Using env variables with Spring Boot

This is an example application which demonstrates how to configure a Spring Boot app via environment variables. It expects to receive three properties. Default values are provided in the app.

SPRING_APPLICATION_JSON

You can set a a set of environment variables by assigning a JSON structure to SPRING_APPLICATION_JSON environment variable. For example, to set ec2.public.url to http://mydomain.com, you could run this application as follows.

SPRING_APPLICATION_JSON='{"ec2":{"public":{"url":"http://mydomain.com"}}}'
java -jar configuration-0.0.1-SNAPSHOT.jar

Spring will read SPRING_APPLICATION_JSON environment variable to get its application properties. On application startup, the value of ec2.public.url is printed to the console.

Injecting env variables directly

@Value annotation can be used to inject properties to beans. It also looks for values from the environment. This example demonstrates how the application reads a database url from the environment.

@Value("${DB_URL}")
private String dbUrl;

Run the application as follows.

DB_URL="jdbc:hsqldb:mem:mymemdb"
java -jar configuration-0.0.1-SNAPSHOT.jar

You should see that the database url is printed to the console.

Setting applicaiton.properties values from environment

Similar to the previous approach, it is possible to assign values to properties from the environment in your application.properties file.

api.key=${API_KEY:not set}

And run your app as follows.

API_KEY="123abc"
java -jar configuration-0.0.1-SNAPSHOT.jar