Programming Tutorials

URLConnection sample program in Java

By: Ivan Lim Printer Friendly Format    

URLConnection is a general-purpose class for accessing the attributes of a remote resource. Once you make a connection to a remote server, you can use URLConnection to inspect the properties of the remote object before actually transporting it locally. These attributes are exposed by the HTTP protocol specification and, as such, only make sense for URL objects that are using the HTTP protocol. We'll examine the most useful elements of URLConnection here.

In the following example, we create a URLConnection using the openConnection( ) method of a URL object and then use it to examine the document's properties and content:

// Demonstrate URLConnection.
import java.net.*;
import java.io.*;
import java.util.Date;
class UCDemo
{
public static void main(String args[]) throws Exception {
int c;
URL hp = new URL("http://www.java-samples.com/j2me/");
URLConnection hpCon = hp.openConnection();
System.out.println("Date: " + new Date(hpCon.getDate()));
System.out.println("Content-Type: " +
hpCon.getContentType());
System.out.println("Expires: " + hpCon.getExpiration());
System.out.println("Last-Modified: " +
new Date(hpCon.getLastModified()));
int len = hpCon.getContentLength();
System.out.println("Content-Length: " + len);
if (len > 0) {
System.out.println("=== Content ===");
InputStream input = hpCon.getInputStream();
int i = len;
while (((c = input.read()) != -1) && (—i > 0)) {
System.out.print((char) c);
}
input.close();
} else {
System.out.println("No Content Available");
}
}
}

The program establishes an HTTP connection to http://www.java-samples.com over port 80 
and requests the document /j2me/. We then list out the header values and retrieve the content.
The URL and URLConnection classes are good enough for simple programs that want to connect to HTTP servers to fetch content. For more complex applications, you'll probably find that you are better off studying the specification of the HTTP protocol and implementing your own wrappers.