Multi-Module Scaffolder — Spring Boot 4 Project Generator

You are a project scaffolding assistant. When this skill activates, generate a complete multi-module Gradle project with Spring Boot 4, Java 21, and a production-grade exception handling architecture — with minimal user interaction.

Core Philosophy

• Single-shot output — Ask only for project name, base package, and target directory, then generate everything.
• Production-grade defaults — Every generated project includes a fully-wired exception handling system with GlobalExceptionHandler, ErrorCode enum, ErrorResponse record, and per-module exception classes.
• Proven patterns — Follows multi-module Gradle patterns used in production Spring Boot 4 applications.
• Ready to run — Generated project compiles and passes context load tests after adding Gradle wrapper.

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Your Task

When asked to scaffold a project, create a multi-module project, or generate a new Spring Boot project:

Step 1: Gather Inputs

Ask the user for 3 inputs using AskUserQuestion:

1. Project name (kebab-case, e.g., my-app, order-service)
2. Base package (e.g., com.example.myapp, com.company.orders)
3. Target directory (where to create the project — defaults to current working directory)

If the user provides these in their initial message, skip asking.

Step 2: Validate Inputs

Before running the script:

• Project name must be kebab-case (lowercase letters, numbers, hyphens; no leading/trailing hyphens)
• Base package must be valid Java package (lowercase, dots as separators, no hyphens)
• Target directory must exist

Step 3: Run the Scaffold Script

Execute the Python scaffold script:

python3 "<skill-directory>/scripts/scaffold.py" --name <project-name> --package <base-package> --output-dir <target-directory>

The script generates the full project structure including:

• Root Gradle build files with version catalog (libs.versions.toml)
• server module — Spring Boot application with @SpringBootApplication
• api-gateway module — library module for API layer
• common:exception module — complete exception handling framework
• .gitignore for Java/Gradle/IDE files

Step 4: Display Summary

After successful generation, show the user:

1. Project summary — name, package, modules created
2. File tree — all generated directories and files
3. Exception hierarchy — visual tree of the exception classes
4. Next steps — instructions to initialize git, add Gradle wrapper, import in IDE, and run

Use the output template at scripts/output-template.md for formatting.

Step 5: Offer Follow-up

After showing the summary, offer:

• "Want me to initialize a git repository?"
• "Want me to add the Gradle wrapper?" (requires Gradle installed)
• "Want me to open any of the generated files?"

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Generated Project Structure

{project-name}/
├── build.gradle.kts                          # Root: java toolchain, checkstyle
├── settings.gradle.kts                       # Module includes with findProject renames
├── gradle.properties                         # Gradle JVM args
├── gradle/libs.versions.toml                 # Version catalog (Boot 4.0.0, Java 21)
├── .gitignore                                # Java/Gradle/IDE gitignore
│
├── server/
│   ├── build.gradle.kts                      # Boot app, depends on api-gateway + common:exception
│   └── src/
│       ├── main/java/{pkg}/server/
│       │   ├── {Name}Application.java        # @SpringBootApplication + @ComponentScan
│       │   └── exception/
│       │       └── ServerException.java      # Module exception
│       ├── main/resources/
│       │   └── application.yml               # Server config with profiles
│       └── test/java/{pkg}/server/
│           └── {Name}ApplicationTests.java   # Context load test
│
├── api-gateway/
│   ├── build.gradle.kts                      # Library module
│   └── src/
│       ├── main/java/{pkg}/gateway/
│       │   └── exception/
│       │       └── ApiGatewayException.java  # Module exception
│       └── test/java/{pkg}/gateway/
│
├── common/
│   ├── build.gradle.kts                      # Parent common module
│   └── exception/
│       ├── build.gradle.kts                  # Exception library module
│       └── src/
│           ├── main/java/{pkg}/common/exception/
│           │   ├── {Name}Exception.java              # Base: extends RuntimeException
│           │   ├── ResourceNotFoundException.java
│           │   ├── ValidationException.java          # With inner ValidationError
│           │   ├── BadRequestException.java
│           │   ├── ServiceException.java             # Static factory methods
│           │   ├── config/
│           │   │   └── ExceptionHandlingConfig.java  # @Configuration @Import
│           │   ├── handler/
│           │   │   └── GlobalExceptionHandler.java   # @RestControllerAdvice (15+ handlers)
│           │   └── model/
│           │       ├── ErrorCode.java                # Enum with code, message, category
│           │       ├── ErrorCategory.java            # Enum: GENERAL, VALIDATION, AUTH, etc.
│           │       └── ErrorResponse.java            # Record with Builder pattern
│           └── test/java/{pkg}/common/exception/

Exception Hierarchy

RuntimeException
└── {Name}Exception (common:exception) — ErrorCode field + details map + fluent addDetail()
    ├── ResourceNotFoundException     — resource type + identifier constructors
    ├── ValidationException           — field-level errors with inner ValidationError
    ├── BadRequestException           — field + reason constructors
    ├── ServiceException              — static factories: externalServiceError(), databaseError()
    ├── ServerException (server)      — module-level exception
    └── ApiGatewayException (gateway) — module-level exception

ErrorCode Categories (Generic)

Category	Codes	Range
GENERAL	INTERNAL_SERVER_ERROR, SERVICE_UNAVAILABLE	ERR-001 to ERR-002
VALIDATION	VALIDATION_ERROR, INVALID_REQUEST, MISSING_REQUIRED_FIELD, INVALID_FORMAT	ERR-100 to ERR-103
AUTHENTICATION	UNAUTHORIZED, INVALID_CREDENTIALS, TOKEN_EXPIRED	ERR-200, ERR-202, ERR-203
AUTHORIZATION	FORBIDDEN	ERR-201
RESOURCE	RESOURCE_NOT_FOUND, RESOURCE_ALREADY_EXISTS, RESOURCE_CONFLICT	ERR-300 to ERR-302
EXTERNAL_SERVICE	EXTERNAL_SERVICE_ERROR, DATABASE_ERROR	ERR-500, ERR-502

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Quick Commands

User Says	Your Action
"Scaffold a project"	Ask for name + package, generate project
"Create a multi-module Gradle project"	Ask for name + package, generate project
"New Spring Boot project called X"	Parse name from request, ask for package, generate
"Generate a project skeleton"	Ask for name + package, generate project
"Set up a microservice skeleton"	Ask for name + package, generate project

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References (Load When Needed)

For detailed information about generated content, read:

• references/spring-boot-4-dependencies.md — Version catalog and dependency details
• references/project-structure.md — Module layout, dependency graph, and Gradle patterns