Tomcat 8 - context.xml use Environment Variable in Datasource

Question

I have a Tomcat 8 project that uses a datasource (see below)

Answer 1

I finally discovered what I actually needed to do here.... Quite simple in the end.

I passed in a java parameter to Tomcat at runtime as shown below.

I added the following bits to setenv.sh

export PUID=abcd

JAVA_OPTS=-Dpuid=${PUID} 

Then edited my context.xml as shown here

So now my Tomcat installation will read this and be able to use a different path for each different PUID.

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Background: This works because Tomcat will automatically perform variable substition in its configuration files:

Tomcat configuration files are formatted as schemaless XML; elements and attributes are case-sensitive.

Apache Ant-style variable substitution is supported; a system property with the name propname may be used in a configuration file using the syntax ${propname}. All system properties are available including those set using the -D syntax, those automatically made available by the JVM and those configured in the $CATALINA_BASE/conf/catalina.properties file.

Apache Tomcat 9 Configuration Reference - Overview

The part:

JAVA_OPTS=-Dpuid=${PUID}

describe above is necessary because Tomcat will only read Java system properties (which are provided by the JVM), but not environment variables (which are provided by the OS/runtime libraries that the JVM is running on). The parameter -D sets a Java system property from the environment variable of the same name.