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https://github.com/cevheri/java-spring-boot-overriding-environment-variables
This is an example Java Spring Boot Application of overriding the application.yml file with the OS environment variables. Single or Array environment variables can be overridden.
https://github.com/cevheri/java-spring-boot-overriding-environment-variables
application-properties application-yml docker dockerfile environment-variables java spring-boot
Last synced: 10 days ago
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This is an example Java Spring Boot Application of overriding the application.yml file with the OS environment variables. Single or Array environment variables can be overridden.
- Host: GitHub
- URL: https://github.com/cevheri/java-spring-boot-overriding-environment-variables
- Owner: cevheri
- Created: 2024-07-29T14:31:37.000Z (4 months ago)
- Default Branch: main
- Last Pushed: 2024-07-30T16:58:49.000Z (4 months ago)
- Last Synced: 2024-07-31T03:28:35.868Z (4 months ago)
- Topics: application-properties, application-yml, docker, dockerfile, environment-variables, java, spring-boot
- Language: Java
- Homepage:
- Size: 1.05 MB
- Stars: 0
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# Java Spring Boot Overriding Environment Variables Guide
This is an example of overriding the application.yml file with the OS environment variables.
`Single` or `Array` environment variables can be overridden.
We talk about many ways to override environment variables in a Spring Boot application. Not autoconfiguration values :(
---
## Understanding Environment Variables
* Your Spring Boot application has a `application.yml` or `application.properties` file.
* The application properties are converted to environment variables when you run the Spring Boot application.
* The environment variables are key-value pairs that are set in the operating system.
* They are used to configure applications and services.
* Many ways to override environment variables in a Spring Boot application.
---
## Overview
1. This guide will show you how to override environment variables in a Spring Boot application.
2. Single and array environment variables will be overridden.
3. When you run a Spring Boot application, the application properties are converted to environment variables.
4. You can override environment variables using the `-D` flag when java -jar is used.
5. You can override environment variables using the `-e` flag when running a Spring Boot application in a Docker container.
6. You can override environment variables using ConfigMaps and Secrets when running a Spring Boot application in a Kubernetes cluster.
7. You can override environment variables using the `application.yml` file from git repository with spring cloud config server.
----
## Prerequisites
* JDK 17
* Maven 3.9x
* Spring Boot 3x
---
## Getting Started
* Clone the repository
```shell
git clone https://github.com/cevheri/java-spring-boot-overriding-environment-variables.git
```
* Change directory
```shell
cd java-spring-boot-overriding-environment-variables
```
* Run the Spring Boot application
```shell
mvn spring-boot:run
```
---
## Our Use Cases
4 and 5 are the most common use cases for overriding environment variables in a Spring Boot application. Maybe next time we can talk about the Kubernetes and Spring Cloud Config Server use cases.
---
## Environments Naming Convention
When you run a Spring Boot application, the application properties are converted to environment variable like UPPER_CASE with underscores.
* application.yml file
```yml
app-object:
name: "Spring Boot Overriding Environment Variables"
version: "0.0.1"
description: "Spring Boot Overriding Environment Variables with application.yml"
author: "Cevheri"
email: "[email protected]"
```
* OS Environment Variable
```shell
APP_OBJECT_NAME=overridden-name
APP_OBJECT_VERSION=overridden-version
APP_OBJECT_DESCRIPTION=overridden-description
APP_OBJECT_AUTHOR=overridden-author
APP_OBJECT_EMAIL=overridden-email
```
---
## Use Cases
Environment variables are key-value pairs that are set in the operating system.
They are used to configure applications and services.
### java -jar
When you run a Spring Boot application using the `java -jar` command, you can override environment variables using the `-D` flag.
### docker run
When you run a Spring Boot application in a Docker container, you can override environment variables using the `-e` flag.
---
## Build
### Maven Build
```shell
mvn clean install
```
### Build Docker Image
```shell
docker build -t soe:latest .
```
---
## Run
Run the Spring Boot application using the `java -jar` command.
### Java
#### Simple
```shell
java -jar target/soe.jar
```
---
#### Override Environment Variables
```shell
java -jar '-Dapp-object.name=overridden-name-cevheri' '-Dapp-arrays.roles[0]=overridden-role-0-cevheri' '-Dapp-multiple.paths[0].roles[0]=overridden-path-0-role-0-cevheri' target/soe.jar
```
---
### Docker
#### Simple
```shell
docker run -p 8080:8080 soe:latest
```
#### Override Environment Variables
```shell
docker run -p 8080:8080 -e APP_OBJECT_NAME=overridden-name-cevheri-docker -e APP_ARRAYS_ROLES_0=overridden-role-0-cevheri-docker -e APP_MULTIPLE_PATHS_0_ROLES_0=overridden-path-0-role-0-cevheri-docker soe:latest
```
---
## Using Spring Bean
```java
@Configuration
@ConfigurationProperties(prefix = "app-multiple")
public class AppPaths {
private List paths;
public List getPaths() {
return paths;
}
public void setPaths(List paths) {
this.paths = paths;
}
public static class Path {
private String method;
private List roles;
public String getMethod() {
return method;
}
public void setMethod(String method) {
this.method = method;
}
public List getRoles() {
return roles;
}
public void setRoles(List roles) {
this.roles = roles;
}
}
}
```
You should override whole array object like below.
```shell
docker run -p 8080:8080 \
-e APP_MULTIPLE_PATHS_0_METHOD=NEW_POST \
-e APP_MULTIPLE_PATHS_0_ROLES_0=new_create \
-e APP_MULTIPLE_PATHS_0_ROLES_1=new_read \
-e APP_MULTIPLE_PATHS_0_ROLES_2=new_update \
-e APP_MULTIPLE_PATHS_0_ROLES_3=new_delete \
-e APP_MULTIPLE_PATHS_0_ROLES_4=new_admin \
soe:latest
```
---
## Test
```shell
mvn test
```
---
## Conclusion
* This guide showed you how to override environment variables in a Spring Boot application.
* Single and multiple(array) environment variables were overridden.
* When you run a Spring Boot application, the application properties are converted to environment variables.
* You can override environment variables using the `-D` flag when java -jar is used.
* You can override environment variables using the `-e` flag when running a Spring Boot application in a Docker container.
---
### Reference Documentation
For further reference, please consider the following sections:
* https://spring.io/guides/gs/spring-boot
* https://docs.spring.io/spring-boot/reference/features/external-config.html
* https://maven.apache.org/guides/index.html
* https://docs.spring.io/spring-boot/3.3.2/maven-plugin
* https://docs.spring.io/spring-boot/3.3.2/maven-plugin/build-image.html
* https://docs.docker.com/compose/environment-variables/set-environment-variables/