How do I find what Java version Tomcat6 is using?

Once you have started tomcat simply run the following command at a terminal prompt:

ps -ef | grep tomcat

This will show the process details and indicate which JVM (by folder location) is running tomcat.

If tomcat did not start up yet , you can use the command \bin\cataline version to check which JVM will the tomcat use when you start tomcat using bin\startup

In fact ,\bin\cataline version just call the main class of org.apache.catalina.util.ServerInfo , which is located inside the \lib\catalina.jar . The org.apache.catalina.util.ServerInfo gets the JVM Version and JVM Vendor by the following commands:

System.out.println("JVM Version: " +System.getProperty("java.runtime.version"));
System.out.println("JVM Vendor: " +System.getProperty("java.vm.vendor")); 

So , if the tomcat is running , you can create a JSP page that call org.apache.catalina.util.ServerInfo or just simply call the above System.getProperty() to get the JVM Version and Vendor . Deploy this JSP to the running tomcat instance and browse to it to see the result.

Alternatively, you should know which port is the running tomcat instance using . So , you can use the OS command to find which process is listening to this port. For example in the window , you can use the command netstat -aon to find out the process ID of a process that is listening to a particular port . Then go to the window task manager to check the full file path of this process ID belongs to. .The java version can then be determined from that file path.