Deal with Java - Embedding Java into an (old) Web Browser

Install Java to start with. Then proceed with an old school Firefox as follows.

To get Java plug-in to work into firefox you need an older version: v52 ESR (not latest release). AND YOU ALSO NEED TO PREVENT IT FROM UPDATING ITSELF TO ESR 60,

cd ~/opt/
#wget https://download-installer.cdn.mozilla.net/pub/firefox/releases/52.4.1esr/linux-x86_64/en-US/firefox-52.4.1esr.tar.bz2
#tar xjf firefox-52.4.1esr.tar.bz2
wget https://download-installer.cdn.mozilla.net/pub/firefox/releases/52.9.0esr/linux-x86_64/en-US/firefox-52.9.0esr.tar.bz2
#rm -rf firefox
tar xjf firefox-52.9.0esr.tar.bz2
cd firefox/
rm -rf update*
./firefox -no-remote
#--ProfileManager

Also disable updates from the Settings,

Tools > Preferences
Advanced // Update // Never check for updates

Deploy the Java plugin,

cd ~/.mozilla/plugins
#cd /usr/lib/firefox-addons/plugins/
ln -s /usr/lib/jvm/java-8-oracle/jre/lib/amd64/libnpjp2.so

Weaken the crypto requirements

Start menu > Oracle Java 8 plugin control panel
Start menu > Oracle Java 9 plugin control panel

or

jcontrol

or

ControlPanel

then

security > add exceptions e.g. http://localhost:xx (the port number matters)

To get to the Java console of e.g. some old enterprise-class servers, a quick and dirty fix would be,

updatedb
locate java.policy

#cp -pi /usr/lib/jvm/java-8-oracle/jre/lib/security/java.policy /usr/lib/jvm/java-8-oracle/jre/lib/security/java.policy.dist
#vi /usr/lib/jvm/java-8-oracle/jre/lib/security/java.policy

cp -pi /etc/java-8-oracle/security/java.policy /etc/java-8-oracle/security/java.policy.dist
vi /etc/java-8-oracle/security/java.policy

cp -pi /etc/java-8-openjdk/security/java.policy /etc/java-8-openjdk/security/java.policy.dist
vi /etc/java-8-openjdk/security/java.policy

grant {
    permission java.security.AllPermission;
};

Resources

Linux 64-bit installation instructions for Java https://www.java.com/en/download/help/linux_x64_install.xml

Java Downloads for Linux https://www.java.com/en/download/linux_manual.jsp

9 Manual Installation and Registration of Java Plugin for Linux https://docs.oracle.com/javase/8/docs/technotes/guides/install/linux_plugin.html

old java versions

Oracle Java Archive https://www.oracle.com/java/technologies/oracle-java-archive-downloads.html

Java 8 Release Highlights https://java.com/en/download/faq/release_changes.xml

Java 7 Release Highlights https://java.com/en/download/faq/release7_changes.xml

Java SE 7 Archive Downloads https://www.oracle.com/java/technologies/javase/javase7-archive-downloads.html

Java SE 6 Downloads https://www.oracle.com/java/technologies/javase-java-archive-javase6-downloads.html

openjdk + icedtea-plugin

How to install the Java plugin for Firefox? https://askubuntu.com/questions/354361/how-to-install-the-java-plugin-for-firefox/354406