How to Use Environment Variables in the Datasource Configuration of Tomcat 8's context.xml

How do I configure Tomcat 8's context.xml to utilize environment variables for my datasource?

Using environment variables in Tomcat 8's context.xml for datasource configuration allows for dynamic database connections that enhance security and flexibility. By setting environment variables, you can avoid hardcoding sensitive information such as database credentials into your configuration files.

<Context>
    <Resource name="jdbc/myDB"
              auth="Container"
              type="javax.sql.DataSource"
              username="${env.DB_USERNAME}"
              password="${env.DB_PASSWORD}"
              driverClassName="com.mysql.cj.jdbc.Driver"
              url="jdbc:mysql://${env.DB_HOST}:${env.DB_PORT}/mydb" />
</Context>

Causes

• A common scenario is deploying applications across different environments (development, testing, production) without modifying the code or configuration files each time.
• Hardcoding sensitive information like database passwords in configuration files makes them less secure and harder to maintain.

Solutions

• Set environment variables in the operating system before starting Tomcat, or define them in the Tomcat configuration files (setenv.sh or setenv.bat).
• In context.xml, reference these environment variables using the appropriate syntax. For example:
• <Resource name="jdbc/myDB" auth="Container" type="javax.sql.DataSource" username="${env.DB_USERNAME}" password="${env.DB_PASSWORD}" driverClassName="com.mysql.cj.jdbc.Driver" url="jdbc:mysql://${env.DB_HOST}:${env.DB_PORT}/mydb"/>

Mistake: Not correctly setting environment variables in the operating system or Tomcat configuration.

Solution: Ensure that environment variables are exported correctly and accessible in the context where Tomcat runs.

Mistake: Failing to reference environment variables correctly in context.xml.

Solution: Double-check the syntax used for referencing environment variables, and ensure that they match the names defined in your operating system.