Solved

How to read GZIP and Chunked HTTP file by java

Posted on 2008-06-10
25
1,564 Views
Last Modified: 2013-11-22
I am writing a personal small web browser by using Java. How can I read a file that contains ASCII text, compressed (by gzip) and chunked data file?
0
Comment
Question by:guochu
  • 13
  • 9
25 Comments
 
LVL 13

Expert Comment

by:MicheleMarcon
ID: 21757267
for GZIP

http://java.sun.com/j2se/1.4.2/docs/api/java/util/zip/package-summary.html

for chunked data use byte buffers

for text... well use String or StringBuffer ;)
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 21757813
The HttpClient lilbrary can handle this afaik

http://hc.apache.org/httpclient-3.x/
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 21758066
It could be that it's not handled transparently though. Here is an example using the aforementioned API that wraps a POST method. Something similar could easily be done for a GET method

http://tinyurl.com/5b46ec
0
Active Directory Webinar

We all know we need to protect and secure our privileges, but where to start? Join Experts Exchange and ManageEngine on Tuesday, April 11, 2017 10:00 AM PDT to learn how to track and secure privileged users in Active Directory.

 

Author Comment

by:guochu
ID: 21763384
I need to write my own code to my small application. Now, if I can solve the problem below, then everything would be fine!

For example:
byte data [ ] = new byte [10];
int size = 0;
size = fin.read(data);     //fin is the instance of FileInputStream
...
now the content of data is containing GZIP data, e.g [31, -117, 8, 0, 0, 0, 0, 0, 4, 0]
How can I use GZIP to decompress this array?

Thanks!!!
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 21763554
>>  //fin is the instance of FileInputStream

If you were going to use home-brewed code (not sure why you would since the problems have already been solved for you) then you wouldn't use FileInputStream, you'd use GZIPInputStream
0
 

Author Comment

by:guochu
ID: 21764252
When you start reading the http response message, the first several lines are ASCII text then follows with compressed and chunked data.
For example:
HTTP/1.1 200 OK
Cache-Control: no-cache
Connection: close
...
a
9     
578
ÄWmS"9þ~U÷²s
...
0
fin reads up to the end of ASCII text, then continues to read the first chunked data. the first letter "a" means the first chunked data has 10 bytes -
byte data [ ] = new byte [10];
int size = 0;
size = fin.read(data);   //i.e [31], [-117], [8], [0], [0], [0], [0], [0], [4], [0]
My question is how to decompress this array? How can I decode this chunked data to ASCII text?
If I use GZIPInputStream right at the beginning to read this response message, it won't work at all :(

0
 
LVL 86

Expert Comment

by:CEHJ
ID: 21764286
>>If I use GZIPInputStream right at the beginning to read this response message, it won't work at all :(

It will if you use HttpURLConnection
0
 

Author Comment

by:guochu
ID: 21764472
The response message is already saved in file. We need to extract information out from this file. How can the HttpURLConnection open and read this file?
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 21764721
You just need to open a stream on the file. Try using something like below. If you can post an example file, i'll try it


URL url = new URL("thefile.htm");
HttpURLConnection conn = (HttpURLConnection)url.openConnection();

Open in new window

0
 

Author Comment

by:guochu
ID: 21765205
I have attached an example file with the file extension log. You can change any extension as long as we can extract the data out from the file.
httpMessage.log
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 21766985
OK thanks.

>>The response message is already saved in file

First of all though - why is it that you have this contained in files at all? Since you said:

>> I am writing a personal small web browser by using Java

Web browsers operate on a socket connection to a server
0
 

Author Comment

by:guochu
ID: 21772046
This is for testing the correctness of my application!
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 21772365
Well unfortunately, it will make it operate in a very different way. Unless you create a small web server and write those files literally as the response
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 21772433
(An HttpURLConnection [what you need] expects to operate on a web server, not a file)
0
 

Author Comment

by:guochu
ID: 21772441
Do you mean there is no way we can open this mixed data format file by using java?
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 21772522
Opening it is no problem - it's just that HttpURLConnection is not designed to read files
0
 
LVL 86

Accepted Solution

by:
CEHJ earned 500 total points
ID: 21773729
The following works fine for me, with a proper web server
import java.net.*;
import java.io.*;
import java.util.zip.*;
 
public class GzipWebRead {
    public static void main(String[] args) throws Exception {
	URL url = new URL(args[0]);
	HttpURLConnection conn = (HttpURLConnection)url.openConnection();
	conn.setRequestProperty("Accept-Encoding", "gzip");
	InputStream in = new GZIPInputStream(conn.getInputStream());
	int buf = -1;
	while((buf = in.read()) > -1) {
	    System.out.print((char)buf);
	}
	in.close();
    }
}

Open in new window

0
 

Author Comment

by:guochu
ID: 21783407
Thanks CEHJ...
However, I tried to run your program and didn't work. I am not sure your problem can open a file offline.
I need a method can open and read the file (the one I attached before) offline. Do you have some idea about FilterInputStream? I am still learning how to use this class. I think this maybe the right direction should go for it.
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 21784330
>>I am not sure your problem can open a file offline.

No - i've already said that HttpURLConnection is not designed to read files. If your objective is to be a real web client, i suggest, as i've also already said, that you make a test server that simply writes your files on client (the one i posted) connect
0
 

Author Comment

by:guochu
ID: 21796847
Hello CEHJ,
I have been thinking a couple of days about your method. If you can custom make the http request, then it will be perfect!
-----------------------------------------------------------------------------------------------------------------------------------
For example, I use socket to make connection, I can program the send message whatever I want.
-------------------------------------------------------------------------------------------------------------------------------------
sock = new Socket(url, port);
request = sock.getOutputStream();
response = sock.getInputStream();
request.write(sendMessage.getBytes());
length = response.read(recv);
if(length > 0){
   message = new String (recva);
   System.out.println(message);
}
--------------------------------------------------------------------
The sendMessage is a long string -
sendMessage = GET / HTTP/1.1\r\nHost: www.somesite.com\r\nUser-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.1.11) Gecko/20071220 BonEcho/2.0.0.11\r\nAccept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5\r\n
Accept-Language: en-us,en;q=0.5\r\nAccept-Encoding: gzip,deflate\r\nAccept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7\r\nKeep-Alive: 300\r\nConnection: keep-alive\r\n\r\n

Can you make the same http request (as above) by using your method? If yes, I would like to see how! Please let me know! Thanks!
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 21797692
The problem you have is not in making the request. The code i posted works fine - i tested it with my web server. Your problem is, as i've said more times than i care to remember now, that you're trying to read from files instead of connecting to a web server. If you want to keep testing against files instead of a real web server, then you need to follow my last suggestion
0
 

Author Comment

by:guochu
ID: 21798236
Yes, your code is working perfectly. I have completely changed my program because of your suggestion.

I just want to know a bit more about your method.

My method -
sendMessage = "GET /path/example.html HTTP/1.1\r\n" +
                           "Host: www.somesite.com\r\n" +
                           "User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.1.11) Gecko/20071220 BonEcho/2.0.0.11\r\n" +
                           "Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5\r\n" +
                           "Accept-Language: en-us,en;q=0.5\r\n" +
                           "Accept-Encoding: gzip,deflate\r\n" +
                           "Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7\r\n" +
                           "Keep-Alive: 300\r\n" +
                           "Referer: http://www.originalsite.com/\r\n" +
                           "Connection: keep-alive\r\n\r\n"
 
url = "www.somesite.com";
port = 80;
sock = new Socket(url, port);
request = sock.getOutputStream();
request.write(sendMessage.getBytes());
 
Your method -
URL url = new URL("http://www.somesite.com");
HttpURLConnection conn = (HttpURLConnection)url.openConnection();
conn.setRequestProperty("Accept-Encoding", "gzip,deflate");

Can I use method two to do the same thing like method one?
Method one - I can make the sendMessage headers whatever I want.
Method two - what are the methods for "GET /path/example.html HTTP/1.1", "Referer: http://www.originalsite.com/", etc.,

By the way, can I repeat using setRequestProperty to set the other headers as below?

conn.setRequestProperty("User-Agent", "Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.1.11) Gecko/20071220 BonEcho/2.0.0.11");
conn.setRequestProperty("Accept", "text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5");
conn.setRequestProperty("Accept-Language", "en-us,en;q=0.5");
conn.setRequestProperty("Accept-Encoding", "gzip,deflate");
conn.setRequestProperty("Accept-Charset", "ISO-8859-1,utf-8;q=0.7,*;q=0.7");
conn.setRequestProperty("Keep-Alive", "300");
conn.setRequestProperty("Connection", "keep-alive");

Thanks!!!
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 21798385
>>By the way, can I repeat using setRequestProperty to set the other headers as below?

Should be OK, yes
0

Featured Post

Free Tool: Path Explorer

An intuitive utility to help find the CSS path to UI elements on a webpage. These paths are used frequently in a variety of front-end development and QA automation tasks.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
How do I remove an object from a 3 40
login form jsp example 2 37
SMB share across internet 15 65
Eclipse Help Java EE 5,6,7 Documentation, why not Java EE 8 8 30
Whether you’re a college noob or a soon-to-be pro, these tips are sure to help you in your journey to becoming a programming ninja and stand out from the crowd.
In this post we will learn how to connect and configure Android Device (Smartphone etc.) with Android Studio. After that we will run a simple Hello World Program.
The viewer will learn how to user default arguments when defining functions. This method of defining functions will be contrasted with the non-default-argument of defining functions.
The viewer will learn additional member functions of the vector class. Specifically, the capacity and swap member functions will be introduced.

827 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question