README
JavaTM Web Start
Technology
Version 1.4.2
Table of Contents
Introduction
Installation Instructions
Using Java Web Start
Software
Introduction
JavaTM Web Start is a
deployment solution for Java-technology-based applications. It is
the plumbing between the computer and the Internet that allows the
user to launch and manage applications right off the Web. Java Web
Start provides easy, one-click activation of applications, and
guarantees that you are always running the latest version of the
application, eliminating complicated installation or upgrade
procedures.
Distributing software across the Web in the tradition manner
requires the user to find the installer on the Web, download the
installer, locate the installer on the system, and then execute the
installer. Once the installer is executed, it prompts for
installation directories and installation options such as full,
typical, or minimum. This is a time-consuming and complicated task,
and one that must be repeated for each new version of the
software.
By contrast, Web-deployed applications, such as your favorite
HTML-based email client and calendar, auction sites, and so
on, are a breeze to install and use. The Web browser has automated
the entire process. There is no complicated download, setup, and
configuration steps, and you are guaranteed to always be running
the latest version.
Java Web Start technology provides the same benefits to
full-featured applications as described above for HTML-based
applications. Java Web Start technology is an application
deployment solution for the Web. Using a full-featured application
instead of an HTML-based client can have many benefits:
- A highly-interactive user interface, comparable to traditional
applications, such as word processors and spreadsheets.
- Lower bandwidth requirements. An application does not
necessarily have to connect back to the Web server on each click,
and it can cache already-downloaded information. Thus, it can
provide better interactivity on slow connections.
- Support for off-line use.
Or course, you still have to download the application the first
time you use it. An HTML-based application, thus has a
first-time activation cost. Typically, a Web page is brought
up in a matter of seconds. A JavaTM-technology-based application will require
download times in the order of minutes on a typical modem
connection. The Java Web Start caches all downloaded files locally
on the computer. Thus, although the first-time activation cost is
higher for applications than for HTML pages, subsequent launches
will be almost instantaneous because all the required resources are
already available locally.
On each launch, Java Web Start checks the Web server to see if a
new version of the application is available, and if so,
automatically downloads and launches it. Thus, applications are
automatically brought up to date. There is no complicated upgrade
procedure.
Security
Java Web Start is built on top of the Java 2 platform, which
provides a comprehensive security architecture. Applications
launched with Java Web Start will, by default, run in a restricted
environment ("sandbox") with limited access to files and network.
Thus, launching applications using Java Web Start maintains system
security and integrity.
An application can request unrestricted access to your system.
In this case, Java Web Start will display a Security Warning
dialog when the application is launched for the first time. The
security warning will show information about the vendor who
developed the application. If you choose to trust the vendor, then
the application will be launched. The information about the origin
of the application is based on digital code signing.
Installation Instructions
Java Web Start is installed with the SDK/JRE. For
installation instructions, follow the standard installation
instructions for the SDK/JRE you are installing.
Using Java Web Start Software
Java Web Start allows you to launch
Java-technology-based applications directly from the Web. An
application can be launched in three different ways:
- From a Web browser by clicking on a link.
- From Java Web Start's built-in Application Manager, which
tracks recently used applications and provides quick access to your
favorite applications.
- From desktop icons or the Start Menu (Microsoft Windows
only).
Regardless of which way is used, Java Web Start will connect back
to the Web server each time an application is launched to check
whether an updated version of the application is available.
Launching from a Web browser
On the Java Web Start demos page (http://www.oracle.com/technetwork/java/javase/javawebstart/index.html),
there are links to a number of applications that can be launched
with a single click of a mouse. Try launching the different
applications by clicking on the Launch buttons. The Web
browser will launch Java Web Start, which will then download,
cache, and execute the given application. You will notice that the
second time you launch an application, it starts much more quickly
since it is already present locally and does not need to be
downloaded again.
Most of the demos on the page are just downloaded and executed
without any user intervention. These applications run in a
restricted environment in which they are prevented from accessing
the local disk and network, and can be guaranteed not to install
any viruses on your computer.
Some demos require extra privileges, such as access to your
local hard disk. For these applications, a security dialog will pop
up with information about the origin of the application based on
who digitally signed the code. The application will run only if you
decide to trust the vendor.
That is really all there is to using Java Web Start, but how
does it work? The HTML links that launch the applications are, in
fact, standard HTML links. However, instead of pointing to another
Web page, they link to a special configuration file called a JNLP
file. The Web browser examines the file extension and/or the MIME
type of the file, and sees that it belongs to Java Web Start. It
then launches Java Web Start with the downloaded JNLP file as an
argument. Java Web Start proceeds with downloading, caching, and
running the application as directed by the JNLP file.
The Application Manager is a built-in part of the Java Web Start
product. It lets you quickly and easily launch applications that
have previously been launched by Java Web Start. It is a
combination of a History menu and a Start/Programs menu for your
Web deployed Java-technology-based applications. The Application
Manager also allows you to see additional information about the
applications, with links the applications' home pages.
You launch an application from the Application Manager by double
clicking on the application icon or by clicking the launch
button.
Another important feature of the Application Manager is the
Preferences dialog which lets you examine and modify settings used
by Java Web Start. For example, this includes tabs which allow you
to:
- Specify an HTTP Proxy (or tell Java Web Start to use the
default browser settings).
- Clear the cache of downloaded applications.
- Specify the location of the different versions of Java runtime
environments.
- Select whether a Java console is to be displayed.
- View the set of root security certificates.
The Application Manager is launched by either clicking on the
Java Web Start icon on the desktop or in the Start Menu on
Microsoft Windows. On the SolarisTM Operating Environment and Linux, it is
launched by invoking the javaws command in the Java Web
Start installation directory. The Application Manager can also be
launched from a Web browser; see, for example, the demos page
(http://www.oracle.com/technetwork/java/javase/javawebstart/index.html).
Launching from desktop icons and the Start Menu (Microsoft
Windows only)
Java Web Start technology can automatically create shortcuts on the
Microsoft Windows desktop and in the Start Menu for Web deployed
Java-technology-based applications. By default, Java Web Start asks
the second time an application is launched, if a shortcut should be
created. This can be changed using the Preference panel.
Shortcuts can also be added and removed by using the Application
Manager, using the Application/Create Shortcut, and using
Application/Remove Shortcut menu item.
Using Java Web Start Software Behind a Proxy
Server/Firewall
Java Web Start software must be configured with the correct proxy
settings in order to launch applications from outside your
firewall. Java Web Start software will automatically try to detect
the proxy settings from the default browser on your system
(Internet Explorer or NetscapeTM
browsers on Microsoft Windows, and Netscape browsers on the Solaris
Operating Environment and Linux). Java Web Start technology
supports most web proxy auto-configuration scripts. It can detect
proxy settings in almost all environments.
If the proxy setting cannot be automatically detected, then you
will be prompted to specify the proxy settings the first time you
use Java Web Start. Java Web Start will also prompt you for a user
name and password required to access an authenticating proxy
server. This user name and password will be stored for the current
invocation of Java Web Start. However, at the time a newly invoked
Java Virtual Machine, if accessing a secure web site, will prompt
you for the user name and password since this information is stored
within a Java Virtual Machine instance.
You can also use the Java Web Start Preferences panel to view or
edit the proxy configuration. Launch the Application Manager,
either by clicking on the icon on the desktop (Microsoft Windows),
or type ./javaws in the Java Web Start installation
directory (Solaris Operating Environment and Linux), and then
select Edit/Preferences. If you are in an environment where
access to the Web is through a proxy server, you are encouraged to
use the Java Web Start Preferences panel to check that these are
set-up correctly.