The JavaTM Plug-in Control Panel enables
you to change the default settings used by the Java Plug-in at startup. All
applets running in an active instance of Java Plug-in use these settings.
Starting the Java Plug-in Control Panel
Start the Java Plug-in Control Panel as follows:
On Windows: From the Windows Control Panel, double-click the Java coffee-cup
icon labeled Java Plug-in to launch the Java Plug-in Control Panel.
On Solaris and Linux: You can run the Control Panel by launching the
ControlPanel executable file. In the Java 2 SDK, this file is located at:
<SDK installation directory>/jre/bin/ControlPanel
It is also located at:
<SDK installation directory>/bin/ControlPanel
For example, if your Java 2 SDK is installed at /usr/j2se, launch
the Control Panel with this command:
/usr/j2se/jre/bin/ControlPanel
In a Java 2 Runtime Environment installation, the file is located at:
<JRE installation directory>/bin/ControlPanel
You can also use Netscape to visit the Control Panel applet page, which was installed
inside the JRE directory as the file ControlPanel.html. In the Java 2
SDK this file is located at:
When you have completed your changes to the Control Panel options, click Apply
to save the changes. Click Reset to cancel your changes and reload the
last values that were entered and applied. Note that this is not the same as
the set of default values that were originally set for Java Plug-in when it
was installed.
Control Panel Help
Help for Java Plug-in is available from any panel in the Control
Panel. Help comes up in its own window in response to pushing the Help
button and looks like this:
Setting Control Panel Options
There are eight sub-panels (tabs) in the Java Control Panel. From six of them
you can set various options. The panels are labeled:
The settings shown for check boxes and radial buttons in each panel below,
with the exception of the Browser panel, are the default (installation)
settings. The check boxes for the Browser panel are determined according
to user selection during installation.
Basic Panel
The Basic panel looks like this:
Use the Basic panel to set the following options:
Show Java Console
Displays the Java Console while running applets. The console displays messages
printed by System.out and System.err objects. It is useful
for debugging problems.
Hide console
The console is running but hidden. This is the default setting (checked).
Do not start console
The console is not started.
Show Java in System Tray (Windows only)
The Show Java in System Tray option indicates to the user that a Java
VM is running; it provides control over the Java Plug-in Control Panel and
Java Console; and it provides information about the Java release. When enabled
and Java Plug-in is started, the coffee-cup logo displays in the system tray.
When Java Plug-in is shutdown, the icon is removed from the system tray. This
option is enabled by default (checked).
Note
If Show Java in System Tray is checked, the icon will show up
in the system tray even if Do not start console is selected.
When Java Plug-in is first started and the mouse is pointed at the icon,
a balloon toll tip will appear saying "Java 2 Standard Edition"
along with a clickable link to http://java.sun.com/getjava. Thereafter, until
Java Plug-in is shut down, when the mouse is pointd at the icon, a text box
will say "Java 2 Standard Edition."
When the system tray icon is left-double-clicked, the Java Plug-in Control
Panel will appear. If it is already open, a second Java Plug-in Control Panel
will appear. When the system tray icon is right-clicked, a popup menu will
appear with following menu items:
Open Control Panel
Open/Hide Console
About Java Technology
Hide Icon
Open Control Panel opens the Java Plug-in Control Panel. If it is
already open, a second Java Plug-in Control Panel will appear.
Open/Hide Console: Open Console opens the Java Console if it
is closed; Hide Console hides the Java Console if it is open.
About Java Technology brings up the About - Java box.
Hide Icon removes the icon from the system tray until the user re-enables
it and Java Plug-in is restarted (i.e., the browser is closed, then reopened
on a page with an applet).
Note:
To re-enable the icon, start the Java Plug-in Control Panel, check
Show Java in System Tray, and press Apply.
Show Exception Dialog Box
Show an exception dialog box when exceptions occur. The default setting is
hide the exception dialog box (unchecked).
Advanced Panel
The Advanced panel looks like this:
Use the Advanced panel to set the following options:
Java Runtime Environment
Enables Java Plug-in to run with any Java 2 JRE or SDK, Standard Edition
v 1.4 installed on your machine. Java Plug-in 1.4 is delivered with a default
JRE. However, you can override the default JRE and use an older or newer version
in the 1.4 family. The Control Panel automatically detects all versions of
the Java 2 SDK or JRE installed on your machine, and it displays in a list
box all versions which you can use. The first item in the list will always
be the Java Plug-in default; the last item will always say Other. If you choose
Other, you must specify the path to the Java 2 JRE or SDK, Standard Edition
v 1.4 that you wish to use. Only advanced users should change this option.
Note
Only advanced users should change this option. Changing the default JRE
is not recommended.
Java Runtime Parameters
You can override the Java Plug-in default startup parameters by specifying
custom options in the Java Runtime Parameters field. The syntax is the
same as used with parameters to the java command line invocation. See
the Java 2 Standard Edition (J2SE) documentation for a full list of command
line options. The URL below is subject to change:
Assertion is disabled in Java Plug-in code by default. Since the effect
of assertion is determined during Java Plug-in startup, changing assertion
settings in the Java Plug-in Control Panel will require a browser restart
in order for the new settings to take effect.
Because Java code in Java Plug-in also has built-in assertion, it is
possible to enable the assertion in Java Plug-in code through the following:
-D[ enableassertions | ea ]:sun.plugin
Tracing and logging support
Tracing is a facility to redirect any output in the Java Console to
a trace file (.plugin<version>.trace).
If you do not want to use the default trace file name:
-Djavaplugin.trace.filename=<tracefilename>
Similar to tracing, logging is a facility to redirect any output in
the Java Console to a log file (.plugin<version>.log)
using the Java Logging API. Logging can be turned on by enabling the
property javaplugin.logging.
-Djavaplugin.logging=true
If you do not want to use the default log file name, enter:
-Djavaplugin.log.filename=<logfilename>
Furthermore, if you do not want to overwrite the trace and log files
each session, you can set the property:
-Djavaplugin.outputfiles.overwrite=false.
If the property is set to false, then trace and log files
will be uniquely named for each session. If the default trace and log
file names are used, then the files would be named as follows
Tracing and logging set through the Control Panel will take effect
when the Plug-in is launched, but changes made through the Control Panel
while a Plug-in is running will have no effect until a restart.
For more information about tracing and logging, see the chapter called
Tracing and Logging.
The <connect-address> can be any string (example:
2502) which is used by the Java Debugger (jdb)
later to connect to the JVM
Default connection timeout
When a connection is made by an applet to a server and the server doesn't
respond properly, the applet may appear to hang and may also cause the
browser to hang because, since by default there is no network connection
timeout.
To avoid this problem, Java Plug-in 1.4 has added a default network
timeout value (2 minutes) for all HTTP connections. You can override
this setting in the Java Runtime Parameters:
-Dsun.net.client.defaultConnectTimeout=<value in milliseconds>
Another networking property that you can set is sun.net.client.defaultReadTimeout.
-Dsun.net.client.defaultReadTimeout=<value in milliseconds>
Note
Java Plug-in does not set sun.net.client.defaultReadTimeout
by default. If you want to set it, do so through the Java Runtime
Parameters as shown above.
These properties specify, respectively, the default connect and read
timeout values for the protocol handlers used by java.net.URLConnection.
The default values set by the protocol handlers is -1,
which means there is no timeout set.
sun.net.client.defaultConnectTimeout specifies the timeout
(in milliseconds) to establish the connection to the host. For example,
for http connections it is the timeout when establishing the connection
to the http server. For ftp connections it is the timeout when establishing
the connection to ftp servers.
sun.net.client.defaultReadTimeout specifies the timeout
(in milliseconds) when reading from an input stream when a connection
is established to a resource.
This panel relates only to Microsoft Windows installations; it
does not appear in other installations. Check any browser for which you want
Java Plug-in to be the default Java runtime, instead of the internal JVM of
that browser. This is to enable APPLET tag support in Internet
Explorer and Netscape 6 via Java Plug-in.
Proxies Panel
The Proxies panel looks like this:
Use the Proxies panel to use the browser default settings or to override the
proxy address and port for the different protocols.
Use browser settings
Check this to use the browser default proxy settings. This is the default
setting (checked).
Proxy information table
You can override the default settings by unchecking the "Use browser
settings" check box, then completing the proxy information table beneath
the check box. You can enter the proxy address and port for each of the supported
protocols: HTTP, Secure (HTTPS), FTP, Gopher, and Socks.
No proxy host
This is a host or list of hosts for which no proxy/proxies are to be used.
No proxy host is usually used for an internal host in an intranet environment.
Automatic proxy configuration URL
This is the URL for the JavaScript file (.js or .pac extension) that contains
the FindProxyForURL function. FindProxyForURL has
the logic to determine the proxy server to use for a connection request.
For additional details about proxy configuration, see the chapter called Proxy
Configuration.
Cache Panel
The Cache panel looks like this:
Note
The cache referred to here is the sticky cache; i.e., the disk
cache created and controlled by Java Plug-in which the browser cannot
overwrite. See Applet Caching.
Enable Caching
Check this to enable caching. This is the default setting (checked). With
applet caching enabled, performance is improved because once an applet is
cached it no longer needs to be downloaded when referenced again.
The Java Plug-in caches files of the following types downloaded via HTTP/HTTPS:
Press this to view the cached files. Another dialog (Java Plug-in Cache
Viewer) will pop up and display the cached files. The Cache Viewer displays
the following information about the files in cache: Name, Type, Size, Expire
Date, Last Modified, Version, and URL. In the Cache Viewer you can also
selectively delete files in the cache. This is an alternative to the Clear
Cache option described below, which deletes all files in the cache.
Clear Cache
Press this to clear all files in the cache. You will be prompted (Erase
all files in ... _cache?) before the files are removed.
Location
You can use this to specify the location of the cache. The default location
of the cache is <user home>/.jpi_cache, where <user
home> is the value of the system property user.home.
Its value depends on the OS.
Size
You can check Unlimited to make the cache unlimited in size; or you can
set the Maximum size of the cache. If the cache size exceeds the specified
limit, the oldest files cached will be removed until the cache size is within
the limit.
Compression
You can set the compression of the JAR cache files between None and High.
While you will save memory by specifying higher compression, performance
will be degraded; best performance will be achieved with no compression.
These are certificates for signed applets that are trusted by the user. The
certificates that appear in the signed applet list are read from the certificate
file jpicerts<version> located in the <user home>/.java
directory.
Secure site
These are certificates for secure sites. The certificates that appear in
the Secure site list are read from the certificate file jpihttpscerts<version>
located in the <user home>/.java directory.
Signer CA
These are certificates of Certificate Authorities (CAs) for signed applets;
they are the ones who issue the certificates to the signers of signed applets.
The certificates that appear in the Signer CA list are read from the certificate
file cacerts, located in the <jre>/lib/security
directory.
Secure site CA
These are certificates of Certificate Authorities (CAs) for secure sites;
they are the ones who issue the certificates for secure sites. The certificates
that appear in the Secure site CA list are read from the certificate file
jssecacerts, located in the <jre>/lib/security
directory
For Signed applet and Secure site certificates, there are four
options: Import, Export, Remove, and Detail. The
user can import, export, remove and view the details of a certificate.
For Signer CA and Secure site CA, there is only one option: Detail.
The user can only view the details of a certificate.
Update Panel (Windows only, 1.4.2_01 and higher releases)
Note
This panel is only available on Windows for 1.4.2_01 and higher releases
and only for users with Administrative privileges.
The Update panel looks like this:
The Update panel, in conjunction with the Java Update Scheduler
(jusched.exe), is used to provide the latest Java updates to the
end user.
Update Panel Options
There are two basic options on the Update tab:
Automatic updateavailable only on Windows XP, 2003, 2000 (SP2 or higher)
and set by default for those operating systems
Manual update
Automatic update is performed on a scheduled basis and it is selected by checking
the Check for Updates Automatically check box.
Manual update is performed by pressing the Update Now button.
If you select automatic update, you can then set the notification via the Notify
Me: drop-down menu, and you can set the update schedule via the Advanced...
button.
With notification, you can chose to be notified before an update is downloaded
and before it is installed; or you can chose to be notified only before an update
is installed (i.e., the download is automatic).
The Advanced... allows you to select the desired frequency for updates:
daily, weekly (default), or montly. For daily updates, you can select the time
of the day for the udpate; for weekly updates, you can select the day of the
week and the time of the day; for montly updates, you can select the day of
the month and the time of the day.
You can do manual updates at any time by presseing the Update Now button.
This allows you to do immediate, unscheduled upates.
Java Update Scheduler
The Java Update Scheduler (jusched.exe) is used for launching
automatic updates when Update Automatically is selected in the Update
tab. jusched.exe runs as a background process that launches the
Update Manager at predefined intervals set by the user through the Advanced
... button of the Update tab. The Update Manager coordinates the update
process.
jusched.exe is launched when the user reboots the computer after
installing the SDK/JRE. It is normally tranparent to the user but can be viewed
in the Processes tab of the Windows Task Manager. Should a user for some reason
not want the scheduler to run, it can be killed via End Process button
of the Processes tab.