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Send a message from an Applet to another Applet on a different pageTag(s): Javascript interaction


FirstApplet encodes the message for SecondApplet in the search (or query) section of SecondApplet.html URL. A simple script in SecondApplet.html decodes the search section and dynamically creates a new page containing the APPLET tag for SecondApplet and a PARAM with the message coming from FirstApplet.

FirstApplet.html 

<HTML><HEAD></HEAD><BODY>
<APPLET CODE="FirstApplet.class" 
        HEIGHT=100 
        WIDTH=300>
</APPLET></BODY></HTML>
FirstApplet.java 
import java.applet.*;    
import java.awt.*;
import java.awt.event.*;
import java.net.*;

public class FirstApplet extends Applet implements
    ActionListener {
 Button b;
 TextField t;
 public void init() {
  add(new Label("Message to 2nd applet :"));
  add(t= new TextField(20));
  add(b = new Button("Load 2nd applet"));
  b.addActionListener(this);
  }

 public void actionPerformed(ActionEvent ae) {
  if (ae.getSource() == b) {
    try {
     getAppletContext().showDocument
       (new URL(getCodeBase(), 
         "SecondApplet.html?" + "message=" 
         + URLEncoder.encode(t.getText())));
     }
    catch (Exception e) {
     e.printStackTrace();
     }
    } 
   }
}
SecondApplet.html 
<HTML><HEAD></HEAD><BODY>
<SCRIPT>
// from Javascript How-to general part 3, 
//    replace all occurrence of token by another
//    in a string.
function replace(s, t, u) {
   i = s.indexOf(t);
   r = "";
   if (i == -1) return s;
   r += s.substring(0,i) + u;
   if ( i + t.length < s.length)
     r += replace(s.substring(i + t.length, s.length), t, u);
   return r;
   }
  
strlen = document.location.search.length
if (strlen > 0) {
   theMessage  = document.location.search
   // strip the "message header"
   theMessage = theMessage.substring(1 + 'message='.length,strlen)
   // replace all '+" by space
   theMessage = replace(theMessage, '+', ' ')
   // replace encoded chars by decoded chars if any
   theMessage = unescape(theMessage)
   html = '<APPLET CODE="SecondApplet.class"'
   html += ' HEIGHT=100'
   html += ' WIDTH=400> '
   html += '<PARAM NAME="Message" VALUE="' + theMessage + '"> '
   html += '</APPLET>'
   document.close()
   document.open()
   document.write(html)
   document.close()
   }
</SCRIPT>
</BODY></HTML>
SecondApplet.java 
import java.applet.*;
import java.awt.*;

public class SecondApplet extends Applet {
 public void init() {
   Label l = new Label("Message from 1st Applet");
   add (l);
   TextField tf = new TextField( 50 );
   add(tf);
   String s = getParameter("Message");
   tf.setText(s);
   }
}
You can try it here!

This method is useful when you need to pass the message to the SecondApplet via PARAM tag. But if you don't need the PARAM tag, take a look at this Java How-to.

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