Web page retrieval

Web page retrieval

•       To locate and retrieve data from the network is to use the URL class.

Example: Download a Web Page

import java.net.*; import java.io.*;

public class RetrieveWebpage {

public static void main (String[] args) { if (args.length > 0) {

try {

//Open the URL for reading

URL u = new URL(args[0]);

InputStream in = u.openStream( );

//  buffer the input to increase performance

BufferedInputStream bis = new BufferedInputStream(in);

//  chain the InputStream to a Reader

Reader r = new

InputStreamReader(bis); int c;

while ((c = r.read( )) != -1) {

System.out.print((char) c);

}

}

catch (MalformedURLException e) { System.err.println(args[0] + " is not a parseable URL");

}

catch (IOException e) {

System.err.println(e);

}

} // end if

} // end main

} // end RetrieveWebpage

•       The program reads a URL from the command line, opens an InputStream from that URL, chains the resulting InputStream to an InputStreamReader using the default encoding.

•       Then uses InputStreamReader's read ( ) method to read successive characters from the file, each of which is printed on System.out. That is, it prints the raw data located at the URL:

•         If the URL references an HTML file, the program's output is raw HTML.