Messaging Mapper

Overview

Messaging Mapper translates between messaging infrastructure messages and domain objects in the application layer, decoupling domain logic from messaging concerns.

Problem

How do you move data between domain objects and messaging infrastructure without coupling them? Applications work with domain-specific objects while messaging systems use message formats. Direct coupling between these creates maintenance issues and prevents independent evolution.

Solution

Create a Messaging Mapper layer that translates between domain objects and messaging infrastructure messages. The mapper handles serialization, deserialization, and any necessary data transformation, keeping domain objects free from messaging concerns.

Key Characteristics

• Bidirectional Translation: Domain objects ↔ Messages
• Decoupling: Separates domain from messaging concerns
• Format Handling: Manages message serialization
• Type Safety: Preserves domain object types
• Encapsulation: Hides messaging details from domain
• Evolution Support: Domain and message formats evolve independently

When to Use

• Separating domain logic from infrastructure
• Multiple message formats for same domain objects
• Domain-driven design architectures
• Need to evolve domain and messaging independently
• Complex domain objects with simple messages
• Testing domain logic without messaging infrastructure
• Hexagonal or clean architecture implementations

Implementation Considerations

• Mapping Strategy: Automatic vs manual mapping
• Performance: Mapping adds overhead
• Null Handling: Decide how to handle missing values
• Nested Objects: Map complex object graphs
• Collections: Handle lists and arrays appropriately
• Validation: Where to validate data
• Version Compatibility: Handle message format changes

Related Patterns

• Message Translator
• Canonical Data Model
• Domain Model (DDD pattern)
• Data Transfer Object