Specify JDK for tomcat7
Solution 1:
You can try this:
Just press Ctrl+Alt+T on your keyboard to open Terminal. When it opens, run the command below.
gksudo gedit /etc/default/tomcat7
When the file opens, uncomment the line that sets the JAVA_HOME variable.
Save and restart tomcat7 server.
Solution 2:
Tomcat will not actually use your JAVA_HOME environmente variable, but look in some predefined locations and in the JAVA_HOME variable set inside the startup script, as other answers point out. If you don't like messing with the tomcat startup script, you could create a symlink for your preferred java installation, which will be picked up by tomcat.
For example:
ln -s /usr/lib/jvm/java-8-oracle /usr/lib/jvm/default-java
Solution 3:
Open terminal
echo $JAVA_HOME
Copy the result. Then
sudo -H gedit /etc/default/tomcat7
Replace #JAVA_HOME=/usr/lib/jvm/openjdk-6-jdk
with the output you copied from $JAVA_HOME
.