Reading a page header with getHeaderField

[cd-rw]

How can I read the file header of a page using getHeaderField()? I'm new to java and I guess this is a pretty easy thing to do. What I want to do is to read the header "tems" but exactly how should I write my program? Any help would be appreciated.

 

[P3AC3MAK3R]

Hi,

maybe the following code snippet will help you out:

try {
    // Create a URLConnection object for a URL
    URL url = new URL("http://hostname:80");
    URLConnection conn = url.openConnection();

    // List all the response headers from the server.
    // Note: The first call to getHeaderFieldKey() will implicit send
    // the HTTP request to the server.
    for (int i=0; ; i++) {
        String headerName = conn.getHeaderFieldKey(i);
        String headerValue = conn.getHeaderField(i);

        if (headerName == null && headerValue == null) {
            // No more headers
            break;
        }
        if (headerName == null) {
            // The header value contains the server's HTTP version
        }
    }
} catch (Exception e) {
}

Source: http://javaalmanac.com/egs/java.net/GetHeaders.html

 

[cd-rw]

Hi,

maybe the following code snippet will help you out:

try {
    // Create a URLConnection object for a URL
    URL url = new URL("http://hostname:80");
    URLConnection conn = url.openConnection();

    // List all the response headers from the server.
    // Note: The first call to getHeaderFieldKey() will implicit send
    // the HTTP request to the server.
    for (int i=0; ; i++) {
        String headerName = conn.getHeaderFieldKey(i);
        String headerValue = conn.getHeaderField(i);

        if (headerName == null && headerValue == null) {
            // No more headers
            break;
        }
        if (headerName == null) {
            // The header value contains the server's HTTP version
        }
    }
} catch (Exception e) {
}

Source: http://javaalmanac.com/egs/java.net/GetHeaders.html

Ok, thanks for the code. If I wanted to make that a stand alone program how would I go about it? I do have a compilator.

 

[P3AC3MAK3R]

Just create a new class like in the following example:

public class HeaderTest {
    public static void main(String[] args) {

        // add the code from above here

    }
}

btw: it's "compiler" and not "compilator".

Checkout the following tutorial for an introduction to the Java basics:

http://java.sun.com/docs/books/tutorial/reallybigindex.html

 

[Roar]

there is also an english forum on http://www.java-forum.org

 

[cd-rw]

Just create a new class like in the following example:

public class HeaderTest {
    public static void main(String[] args) {

        // add the code from above here

    }
}

btw: it's "compiler" and not "compilator".

Checkout the following tutorial for an introduction to the Java basics:

http://java.sun.com/docs/books/tutorial/reallybigindex.html

Ok, thanks for the help. Unfortunately I'm getting three error messages:

/tmp/21194/HeaderTest.java:6: cannot resolve symbol
symbol  : class URL 
location: class HeaderTest
    URL url = new URL("http://www.tes.com");
    ^
/tmp/21194/HeaderTest.java:6: cannot resolve symbol
symbol  : class URL 
location: class HeaderTest
    URL url = new URL("http://www.tes.com");
                  ^
/tmp/21194/HeaderTest.java:7: cannot resolve symbol
symbol  : class URLConnection 
location: class HeaderTest
    URLConnection conn = url.openConnection();
    ^
3 errors

That's when I'm using this code:

public class HeaderTest {
    public static void main(String[] args) {

        try {
    // Create a URLConnection object for a URL
    URL url = new URL("http://www.mod-x.co.uk/mod_x_LeV_2/M_LeVeL3_od/mod_x_3.php");
    URLConnection conn = url.openConnection();

    // List all the response headers from the server.
    // Note: The first call to getHeaderFieldKey() will implicit send
    // the HTTP request to the server.
    for (int i=0; ; i++) {
        String headerName = conn.getHeaderFieldKey(i);
        String headerValue = conn.getHeaderField(i);

        if (headerName == null && headerValue == null) {
            // No more headers
            break;
        }
        if (headerName == null) {
            // The header value contains the server's HTTP version
        }
    }
} catch (Exception e) {
}

    }
}

there is also an english forum on http://www.java-forum.org

Oops, I missed that.

 

[Roar]

the copmiler can't found these class because you have not imported it, but it's neccessary:

import java.net.URL;
import java.net.URLConnection;

 

[cd-rw]

the copmiler can't found these class because you have not imported it, but it's neccessary:

import java.net.URL;
import java.net.URLConnection;

Ok, that was an easy mistake. Anyway I managed to compile the .java file to a .class file but where do I go from here? Should I put it in a jar file?

 

[Griffin]

If your program is finished, then you can put it in a jar file. So it gets started just by clicking on it. And the .class file can be used for other programs if there are any usefull methods or variables

 

[cd-rw]

If your program is finished, then you can put it in a jar file. So it gets started just by clicking on it. And the .class file can be used for other programs if there are any usefull methods or variables

Could you (or someone else) do me a big favor? Run this code and see what output you get.

This is the class file I get when I compile the code (I had to zip it so the upload site would accept it):
http://upl.silentwhisper.net/uplfolders/upload0/HeaderTest.zip

import java.net.URL;
import java.net.URLConnection;

public class HeaderTest {
    public static void main(String[] args) {

        try {
    // Create a URLConnection object for a URL
    URL url = new URL("http://www.mod-x.co.uk:80");
    URLConnection conn = url.openConnection();

    // List all the response headers from the server.
    // Note: The first call to getHeaderFieldKey() will implicit send
    // the HTTP request to the server.
    for (int i=0; ; i++) {
        String headerName = conn.getHeaderFieldKey(i);
        String headerValue = conn.getHeaderField(i);

        if (headerName == null && headerValue == null) {
            // No more headers
            break;
        }
        if (headerName == null) {
            // The header value contains the server's HTTP version
        }
    }
} catch (Exception e) {
}

    }
}

 

[Griffin]

I copied the code into a file and I also tried to start your file. In both cases the are no errors but also nothing visual happens. Of course not, there is nothing in your code that would do an output.
But you have a for-lopp like this

for (int i=0; ; i++)

don't you need something like that

for (int i=0; i<somethingbigger ; i++)

Othwerwise the loop won't do anything!?!?
Ok, it works! Forget it.
And the loop is done 11 times.

 

[Guest]

I copied the code into a file and I also tried to start your file. In both cases the are no errors but also nothing visual happens. Of course not, there is nothing in your code that would do an output.
But you have a for-lopp like this

for (int i=0; ; i++)

don't you need something like that

for (int i=0; i<somethingbigger ; i++)

Othwerwise the loop won't do anything!?!?
Ok, it works! Forget it.
And the loop is done 11 times.

Did you get it to run? In that case what was the output?

 

[cd-rw]

I copied the code into a file and I also tried to start your file. In both cases the are no errors but also nothing visual happens. Of course not, there is nothing in your code that would do an output.
But you have a for-lopp like this

for (int i=0; ; i++)

don't you need something like that

for (int i=0; i<somethingbigger ; i++)

Othwerwise the loop won't do anything!?!?
Ok, it works! Forget it.
And the loop is done 11 times.

Did you get it to run? In that case what was the output?

That was my posting.

 

[Griffin]

Maybe i haven't wrote it precisely enough.
Both class files worked !!! But there was no output no errors or anything else. So i added a line like this:

System.out.println("Programm Output");

I added the code into the loop. And it appeared 11 times.