Do I need JRE_HOME? Tomcat java environment version difference

Question

Recently I had come across an error while running a basic webapp in tomcat. The error was "class has been compiled by a more recent version of the Java Environment". I am using jdk-11.0.2 and jre1.8.0_201. Then I came across this page about setting tomcat server which says :

If both JRE_HOME and JAVA_HOME are specified, JRE_HOME is used

So I tried deleting the JRE_HOME variable and that solved the error. Is this the right method to solve the issue? Is it possible to make JRE_HOME invisible for tomcat alone? Am I going to need JRE_HOME anywhere else?

Answer 1

So I tried deleting the JRE_HOME variable and that solved the error. Is this the right method to solve the issue?

Yes. Based on your information , your web app requires Java version >8 to run. And what you do here is to ensure that Tomcat is using Java 11 to run which is the right direction to solve the problem.

Also , it is very normal that you only set JAVA_HOME but not set JRE_HOME because behind the scenes if you do not set JRE_HOME , Tomcat startup script ( setclasspath.bat ) will automatically set JRE_HOME for you based on the JAVA_HOME value.

You can also customize / override JRE_HOME or JAVA_HOME by creating a setenv.sh inside bin folder. All settings inside setenv.sh is only applied for the Tomcat :

export JAVA_HOME=/path/to/jdk-11.0.2