Java Tips - How to to load a document from a URL on a click of a button

This Java swing tip illustrates a method of loding a a document from a URL on a click of a button.Parameters in HTML code are easy to make. Developer will need to let the user know what the names and possible values are for each parameter to use them properly.


import java.net.*;

import java.util.*;

import javax.swing.*;

import javax.swing.event.*;

import java.awt.*;

import java.applet.AppletContext;



public class SiteSelector extends JApplet {

   private Hashtable sites;

   private Vector siteNames;



   public void init()

   {

      sites = new Hashtable();

      siteNames = new Vector();



      getSitesFromHTMLParameters();



      Container c = getContentPane();

      c.add( new JLabel( "Choose a site to browse" ),

             BorderLayout.NORTH );



      final JList siteChooser = new JList( siteNames );

      siteChooser.addListSelectionListener(

         new ListSelectionListener() {

            public void valueChanged( ListSelectionEvent e )

            {

               Object o = siteChooser.getSelectedValue();

               URL newDocument = (URL) sites.get( o );

               AppletContext browser = getAppletContext();

               browser.showDocument( newDocument );

            }

         }

      );

      c.add( new JScrollPane( siteChooser ),

             BorderLayout.CENTER );

   }



   private void getSitesFromHTMLParameters()

   {

      // look for applet parameters in the HTML document

      // and add sites to Hashtable

      String title, location;

      URL url;

      int counter = 0;



      while ( true ) {

         title = getParameter( "title" + counter );



         if ( title != null ) {

            location = getParameter( "location" + counter );

            

            try {

               url = new URL( location );

               sites.put( title, url );

               siteNames.addElement( title );

            }

            catch ( MalformedURLException e ) {

               e.printStackTrace();

            }

         }

         else

            break;



         ++counter;  

      }

   }

}

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