What Runs Where on Athena: Web browser Java Plugin Issues
In order to use the Java plugin in Firefox, you need to select Edit -> Preferences -> Content, and select Enable Java.
We've had problems with Java plugins in the past. A Java plugin is necessary for applets that require more advanced Java features than are supported by the base Java level incorporated in the browser. We have seen situations where the browser will sometimes recognize the plugin but not at other times, for no evident reason (you can check the plugins by typing in a URL about:plugins in Firefox). For a plugin to be active, it should appear in the listing of plugins, and the enabled column on the right should say Yes for all features). We've also seen some applets that work with certain plugin versions but break with other ones.
Firefox Plugin Use
As of this writing, Firefox is set to use Java and a Java plugin that is part of the Athena release, version 1.5.0_16-b02. However, you can reconfigure it to use a different version from one of the Java lockers by setting the MOZ_PLUGIN_PATH_OVERRIDE environment variable as shown below. The path to the right plugin in each locker in Java versions prior to 1.5 usually follows the form:
/afs/athena.mit.edu/software/<Java version locker>/distrib/${ATHENA_SYS}/jre/plugin/${ATHENA_SYS}/ns610-gcc32
For example, the following command typed at the Athena prompt would set it to 1.4.2_05:
setenv MOZ_PLUGIN_PATH_OVERRIDE /afs/athena.mit.edu/software/java_v1.4.2_05/distrib/i386_rhel3/jre/plugin/i386_rhel3/ns610-gcc32
Note that ${ATHENA_SYS} refers to the sysname of the Athena release at the time the locker was created; you may need to look in the directory tree to see what it actually is; in older lockers, for Linux, this may be i386_rh9 or i386_rhel3; in recent lockers it will be i386_deb50.
There is an exception:
For the 1.4.1-01 plugin the correct path is:
/afs/athena.mit.edu/software/java_v1.4.1-01/distrib/i386_rhel3/jre/plugin/i386_rhel3/mozilla
For Java 1.5 and later, use path:
/afs/athena.mit.edu/software/<Java version locker>/distrib/${ATHENA_SYS}/jre/plugin/${ATHENA_SYS}/ns7
Values of <Java version locker> that should work are:
java_v1.4.1-01 (with variant path noted above), java_v1.4.2_03, java_v1.4.2_05, java_v1.5.0_20, java_v1.6.0_07, java_v1.6.0_16
If you put a setenv MOZ_PLUGIN_PATH_OVERRIDE command in your ~/.environment file, this will be set automatically every time you log in.
Please note that setting MOZ_PLUGIN_PATH_OVERRIDE may cause Firefox to lose access to other plugins whose locations are set by a related environment variable, MOZ_PLUGIN_PATH, in the Firefox launch script. If this happens and you also need to use those other plugins, you will need to figure out the paths to their locations, and add those paths to MOZ_PLUGIN_PATH_OVERRIDE in a colon-separated list from the path to the Java plugin.
Note 9/17/09: setting the environment variables above to select different plugins may be currently broken due to a bug. We don't know at this time when this will be fixed.
Setting correct tags for embedded applets that need to run in multiple browsers is tricky; see this Sun page for advice.
Finally, please note that an alternative to viewing applets in a Web browser is to use the appletviewer supplied with the JDK. In this case, you normally load the Web page embedding the applet as a file; also note that the tags enclosing the applet need to be different from the ones used for Web browsers.
Users still having problems with our configurations can send questions or comments to the 3partysw@mit.edu mailing list.
