add full project source-code

Author: cevheri

.gitignore

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+HELP.md
+target/
+!.mvn/wrapper/maven-wrapper.jar
+!**/src/main/**/target/
+!**/src/test/**/target/
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+build/
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### VS Code ###
+.vscode/

.mvn/wrapper/maven-wrapper.properties

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+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+wrapperVersion=3.3.2
+distributionType=only-script
+distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.9.7/apache-maven-3.9.7-bin.zip

Dockerfile

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+# Spring boot application Dockerfile with overridable environment variables
+
+FROM maven:3.9.8-eclipse-temurin-17-focal AS builder
+COPY . /app
+WORKDIR /app
+RUN mvn clean verify
+
+FROM eclipse-temurin:17.0.9_9-jre-focal
+VOLUME /tmp
+WORKDIR /app
+COPY --from=builder /app/target/*.jar /app/app.jar
+ENTRYPOINT [ "java", "-jar", "/app/app.jar" ]
+
+
+# Optional environment variables that can be overriden
+#ENV APP_PROPERTIES_NAME=overriden-application-name
+#ENV APP_ROLES_0=overriden-role-0
+#ENV APP_PATHS_0_ROLES_0=overriden-path-0-role-0

README.md

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+# 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.
+
+## Overview
+1. This guide will show you how to override environment variables in a Spring Boot application.
+2. Single and multiple 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.
+---
+
+## Our Use Case
+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-properties:
+  name: "Spring Boot Overriding Environment Variables"
+  version: "0.0.1"
+  description: "Spring Boot Overriding Environment Variables with application.yml"
+  author: "Cevheri"
+  email: "cevheribozoglan@gmail.com"
+```
+* OS Environment Variable
+```shell
+APP_PROPERTIES_NAME=overridden-name
+APP_PROPERTIES_VERSION=overridden-version
+APP_PROPERTIES_DESCRIPTION=overridden-description
+APP_PROPERTIES_AUTHOR=overridden-author
+APP_PROPERTIES_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-properties.name=overridden-name-cevheri' '-Dapp-roles[0]=overridden-role-0-cevheri' '-Dapp-paths[0].roles[4]=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_PROPERTIES_NAME=overridden-name-cevheri-docker -e APP_ROLES_0=overridden-role-0-cevheri-docker -e APP_PATHS_0_ROLES_4=overridden-path-0-role-0-cevheri-docker soe:latest
+```
+
+
+### 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/