Java Reference
In-Depth Information
System
.
out
.
println
(
line
);
line
=
reader
.
readLine
();
}
connection
.
disconnect
();
In this example, we instantiate a
URL
instance and then open a connection using the
URL.openConnection()
method. This method returns a generic
URLConnection
type, so we
need to typecast it to an
HttpURLConnection
. Once we have a connection, we set the HTTP
method we are invoking by calling
HttpURLConnection.setMethod()
. We want XML from
the server, so we call the
setRequestProperty()
method to set the
Accept
header. We get
the response code and
Content-Type
by calling
getResponseCode()
and
getCon-
tentType()
, respectively. The
getInputStream()
method allows us to read the content sent
from the server using the Java streaming API. We finish up by calling
disconnect()
.
Sending content to the server via a PUT or POST is a little different. Here's an example of
that:
URL url
=
new
new
URL
(
"http://example.com/customers"
);
HttpURLConnection connection
= (
HttpURLConnection
)
url
.
openConnection
();
connection
.
setDoOutput
(
true
true
);
connection
.
setInstanceFollowRedirects
(
false
false
);
connection
.
setRequestMethod
(
"POST"
);
connection
.
setRequestProperty
(
"Content-Type"
,
"application/xml"
);
OutputStream os
=
connection
.
getOutputStream
();
os
.
write
(
"<customer id='333'/>"
.
getBytes
());
os
.
flush
();
iif
(
connection
.
getResponseCode
() !=
HttpURLConnection
.
HTTP_CREATED
) {
throw
throw new
new
RuntimeException
(
"Failed to create customer"
);
}
System
.
out
.
println
(
"Location: "
+
connection
.
getHeaderField
(
"Location"
));
connection
.
disconnect
();
In this example, we create a customer by using POST. We're expecting a response of 201,
“Created,” as well as a
Location
header in the response that points to the URL of our newly
created customer. We need to call
HttpURLConnection.setDoOutput(true)
. This allows
us to write a body for the request. By default,
HttpURLConnection
will automatically follow
redirects. We want to look at our
Location
header, so we call
setInstanceFollowRedir-
ects(false)
to disable this feature. We then call
setRequestMethod()
to tell the connec-
tion we're making a POST request. The
setRequestProperty()
method is called to set the
Content-Type
of our request. We then get a
java.io.OutputStream
to write out the data
and the
Location
response header by calling
getHeaderField()
. Finally, we call
discon-
nect()
to clean up our connection.
