🚀 MapStruct Practical Guide

A concise guide to MapStruct, a Java framework for efficient object mapping. This guide compares MapStruct with ModelMapper, shows SOLID principles in practice, and highlights key annotations.

📋 Table of Contents

1. Introduction
2. MapStruct vs ModelMapper
3. SOLID Principles
4. Key Annotations
5. Resources

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💡 Introduction

MapStruct generates type-safe mapping code at compile-time, avoiding reflection, and making object mapping fast, reliable, and easy to maintain.

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🔄 MapStruct vs ModelMapper

Feature	MapStruct	ModelMapper
How it works	Compile-time code generation	Runtime reflection to map fields
Performance	High, optimized pre-generated code	Lower, reflection adds runtime overhead
Ease of maintenance	Clear annotations, easy to debug	Flexible but less intuitive, errors at runtime

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⚙️ SOLID Principles

• Single Responsibility Principle (SRP): Each mapper class has a single responsibility — mapping objects.
• Open/Closed Principle (OCP): Mappers can be extended/configured via annotations without changing existing code.
• Dependency Inversion Principle (DIP): @Mapper enables dependency injection, easing testing and extension.

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🔖 Key Annotations

Annotation	Description
@Mapper	Declares a MapStruct mapper interface
@Mapping	Defines mapping rules between source and target fields
@MappingTarget	Updates an existing object instead of creating a new one
@AfterMapping	Defines a post-processing method to run after mapping
@BeforeMapping	Defines a method to execute before mapping
@ValueMapping	Maps values between enums

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📚 Resources

• Official MapStruct Documentation
• Using MapStruct to Simplify Java Object Mapping
• Baeldung MapStruct Guide
• Comparative Guide: MapStruct vs ModelMapper