Spring Boot read environment variables inside application-properties

Question

So I have been trying to figure out how to use environment-variables in either application.properties or application.yaml. Since this works in countless frameworks (such as Laravel for example), I assumed this would also work in Spring Boot. Now as I have found out, this is not the case.

I saw a post about Spring Environment API, that started that the environment-variable SPRING_DATASOURCE_URL would be equivalent to setting spring.datasource.url inside my application. However, this also didn't work for me.

Is there any quick way that allows using variables that are declared inside a .env file?

I'd like to use it like this inside the application.properties if possible. spring.datasource.url=jdbc:postgresql://${DB_HOST}:${DB_PORT}/${DB_NAME}

It works for environment or any other variables but there is no support for .env files as those aren't exposed as environment variables afaik. — M. Deinum
– M. Deinum, Commented Nov 30, 2020 at 18:40
Do you have an alternative solution for this? For example, I want to run it locally by running with configuration file, but when using it with docker, I want to set the properties via. OS Environment variables. — user12952410
– user12952410, Commented Nov 30, 2020 at 18:42
you can have multiple profiles, set variable values as different for each profile and load them during startup — bRiJeSh
– bRiJeSh, Commented Nov 30, 2020 at 18:43
Exposing regular environemt variables works out-of-the-box. It is only that .env file that isn't supported. A docker environment variable just works. — M. Deinum
– M. Deinum, Commented Nov 30, 2020 at 18:43
So if I want it to work with a pure application.properties file in dev and env-variables in prod, I can just create a appilaction-dev.properties with absolute values and a application-prod.properties that uses the ${VAR_NAME} syntax? — user12952410
– user12952410, Commented Nov 30, 2020 at 18:49

jacky-neo · Accepted Answer · 2020-12-01 06:22:33Z

1

.env is way of Python. If you use spring cloud, you can read env variable from configServer then inject them into application.properties.

add some dependency into pom.xml


        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-config</artifactId>
        </dependency>

define a yml to locate config-server. for example, called myBootstrap.yml

spring:
  cloud:
    config:
      fail-fast: true
      uri: http://[config-server-git]
      name: cc
      profile: config
      label: maste

define a file named cc-config.properties and push it into config-server git. The env variables are written in this properties.
use below way to run application jar

java -jar [your-application-jar] --spring.cloud.bootstrap.location=myBootstrap.yml

edited Dec 1, 2020 at 6:22

answered Dec 1, 2020 at 6:13

jacky-neo

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Roman Vottner · Accepted Answer · 2024-01-31 03:22:26Z

The way I start Java Spring Boot applications from within nvim on an Ubuntu Linux machine in a terminal is by using the trick Dat Tran posted recently:

set -a; . /path/to/.env; set +a; mvn spring-boot:run

set -a; and set +a are thereby built-in shell/bash commands where the -a option is documented as:

Each variable or function that is created or modified is given the export attribute and marked for export to the environment of subsequent commands.

where the +a option basically unsets the -a option and allowing stuff that comes afterwards to access the environment variables created during the -a case. This allows Spring Boot basically to pick up environment variables and replace their placeholders in application.yaml or application.properties files.

If you want to pass additional configuration parameters like adding a debugger or opening certain modules you need to also append the following configuration, as explained i.e. here, to the command string from above:

... -Dspring-boot.run.jvmArguments="--add-opens java.base/java.utils=ALL-UNNAMED -Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=5005"

This will instruct Maven to pass along the configuration options to the Spring app.

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