Spring properties env and aliasing

This is a short article about spring properties and how you can alias them and override them via environment variables.

First things first.

• Create a bean to display the properties
• In here I am using Project Lombok to generate code such as slf4j loggers. 
• Make sure the class is @Component or @Service
• @Autowire Environment and ServerProperties
• Create Post Construct method - at least for this purpose, we'll use this method to print variables.
  • In this method you are attempting to read a property from the environment and your aliased property.

package com.scrap;

import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.web.ServerProperties;
import org.springframework.core.env.Environment;
import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;

@Slf4j
@Component
public class ShowProperties {
    @Autowired
    private Environment environment;

    @Autowired
    private ServerProperties serverProperties;



    @PostConstruct
    public void postsConfigure() {
       log.info(environment.getProperty("USERNAME"));
       log.info("compression {}", serverProperties.getCompression().getEnabled());
    }
}

Aliasing the property

In application.properties add the variable you'd like to access; in this case we are using server.compression.enabled; although the variable won't be used for anything other than printing.

Alias the name using the following syntax ${aliasName: defaultValue}

server.compression.enabled=${compression: false}

Export the variable via Environment Variables

export COMPRESSION=true
export USERNAME=Bob

Run Spring

Via Maven

mvn spring-boot:run

Via Java

java -jar YourProject.jar

Output

2018-09-15 13:56:43.822  INFO 89653 --- [main] com.scrap.ShowProperties : compression true
2018-09-15 13:56:43.822  INFO 89653 --- [main] com.scrap.ShowProperties : Bob

...Long environment variables are still resolved

If you'd like to continue using the long name. You can.

export SERVER_COMPRESSION_ENABLED=true

/.

() -> loger.info("/.Springzen");