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Detect browser type from an AppletTag(s): Applet Environment Javascript interaction


Call a Javascript from the Applet

With LiveConnect, we call a javascript to return the "User-Agent".

To compile, make sure that you have the plugin.jar in the classpath (or Eclipse Build Path). This jar is usually located in [JRE]/lib folder. During runtime, it's already included by the Java plugin so you don't have to worry about that.

The Java class

import java.applet.*;
import java.awt.event.*;
import java.awt.*;
import netscape.javascript.*;

public class GetUserAgent extends Applet
implements ActionListener {

  private static final long serialVersionUID = 1L;

  TextField tf;
  Button b1;
  JSObject win;

  public void init(){
    setLayout(new FlowLayout());
    tf = new TextField(35);
    b1 = new Button("get useragent from javascript");

    b1.addActionListener(this);
    add(tf);add(b1);
  }

  public void actionPerformed(ActionEvent ae) {
    if (ae.getSource() == b1) {
      JSObject win = (JSObject)JSObject.getWindow(this);
      tf.setText((String)win.eval("getUserAgent();"));
    }
  }
}
Don't forget the MAYSCRIPT parameter in the APPLET tag, it's required since the Applet is using the JSObject to interact with the Javascript.
<html>
<head>
<script>
 function getUserAgent() {
   return navigator.userAgent;
 }
</script>
</head><body>
<applet code="GetUserAgent.class" MAYSCRIPT height=100 width=500></Applet>
</body>
</html>
Try it here

You need to parse the returned value to detect browser type. Look at this utility, http://code.google.com/p/user-agent-utils/ or at this code : http://nerds.palmdrive.net/useragent/code.html to get the idea.

Get the value from the server-side

When serving the HTML containing the Applet, you add the User-Agent as parameter for the Applet.

In a JSP/EL

<applet ... >
   <param ... >
   <param name="userAgent" value="${header['user-agent']}" />
</applet>
and in the Applet
String userAgent = getParameter("userAgent");
and parse the returned value...
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Written and compiled by Réal Gagnon ©1998-2014
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