Extracting values from a String containing a HTTP header

Question

I'm seeking a better way to extract data from a String that contains a HTTP header. For example, I'd like to get the number 160 from the content length portion of the string: "Content-Length: 160\r\n".

It appears that all the data in the HTTP header is preceded with a name, colon and space, and after the value immediately follows the '\r' and '\n' characters.

At the moment I am doing this:

int contentLengthIndex = serverHeader.lastIndexOf("Content-Length: ");
int contentLastIndex = serverHeader.length()-1;
String contentText = serverHeader.substring(contentLengthIndex + 16, contentLastIndex);
contentText = contentText.replaceAll("(\\r|\\n)", "");
int contentLength = Integer.parseInt(contentText);

But it seems messy and it is only good for getting the "Content-Length" at the end of the string. Is there a better more universal solution for extracting values from a String containing a HTTP header that can be adjusted to work for obtaining both int values or String values?

I should also mention that the connection needs to be able return data back to the browser after a request, which from my understanding prevents me from reaping the benefits of using HttpURLConnection.

@SuKu, I'm storing them character by character into a String. I'm away from the code right now but I believe it's through InputStreamReader. — Ein Doofus
– Ein Doofus, Commented Feb 10, 2013 at 17:14
definitely it has to be some Reader but what is the source of that Reader,I mean you can proceed using HttpURLConnection the way i have mentioned in my answer. — kaysush
– kaysush, Commented Feb 10, 2013 at 17:17
@SuKu, Unfortunately I can't use HttpURLConnection since I'm going to need to use to the connection to send data back to the requesting browser. — Ein Doofus
– Ein Doofus, Commented Feb 10, 2013 at 18:44

iTech · Accepted Answer · 2013-02-10 18:47:39Z

2

A quick solution will be:

new Scanner(serverHeader).useDelimiter("[^\\d]+").nextInt());

The other way if you want to create a Hashtable of the headers:

 String[] fields = serverHeader.trim().split(":");

 String key = fields[0].trim();
 String value = fields[1].trim();

I am not sure why you are doing this manual, there is already API for this!

edited Feb 10, 2013 at 18:47

answered Feb 10, 2013 at 16:44

iTech

18.5k4 gold badges63 silver badges81 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Whymarrh Over a year ago

There seems to be an extra paren.

Ein Doofus Over a year ago

This appears as though it will only works for int values of name/value pairs, and it looks as though it'll only work if the "Content-Length" is known to be 160. I'd like to be able to extract by using the name from the name/value if there is a way.

iTech Over a year ago

I used the hard-coded string only as example, just put your variable there.

Ein Doofus Over a year ago

@iTech, which API are you referring to? I'm new to this so maybe I'm going about it the wrong way.

iTech Over a year ago

For example if you are using servlet you can just call request.getHeader(headerName). The code in your question does not show how you make your connection or if it client or server side

Dumas45 · Accepted Answer · 2013-02-10 19:14:15Z

1

use Class java.net.HttpURLConnection

edited: also methods URLConnection.getContentLength() and URLConnection.getContentLengthLong()

edited Feb 10, 2013 at 19:14

answered Feb 10, 2013 at 16:52

Dumas45

5412 gold badges10 silver badges20 bronze badges

2 Comments

Ein Doofus Over a year ago

I have to be able to use the connection to return data back to the browser after processing the GET request and I don't believe a HttpURLConnection allows for that.

Dumas45 Over a year ago

There are methods URLConnection.getContentLength() and URLConnection.getContentLengthLong() URL url = new URL("yahoo.com/"); URLConnection connection = url.openConnection(); long connectionLength = connection.getContentLengthLong();

Trevor · Accepted Answer · 2013-02-10 16:36:39Z

0

Have you tried just stripping all non-numeric characters from the string?

serverHeader = serverHeader.replaceAll("[^\\d.]", "");

answered Feb 10, 2013 at 16:36

Trevor

1,1471 gold badge20 silver badges33 bronze badges

1 Comment

Ein Doofus Over a year ago

I need to be able to get the value from a name/value pair for String values as well.

kaysush · Accepted Answer · 2013-02-10 17:05:00Z

0

If you are using Socket class to read HTTP data i suggest you to use HttpURLConnection as it provides you convenient method to parse the Header Fields.

It has public Map getHeaderFields() method which you can use to get all the fields.

If you want a guide to start using HttpURLConnection you can see it here.

answered Feb 10, 2013 at 17:05

kaysush

4,8464 gold badges31 silver badges52 bronze badges

2 Comments

Ein Doofus Over a year ago

I started experimenting with that but ran into problems with sending data. I'm essentially writing a basic web server. Does HttpURLConnection allow you to take a HTTP request and use that connection to send a response that includes data such as an HTML or text file?

kaysush Over a year ago

No you can't do that. But take a look here java-samples.com/showtutorial.php?tutorialid=236 . You can use similar method to parse your header.

Collectives™ on Stack Overflow

Extracting values from a String containing a HTTP header

4 Answers 4

5 Comments

2 Comments

1 Comment

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

5 Comments

2 Comments

1 Comment

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related