Java Reference
In-Depth Information
Do not assume the value returned by
getHeaderField()
is valid. You must check to
make sure it is nonnull.
public String getHeaderFieldKey(int n)
This method returns the key (i.e., the field name) of the
n
th
header field (e.g.,
Content-
length
or
Server
). The request method is header zero and has a null key. The first
header is one. For example, in order to get the sixth key of the header of the
URLConnec
tion
uc
, you would write:
String
header6
=
uc
.
getHeaderFieldKey
(
6
);
public String getHeaderField(int n)
This method returns the value of the
n
th
header field. In HTTP, the starter line containing
the request method and path is header field zero and the first actual header is one.
Example 7-5
uses this method in conjunction with
getHeaderFieldKey()
to print the
entire HTTP header.
Example 7-5. Print the entire HTTP header
import
java.io.*
;
import
java.net.*
;
public
class
AllHeaders
{
public
static
void
main
(
String
[]
args
)
{
for
(
int
i
=
0
;
i
<
args
.
length
;
i
++)
{
try
{
URL
u
=
new
URL
(
args
[
i
]);
URLConnection
uc
=
u
.
openConnection
();
for
(
int
j
=
1
;
;
j
++)
{
String
header
=
uc
.
getHeaderField
(
j
);
if
(
header
==
null
)
break
;
System
.
out
.
println
(
uc
.
getHeaderFieldKey
(
j
)
+
": "
+
header
);
}
}
catch
(
MalformedURLException
ex
)
{
System
.
err
.
println
(
args
[
i
]
+
" is not a URL I understand."
);
}
catch
(
IOException
ex
)
{
System
.
err
.
println
(
ex
);
}
System
.
out
.
println
();
}
}
}
For example, here's the output when this program is run against
http://www.oreilly.com
:
%
java AllHeaders http://www.oreilly.com
Date: Sat, 04 May 2013 11:28:26 GMT
Server: Apache
Last-Modified: Sat, 04 May 2013 07:35:04 GMT
