Java was introduced by Sun Microsystems in 1995 and is
generally understood to be the most popular
general-purpose computing language in use today for
interactive possibilities on the web. Java is a beautiful
programming language, strictly object oriented, expressive
and elegant. It has an always-already cross-platform
orientation that lives up to its slogan "write once - run
anywhere".
Until Microsoft had a falling out with Sun, Java was
bundled with Windows by default and was loaded at start
up. Today Java is a separate download and not loaded for
use by a web browser until called. But once loaded, Java
applications take next to no time to get underway.
Java is independent of platform and can run from anywhere. It is used server side, client side and even used in mobile phones for a vast variety of applications performing complex database manipulation, interactive games and visual.
Web browsers impose the following restrictions on any applet loaded over the network:
An applet cannot load libraries or define native methods.
Java cannot ordinarily read or write files on the host that is executing it.
Java cannot make network connections except to the host that it came from.
Java cannot start any program on the host that is executing it.
Java cannot read certain system properties.
Java is one of the safest languages available and cannot harm computer files.
If Java is disabled then CopySafe Web encrypted images will not be visible to Mac and Linux users. CopySafe Web images for those browsers are displayed in a Java security applet that decrypts the images before they can be displayed on the web page. Without decryption no image can be visible and the image remains secure.
If Java is not installed or not enabled for use in a
web browser, the visitor needs to be redirected for advice
and/or download. JavaScript an be used to detect Java
however the result is not reliable for all web browser
types. Also, version needs to be detected because some
browsers have older versions of Java and version 1.4 or
later is required to view CopySafe Web security applets.
The most reliable detection method for Java version,
one that will run from any web page and work for all web
browser types, is using the Java Version Applet
by Andrew Thompson. Then all you need is the
JavaScript for your page header:
<SCRIPT>
<!--
// edit to suit version and Java download
var minversion = "1.4";
var javadownload = "http://www.java.com";
function showerror()
{
window.alert("Java version " + minversion + " or later is
required to view this page!\n\nIf java is installed it
needs to be enabled.\n\nOr you can get the latest version
from www.java.com");
document.location.href = javadownload;
}
function showJVMDetails()
{
var undefined;
var app = document.applets[0];
var version3 = app.getVersion();
var version = (version3.substr(0,3));
if ((version*1) < (minversion*1))
{
window.alert("Java version " + minversion + " or later is
required to view this page!\n\nYou can get the latest
version from www.java.com");
document.location.href = javadownload;
}
}
window.onerror = showerror;
// -->
</SCRIPT>
Then add an onload statement to your BODY tag and the
applet code just below:
<BODY onload="showJVMDetails();">
<APPLET height="0" width="0" code="JavaVersionDisplayApplet.class"
name="display">
</APPLET>
If your visitor has Java version less than 1.4 they
will be redirected to java.com for download. If they Java
disabled, they will get the hint.
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