Java Plug-in Control Panel Help

The following topics are covered in this help:

Overview
Saving Options
Setting Control Panel Options

Overview

The Java 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 will use these settings. The Java Plug-in Developer Guide, mentioned in this document, can be found at (URL subject to change). http://java.sun.com/j2se/1.4/docs/guide/plugin/developer_guide/contents.html

Saving Options

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.

Setting Control Panel Options

There are six panels from which you can set various options within the Java Plug-in Control Panel. These panels are labeled:

Basic
Advanced
Browser
Proxies
Cache
Certificates
Update

Each is described separately below.

Basic

Show Java Console

Displays the Java Console while running applets. The console displays messages printed by System.out and System.err. It is useful for debugging problems.

Hide console

The Java Console is running but hidden. This is the default setting (checked).

Do not start console

The Java Console is not started.

Show Exception Dialog Box

Show an exception dialog box when exceptions occur. The default is to not show the exception dialog box (unchecked).

Advanced

Java Run Time Environment

Enables Java Plug-in to run with any Java 2 JRE or SDK, Standard Edition v 1.3 or 1.4 installed on your machine. Java Plug-in 1.3/1.4 is delivered with a default JRE. However, you can override the default JRE and use an older or newer version. The Control Panel automatically detects all versions of the Java 2 SDK or JRE installed on the machine. In the list box all the versions which you can use are displayed. The first item in the list will always be the default JRE; 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 1.3/1.4.

Note

Only advanced users should change this option. Changing the default JRE is not recommended.

Java Run Time Parameters

Overrides the Java Plug-in default startup parameters by specifying custom options. 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:

http://java.sun.com/j2se/1.4/docs/tooldocs/<platform>/java.html

where <platform> is one of the operating systems: solaris, linux, win32.

Below are some examples of Java runtime parameters.

Enabling and disabling assertion support

To enable assertion support, the following system property must be specified in the Java Runtime Parameters:

-D[ enableassertions | ea ][:<package name>"..." | : <class name> ]

To disable assertion in the Java Plug-in, specify the following in the Java Runtime Parameters:

-D[ disableassertions | da ][:<package name>"..." | : <class name> ]

See Assertion Facility for more details on enabling/disabling assertions. http://java.sun.com/j2se/1.4/docs/guide/lang/assert.html (URL 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).

-Djavaplugin.trace=true -Djavaplugin.trace.option=basic|net|security|ext|liveconnect

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

.plugin<username><date hash code>.trace .plugin<username><date hash code>.log

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 Tracing and Logging in the Java Plug-in Developer Guide.

Debugging applets in Java Plug-in

The following options are used when debugging applets in the Java Plug-in. For more information on this topic see the Debugging Support in the Java Plug-in Developer Guide.

-Djava.compiler=NONE -Xnoagent -Xdebug -Xrunjdwp:transport=dt_shmem,address=<connect-address>,server=y,suspend=n

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 there is no network connection timeout (by default it's set to -1, which means there is no timeout set).

To avoid this problem, Java Plug-in 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.

Networking properties description:

sun.net.client.defaultConnectTimeoutsun.net.client.defaultReadTimeout

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.

For the official description of these networking properties, see http://java.sun.com/j2se/1.4/docs/guide/net/properties.html .

Browser

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

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 in the Java Plug-in Developer Guide.

Cache

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 in the Java Plug-in Developer Guide for more information.

Enable Caching

Check this to enable caching. This 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:

.jar (jar file)
.zip (zip file)
.class (java class file)
.au (audio file)
.wav (audio file)
.jpg (image file)
.gif (image file)

View files in Cache

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.

Certificates

Four types of certificates may be selected:

Signed applet
Secure site
Signer CA
Secure site CA

Signed applet

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 Details. 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: Details. The user can only view the details of a certificate.

Update

In this panel, there is a "Get Java Update" button that allows users to obtain the latest update for the Java Runtime Environment from the Java Update web site. This panel relates only to the Microsoft Windows platform; it does not appear in other platforms (i.e. Solaris/Linux).