How to send response headers from proxy to browser?
- From: "hiwa" <HGA03630@xxxxxxxxxxx>
- Date: 19 Mar 2006 17:59:15 -0800
This question's got no replies on forum.java.sun.com
through its full four days and three nights life.
The proxy server intercepts every request from the
browser and redirect it to www.yahoo.com. It simply
discards original request. After connecting to yahoo.com,
it sends the received response to the browser,
displaying the first part of the yahoo page. However,
as described in the comment on the code below, it
seems the proxy can't send the response headers to
the browser, it only sends document content. What
should we do to send the response headers from proxy?
This program has no practical usefullness. It's only
an exercise for implementing proxy.
/* SimpleProxy.java
* redirect every request from browser to www.yahoo.com
*/
import java.net.*;
import java.io.*;
import java.util.*;
class SimpleProxy{
ServerSocket pxSrvSocket;
Socket clientSocket;
URL remoteUrl;
URLConnection remoteConnection;
BufferedReader readClient, readRemote;
PrintWriter writeClient;
String clientReq, remoteRes, resphName, resphValue, resphStr, resMsg;
Map<String,List<String>> respHdrs; // response headers
List<String> values; // header values
int len;
public SimpleProxy(){
try{
pxSrvSocket = new ServerSocket(9999);
clientSocket = pxSrvSocket.accept();
System.out.println("browser connected to this proxy");
readClient = new BufferedReader
(new InputStreamReader(clientSocket.getInputStream()));
writeClient
= new PrintWriter(clientSocket.getOutputStream(), true);
// setup connection and request headers
// (from Firefox 1.5.0.1 on Linux)
remoteUrl = new URL("http://www.yahoo.com/";);
remoteConnection = remoteUrl.openConnection();
remoteConnection.setAllowUserInteraction(true);
remoteConnection.setDoInput(true);
remoteConnection.setDoOutput(true);
//remoteConnection.setIfModifiedSince(0L);
//remoteConnection.setUseCaches(true);
((HttpURLConnection)remoteConnection).setRequestMethod("GET");
remoteConnection.setRequestProperty("Host", "www.yahoo.com");
remoteConnection.setRequestProperty("User-Agent",
"User-Agent: Mozilla/5.0 (X11; U; Linux i686; ja; rv:1.8.0.1)
Gecko/20060124 Firefox/1.5.0.1");
remoteConnection.setRequestProperty("Accept",
"text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5");
remoteConnection.setRequestProperty("Accept-Language",
"ja,en-us;q=0.7,en;q=0.3");
remoteConnection.setRequestProperty("Accept-Encoding",
"gzip,deflate");
remoteConnection.setRequestProperty("Accept-Charset",
"ISO-8859-1,utf-8;q=0.7,*;q=0.7");
remoteConnection.setRequestProperty("Keep-Alive", "300");
remoteConnection.setRequestProperty("Proxy-Connection",
"keep-alive");
remoteConnection.connect();
System.out.println
("remote connection esatblished : " +
remoteConnection.toString());
readRemote = new BufferedReader
(new InputStreamReader(remoteConnection.getInputStream()));
// dump original request from browser
while ((clientReq = readClient.readLine()).length() > 0){
System.out.println("read from browser : " + clientReq);
}
/*** if we uncoment this part, program doesn't work, only blank screen
***
// get response headers
respHdrs = remoteConnection.getHeaderFields();
Set<String> names = respHdrs.keySet();
// first, write response status line
resphStr = "";
values = respHdrs.get(null);
for (String val : values){
resphStr += val + ","; // e.g. HTTP/1.1 200 OK
}
len = resphStr.length();
if (resphStr.charAt(len - 1) == ','){ // trim last ','
resphStr = resphStr.substring(0, len - 1);
}
System.out.println("resp hdr from remote: " + resphStr);
writeClient.println(resphStr);
// names.remove(null); // UnsupportedOperationException
// next, other response headers
for (String name : names){
if (name != null){
values = respHdrs.get(name);
resphStr = name + ": ";
for (String val : values){
resphStr += val + ",";
}
len = resphStr.length();
if (resphStr.charAt(len - 1) == ','){ // trim last ','
resphStr = resphStr.substring(0, len - 1);
}
System.out.println("resp hdr from remote: " + resphStr);
writeClient.println(resphStr);
}
}
System.out.println();
writeClient.println(); // a blank line
*** end response headers part ***/
// get and write document contents -- this part works normally
// if we comment-out the above part
while((remoteRes = readRemote.readLine()).length() > 0){
writeClient.println(remoteRes);
System.out.println("response from remote : " + remoteRes);
}
writeClient.close();
clientSocket.close();
pxSrvSocket.close();
}catch (IOException e){
e.printStackTrace();
}
}
public static void main(String a[]){
new SimpleProxy();
}
}
.
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