Dynamic API Design - objectives

Objective:

Create a configurable Java framework using Spring Boot that processes API requests based on a product category parameter. The framework should dynamically select processing strategies and handle complex workflows with external service calls.

1. Core Functionality:

• Parse `product_category` from either query parameters or JSON payload
• Select appropriate processing strategy based on category
• Support configurable processing blocks in sequence
• Handle parallel or sequential external service calls
• Collate results and prepare unified response

2. Processing Blocks:

• Input parsing, validation, and transformation
• External service calls with transformers
• Result collection and aggregation
• Response formatting and delivery
• Each block should support custom implementations

3. Design Patterns:

• Strategy: For different product category implementations
• Template Method: In BaseProcessingStrategy for common flow
• Factory: For strategy creation and management
• Builder: For complex objects like contexts and responses
• Visitor/Chain: For validation and transformation chains

4. Technical Requirements:

• Java 17
• Latest Spring Boot
• Configurable via YAML
• Support for retry mechanisms
• Comprehensive exception handling
• Unit and integration testing

5. Configurability:

• Strategy selection
• Processing sequence
• Validation rules
• Transformation logic
• External service configurations
• Retry policies
• Parallel/Sequential execution

6. Package Structure:

- config/           - Configuration classes
- controller/       - API endpoints
- exception/        - Custom exceptions
- factory/          - Strategy factories
- model/            - Data models
- processor/        - Processing components
- service/          - External service clients
- strategy/         - Strategy implementations
- transformer/      - Data transformers
- validator/        - Validation rules

7. Key Components:

• Core Interfaces:

  • ProcessingStrategy
  • InputTransformer
  • ExternalCallTransformer
  • CollationTransformer
  • ValidationRule

• Base Classes:

  • BaseProcessingStrategy
  • BusinessException
  • BaseValidator

• Models:

  • RequestContext
  • ProcessedInput
  • ExternalCallResult
  • CollatedResult
  • ResponseDTO

• Configuration:

  • ProcessingConfig
  • StrategyConfig
  • ExternalCallConfig
  • RetryConfig

8. Error Handling:

• Business exceptions per processing stage
• Validation exceptions
• Transformation exceptions
• External service exceptions
• Global error handling

9. Testing Requirements:

• Unit tests for all components
• Integration tests for full flows
• Mock external services
• Test different configurations
• Performance testing

10. Sample Implementations:

• Category1Strategy (e.g., Order Processing)
• Category2Strategy (e.g., User Profile)
• Corresponding transformers and validators

Output:

The framework should produce a response that includes:

• Processed data
• Success/failure status
• Processing metadata
• Warnings or errors if any
• Execution metrics

This will serve as a foundation for building specific implementations while maintaining flexibility and extensibility.