Can one write/set a cookie from inside a bowser java applet?
Francois Belfort
from inside a Java applet that runs
inside the browser VM. Is that possible?
Can one write a Java Applet that does this?
fb
William Brogden
wrote:
You will have to use JavaScript - it can read public applet
variables and set a cookie.
Bill
--
www.wbrogden.com
Francois Belfort
> > A friend wants to set a permanent cookie
> > from inside a Java applet that runs
> > inside the browser VM. Is that possible?
> >
> > Can one write a Java Applet that does this?
>
> You will have to use JavaScript - it can read public applet
> variables and set a cookie.
My friend wants to do this from inside the java applet,
without javascript, but in Java itself. Is that possible?
(He also stresses that the cookie should be a session cookie,
not a permanent one)
Thanks!
fb
zoopy
I thought at first that it would not be possible (java.applet.AppletContext allows you to inteface
with the browser, but it doesn't provide a set/get cookie methods)
But 'liveconnect' comes to the rescue. It allows you to interact with the browser's DOM from within
the applet. It's a sort of using JavaScript from within Java.
The class below shows an applet setting and reading a cookie. Also included a HTML doc demonstrating
the applet.
Some points for using and compiling:
1) To be able to use a 'liveconnect' applet, the attribute "MAYSCRIPT" is required in the <applet> tag.
2) To compile you need to include 'plugin.jar' in the classpath; this contains the
netscape.javascript.JSObject class. 'plugin.jar' can be found in the lib directory of your JRE, e.g.
C:\Program Files\Java\j2re1.4.2\lib\plugin.jar
3) It's likely not to work with Microsoft's VM, but only with browsers with Sun's Java plugin.
(tried it successfully with Mozilla and IE6 with the jre1.5b2 plugin)
4) To see what the applet is printing, open the Java console.
5) For a session cookie: if you don't specify an expires=<gmtDate> for the cookie, the browser will
remove the cookie at end of session. If you want to set expiration, you'll need to enhance the
applet's setCookie method
Regards,
Z.
---------File: SGCookie.java --------------
import java.applet.Applet;
import netscape.javascript.JSException;
import netscape.javascript.JSObject;
/**
* Demonstration of setting cookies from within an applet.
* <p>
* To be able to use this applet, the attribute "MAYSCRIPT" is required
* in the applet tag, e.g.
* <pre>
* <applet
* code="SGCookie.class"
* codebase="."
* name="cookieApp"
* MAYSCRIPT
* >
* </applet>
* </pre>
* @author zoopy
* @created Aug 17, 2004
*/
public class SGCookie extends Applet
{
private JSObject window;
private JSObject document;
public void init()
{
// Get a reference to the DOM window and document objects
try
{
window = JSObject.getWindow(this);
System.out.println("init()\twindow=" + window);
document = (JSObject) window.getMember("document");
System.out.println("init()\tdocument=" + document);
}
catch (JSException ex)
{
// We couldn't get reference to either object
ex.printStackTrace();
}
}
public void setCookie(String name, String value)
{
if (document == null)
{
// init() failed to obtain a reference to document object.
System.out.println("Can't set cookie: no document reference");
return;
}
try
{
/*
* should do here checks to ensure name and value don't contain
* invalid characters and name is not an empty string
* ...
*/
String cookieText = name + "=" + value;
System.out.println("Setting document.cookie = \"" + cookieText + '"');
// Set document member "cookie" to cookieText
// Similar to Javascript document.cookie = "name=value";
document.setMember("cookie", cookieText);
// Read document cookies; This might return multiple
// name=value pairs separated by ';' (a document can
// have more than one cookie)
// Similar to Javascript cookies = document.cookie;
Object cookies = document.getMember("cookie");
System.out.println("Got document.cookie = \"" + cookies + '"');
}
catch (JSException ex)
{
// Something went wrong
ex.printStackTrace();
}
}
}
---------------------------------------
---------File: demo.html --------------
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>Set Cookie With Java Applet</title>
</head>
<body>
<h1>Set Cookie With Java Applet</h1>
<form name="myForm">
Cookie
name:<input Type="text" value="foo" name="cookieName">
=
value:<input Type="text" value="bar" name="cookieValue">
<input Type="button" value="Set Cookie"
onClick="document.cookieApp.setCookie(document.myForm.cookieName.value,
document.myForm.cookieValue.value)">
</form>
<!-- The MAYSCRIPT attribute is required in order for the Java methods to be available to the
JavaScript functions. -->
<applet code="SGCookie.class" codebase="." name="cookieApp" NOTMAYSCRIPT>
</applet>
</body>
</html>
---------------------------------------
zoopy
> ---------File: demo.html --------------
> <applet code="SGCookie.class" codebase="." name="cookieApp" NOTMAYSCRIPT>
Change that to
<applet code="SGCookie.class" codebase="." name="cookieApp" MAYSCRIPT>
--
Regards,
Z.
Francois Belfort
That is great! Thank you very much for the code!
The code seems to need enabled javascript in the browser.
is there also a way to do this without javascript?
(or at least, with a browser that is not necessarily set to
javascript enabled, so that it works for any setting?)
francois
zoopy
Don't think it works with Javascript disabled (the code eventually uses the Javascript engine of the
browser), but just give it a try (it's easy to test).
--
Regards,
Z.