图片的和下载文本的有区别
//for graphics
DataInputStream in=new DataInputStream(connection.getInputStream());
DataOutputStream out1=new DataOutputStream(new FileOutputStream(downloadPath+filename));
while(in.available()!=0) {
out1.writeByte(in.readByte());
｝
in.close();
out1.close();

//for text
BufferedReader in = new BufferedReader(new InputStreamReader(new DataInputStream(connection.getInputStream())));
PrintWriter out1= new PrintWriter(new BufferedWriter(new FileWriter(downloadPath+filename)));
while((line=in.readLine())!=null) {
}
...

请大家指正。谢谢

[skyyoung]

Connect via socket through a Proxy
You have to set the following properties : proxySet, proxyHost and proxyPort.



This can be done when starting the JVM for a JAVA application : java -DproxySet=true -DproxyHost=myProxyServer.come -DproxyPort=80 MyJavaApp



Or in your source : import java.util.Properties;
...

Properties systemSettings = System.getProperties();
systemSettings.put("proxySet", "true");
systemSettings.put("proxyHost", "myProxyServer.com");
systemSettings.put("proxyPort", "80");
System.setProperties(systemSettings);





--------------------------------------------------------------------------------
NOTE:
You might need to identify yourself to the proxy server. Use the HTTP property "Proxy-Authorization" with a username:password base64 encoded. Properties systemSettings = System.getProperties();
...
System.setProperties(systemSettings);

URL url=new URL("http://someserver/somepage");
URLConnection uc = url.openConnection ();
String encoded = new String(Base64.base64Encode(new String("username:password").getBytes()));
uc.setRequestProperty("Proxy-Authorization", "Basic " + encoded);
uc.connect();

[coolbitf]

帐号，密码，还有一个东西：“域”！！

怎么办？？