Java plugin not loading in Firefox 21

[Lars Steinke]

Java plugin is missing from about:plugins and plugin list in Firefox Add-ons-Manager, even though it is clearly installed:
# ls -la /usr/lib/mozilla/plugins
...
lrwxrwxrwx 1 root root 39 Mai 20 17:39 libjavaplugin.so -> /etc/alternatives/mozilla-javaplugin.so
...

and

# ls -la /etc/alternatives/mozilla-javaplugin.so
lrwxrwxrwx 1 root root 64 Mai 20 17:39 /etc/alternatives/mozilla-javaplugin.so -> /usr/lib/jvm/java-7-openjdk-amd64/jre/lib/amd64/IcedTeaPlugin.so

PrefBar also complains "No Java Plugin found!" when trying to enable.

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: icedtea-7-plugin 1.3.2-1ubuntu1
ProcVersionSignature: Ubuntu 3.8.0-21.32-generic 3.8.8
Uname: Linux 3.8.0-21-generic x86_64
NonfreeKernelModules: fglrx
ApportVersion: 2.9.2-0ubuntu8
Architecture: amd64
Date: Mon May 20 17:42:33 2013
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: icedtea-web
UpgradeStatus: Upgraded to raring on 2013-04-29 (21 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Nikita V. Youshchenko (yoush-debian)]

I've been observing this issue on Debian system.

After some exploration I found /usr/lib/mozilla/plugins/libjavaplugin.so pointing to non-existing /etc/alternatives/mozilla-javaplugin.so - perhaps left from some random upgrade.

Repointing that to existing /etc/alternatives/iceweasel-javaplugin.so fixed the issue.

I know that Ubuntu uses mozilla corporation's firefox, not debian's rebranded iceweasel, however packaging has much in common and thus reason in ubunto could be similar.

[jalzerio (jalzerio)]

lets try to resolv this as I solved with help of a friend
find at your java folder libnpjp2.so
in my case that was on : /usr/lib/java/lib/i386/libnpjp2.so
create a folded named plugins at /usr/lib/firefox/browser
so as root : cd /usr/lib/firefox/browser/plugins
create a simbolic link to /usr/lib/java/lib/i386/libnpjp2.so at this directory
so again as root: ln -s /usr/lib/java/lib/i386/libnpjp2.so ./libnpjp2.so

I some 15 times after succeed

[jalzerio (jalzerio)]

two lines solutions command ( just adjust it to your correct firefox and java folders correct location )
mkdir /usr/lib/firefox/browser/plugins/
ln -s /usr/lib/java/lib/i386/libnpjp2.so /usr/lib/firefox/browser/plugins/libnpjp2.so

[Lars Steinke (lss)]

Thanks everyone,

but as I described initially, the link to the plugin in /etc/alternatives and from there to /usr/lib/jvm/java-7-openjdk-amd64/jre/lib/amd64 is intact, that plugin is simply NOT loaded - not even if I add it to /usr/lib/firefox/plugins as well:
sudo ln -s /etc/alternatives/mozilla-javaplugin.so /usr/lib/firefox/plugins/libjavaplugin.so

And using the JRE6 plugin libnpjp2.so is probably rather suicidal, with that version no longer receiving security patches...

[negora (negora)]

I also suffered from the same problem when I tried to install by hand the latest versions of Firefox and Java Runtime Environment. I downloaded them from their respective websites and installed them in /usr/local/lib32/ . I followed the typical steps to add the JRE plugín to Firefox, but they didn't worked. However, with Firefox 20 it worked well.

The solution came from Jalzerio's message. It seems that, between versions 20 and 21 of Firefox, Mozilla has changed the plug-in directory location from:

$FIREFOX/plugins/

To:

$FIREFOX/browser/plugins/

I moved the plug-in to the latter and it finally worked.

Thank you Jalzeiro.