URLReader.java

`URLReader.java`

The URL object can access content from the internet.

01: import java.net.*;
02: import java.io.*;
03: 
04: public class URLReader {
05:     public static void main(String[] args) {
06:         URL url;
07:         String name;
08:         int n, nlines;
09:         if (args.length>0) name = args[0];
10:         else name = "https://johnloomis.org";
11:         if (args.length>1) nlines = Integer.parseInt(args[1]);
12:         else nlines = 5;
13:         System.out.println("Opening: " + name);
14:         try {
15:             url = new URL(name);
16:             BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
17:             System.out.println("\nShowing first few lines:\n");
18:             String inp;
19:             for (n=0; n<nlines; n++) {
20:                 inp = in.readLine();
21:                 if (inp==null) break;
22:                 System.out.println(inp);
23:             }
24:             in.close();
25:         }
26:         catch (MalformedURLException e) {
27:             System.out.println(e);
28:         }
29:         catch (IOException e) {
30:             System.out.println(e);
31:         }
32:     }
33: }

Results

This example triggers an URL exception:

C:\prog\java_web>java URLReader www.udayton.edu
Opening: www.udayton.edu
java.net.MalformedURLException: no protocol: www.udayton.edu

This example works:

C:\prog\java_web>java URLReader http://www.udayton.edu 10
Opening: http://www.udayton.edu

Showing first few lines:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">

<head>
        <title>University of Dayton</title>
        <meta name="ROBOTS" content="INDEX,FOLLOW" />
        <meta name="googlebot" content="INDEX,FOLLOW" />
        <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"
/>
        <meta http-equiv="Content-Language" content="en-us" />

Here we access a Python CGI script:

C:\prog\java_web>java URLReader "https://johnloomis.org/python/tconv.py?value=45&from=F"
Opening: https://johnloomis.org/python/tconv.py?value=45&from=F

Showing first few lines:

<html>
<head><title>Temperature Conversion</title></head>
<body>
<p>
45.0 F equals 7.2 C
</html>

Maintained by John Loomis, updated Wed Feb 20 15:40:59 2008