Create Spring Boot Kotlin Project

Create Spring Boot Kotlin project

Scaffolds a Kotlin Spring Boot application from Spring Initializr, customizes dependencies and local service configuration, and validates the generated project with Gradle tests.

When to invoke

• "Create a Spring Boot Kotlin project."
• "Scaffold a reactive Kotlin Spring Boot service."
• "Generate a Spring Boot Kotlin starter with Redis, PostgreSQL, and MongoDB."
• "Set up a Gradle Kotlin Spring Boot skeleton."

Prerequisites and context

• Java 21 is installed; verify with java -version.
• Docker and Docker Compose are installed if local services are required.
• Customize ${input:projectName:demo-kotlin} before running commands when the user supplies a project name.
• Customize artifactId, packageName, and bootVersion in the Spring Initializr request when the project name, package, or Spring Boot version should differ.

Procedure

1. Check Java with java -version.
2. Download the Spring Initializr archive from https://start.spring.io/starter.zip .
3. Unzip starter.zip into ./${input:projectName:demo-kotlin}.
4. Remove starter.zip after extraction with rm -f starter.zip.
5. Add the extra dependencies and application properties below.
6. Create docker-compose.yaml with Redis, PostgreSQL, and MongoDB services when local backing services are needed.
7. Add generated data directories to .gitignore.
8. Run ./gradlew clean test from the generated project root.

Spring Initializr request

curl https://start.spring.io/starter.zip \
  -d artifactId=${input:projectName:demo-kotlin} \
  -d bootVersion=3.4.5 \
  -d dependencies=configuration-processor,webflux,data-r2dbc,postgresql,data-redis-reactive,data-mongodb-reactive,validation,cache,testcontainers \
  -d javaVersion=21 \
  -d language=kotlin \
  -d packageName=com.example \
  -d packaging=jar \
  -d type=gradle-project-kotlin \
  -o starter.zip
unzip starter.zip -d ./${input:projectName:demo-kotlin}
rm -f starter.zip

Dependency additions

Insert these into build.gradle.kts without duplicating existing entries:

dependencies {
  implementation("org.springdoc:springdoc-openapi-starter-webflux-ui:2.8.6")
  testImplementation("com.tngtech.archunit:archunit-junit5:1.2.1")
}

Use springdoc-openapi-starter-webflux-ui, not springdoc-openapi-starter-webmvc-ui, because the generated project includes webflux.

Application configuration

Add the following application.properties sections and fill secret values through the project's normal secret mechanism rather than committing real passwords:

# SpringDoc configurations
springdoc.swagger-ui.doc-expansion=none
springdoc.swagger-ui.operations-sorter=alpha
springdoc.swagger-ui.tags-sorter=alpha

# Redis configurations
spring.data.redis.host=localhost
spring.data.redis.port=6379
spring.data.redis.password=rootroot

# R2DBC configurations
spring.r2dbc.url=r2dbc:postgresql://localhost:5432/postgres
spring.r2dbc.username=postgres
spring.r2dbc.password=rootroot
spring.sql.init.mode=always
spring.sql.init.platform=postgres
spring.sql.init.continue-on-error=true

# MongoDB configurations
spring.data.mongodb.host=localhost
spring.data.mongodb.port=27017
spring.data.mongodb.authentication-database=admin
spring.data.mongodb.username=root
spring.data.mongodb.password=rootroot
spring.data.mongodb.database=test

Local service profile

Create docker-compose.yaml at the project root when local dependencies are needed.

Add redis_data, postgres_data, and mongo_data directories to .gitignore.

Validation commands

./gradlew clean test
docker-compose up -d
./gradlew spring-boot:run
docker-compose rm -sf

Run the optional Docker and application commands only when the user wants services started locally.

Gotchas

• Do not unzip twice: the original instructions repeated the unzip step; extract starter.zip once, then delete it.
• Do not commit real secrets: use local defaults only for disposable development and replace them for shared environments.
• Do not mix MVC and WebFlux starters: match SpringDoc to WebFlux because webflux is in the generated dependency list.

Spring Initializr anchors

The original download-spring-boot-project-template anchor maps to the Spring Initializr request in this skill. Preserve local service paths exactly: ./redis_data maps to /data, ./postgres_data maps to /var/lib/postgresql/data, and ./mongo_data maps to /data/db. Optional commands are docker-compose up -d, ./gradlew spring-boot:run, and docker-compose rm -sf.

Output template

### Spring Boot Kotlin project result

**Status:** created | instructions only | blocked
**Project:** `${input:projectName:demo-kotlin}`
**Package:** `com.example`

**Generated with**
- Java: `21`
- Spring Boot: `3.4.5`
- Build: `gradle-project-kotlin`
- Dependencies: `configuration-processor,webflux,data-r2dbc,postgresql,data-redis-reactive,data-mongodb-reactive,validation,cache,testcontainers`

**Files changed**
- `build.gradle.kts`: <dependency summary>
- `application.properties`: <configuration summary>
- `docker-compose.yaml`: <services added>
- `.gitignore`: <data directories added>

**Validation**
- `java -version`: pass | fail
- `./gradlew clean test`: pass | fail

Quality gate

• artifactId, packageName, and bootVersion match the user's request or documented defaults.
• starter.zip is removed after extraction.
• build.gradle.kts contains SpringDoc WebFlux UI and ArchUnit dependencies without duplicates.
• Redis, R2DBC, MongoDB, and SpringDoc properties are present.
• docker-compose.yaml defines Redis, PostgreSQL, and MongoDB only when local services are needed.
• redis_data, postgres_data, and mongo_data are ignored by Git.
• ./gradlew clean test was run or the blocker is reported.