How to Use Environment Variables in Spring Boot's application.properties

How can we dynamically configure database connection details in Spring Boot's application.properties using environment variables?

export OPENSHIFT_MYSQL_DB_HOST="jdbc:mysql://localhost"
export OPENSHIFT_MYSQL_DB_PORT="3306"
export OPENSHIFT_MYSQL_DB_USERNAME="root"
export OPENSHIFT_MYSQL_DB_PASSWORD="123asd"

In Spring Boot, you can easily use environment variables to configure your application settings, including database connection properties, by referencing them in the application.properties file. This flexibility is particularly useful in multi-environment setups such as local development, continuous integration (like Jenkins), and production deployments (like OpenShift).

spring.datasource.url=${OPENSHIFT_MYSQL_DB_HOST}:${OPENSHIFT_MYSQL_DB_PORT}/nameofDB
spring.datasource.username=${OPENSHIFT_MYSQL_DB_USERNAME}
spring.datasource.password=${OPENSHIFT_MYSQL_DB_PASSWORD}

Causes

• Static configuration in application.properties can lead to problems when deploying across multiple environments.
• Environment-specific styles can require different database credentials and connection URLs.

Solutions

• Define environment variables in your system or CI/CD environments (e.g., Jenkins and OpenShift).
• Refer to these environment variables in your application.properties file using the correct syntax.

Mistake: Incorrect use of variable syntax in application.properties (e.g., using `sqlURL` instead of the correct variable name).

Solution: Ensure to use the exact names of the environment variables. For example, use `OPENSHIFT_MYSQL_DB_HOST` instead of `sqlURL`.

Mistake: Not exporting the environment variables before launching the application or Jenkins build, causing the application to fail to read them.

Solution: Make sure to export the environment variables in the environment where your application is running.

Mistake: Using quotes around environment variables in the application.properties file.

Solution: Do not include quotes when referencing environment variables in application.properties.