MapStruct : Java Bean Mapping

Introduction

This blog series will guide you through MapStruct, the annotation-based code generator that eliminates boilerplate mapping code in Java applications. Learn how to efficiently map Java objects, handle complex transformations, integrate with Spring Boot, and follow best practices for maintainable, type-safe object mapping. Whether you're working with DTOs, entities, or complex nested structures, MapStruct provides compile-time code generation for optimal performance and type safety.

A. Getting Started

MapStruct Introduction: Why Manual Mapping Sucks — Pain points of manual DTO mapping and comparison with other solutions.
Your First Mapper: From @Mapper to Perfect DTOs — Creating a basic mapper interface and understanding @Mapping annotations.

B. Basic Mapping

Understanding @Mapping Annotations — Field name conventions and automatic mapping.
Field Mapping and Conventions — Handling different field names and automatic mapping strategies.
Testing Your Generated Mapper — Verifying mapper implementations and ensuring correctness.

C. Advanced Techniques

Custom Methods for Complex Transformations — Handling complex mapping scenarios with custom logic.
Handling Nested Objects — Mapping complex object hierarchies and nested structures.
Type Conversions — Converting between String ↔ Date, enums, and custom types.
Collection Mapping — Mapping Lists, Sets, and Maps efficiently.

D. Spring Boot Integration

Injecting Mappers as Spring Beans — Configuring MapStruct mappers in Spring Boot applications.
Best Practices for Layered Architectures — Organizing mappers in service and controller layers.
Performance Comparison — Comparing MapStruct with reflection-based mappers.
Integration with Lombok — Using MapStruct alongside Lombok for cleaner code.

E. Advanced Features

Using @AfterMapping and @BeforeMapping — Lifecycle hooks for custom mapping logic.
Creating and Using Decorators — Extending mapper functionality with decorators.
Handling Null Values — Graceful null handling strategies in mappers.

F. Best Practices & Troubleshooting

DTO to Entity Mapping Patterns — Common patterns for mapping between layers.
Partial Updates with @BeanMapping — Handling partial updates and ignoreByDefault.
Debugging Mapping Issues — Troubleshooting common mapping problems.
Build-Time Code Generation — Generating mapper implementations at build time.

Prerequisites

Java 8+ knowledge
Basic understanding of POJOs/DTOs
Experience with build tools (Maven/Gradle)
Optional: Spring Boot familiarity

Conclusion

By the end of this series, you'll have mastered MapStruct and be able to efficiently map Java objects with compile-time type safety and optimal performance. You'll understand how to handle simple mappings, complex transformations, nested structures, and integrate MapStruct seamlessly into Spring Boot applications. This knowledge will help you eliminate boilerplate mapping code and build maintainable, type-safe object mapping solutions.