MapStruct for automatic mapping in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is MapStruct in Spring Boot?

MapStruct is a code generator that simplifies mapping between Java objects, especially between DTOs and entities, by generating type-safe mappers at compile time.

beginner

How does MapStruct improve mapping compared to manual mapping?

MapStruct generates mapping code automatically, reducing boilerplate, avoiding runtime errors, and improving performance by doing mapping at compile time instead of reflection.

beginner

What annotation do you use to define a MapStruct mapper interface?

You use the @Mapper annotation on an interface to tell MapStruct to generate the implementation for mapping methods defined inside.

intermediate

How do you get an instance of a MapStruct mapper in your Spring Boot application?

You can add componentModel = "spring" in @Mapper to make MapStruct generate a Spring bean, then inject it with @Autowired or constructor injection.

intermediate

What happens if source and target fields have different names in MapStruct?

You can use @Mapping annotation on the method to specify how fields with different names map to each other, by defining source and target explicitly.

What does MapStruct generate for you?

A Database schema migration scripts

B XML configuration files for mapping

C Runtime reflection-based mappers

D Java code for mapping between objects at compile time

MapStruct generates Java code at compile time to map between objects, avoiding runtime reflection.

Which annotation marks an interface as a MapStruct mapper?

A @Mapper

B @Entity

C @Component

D @Service

The @Mapper annotation tells MapStruct to generate the implementation for the interface.

How do you make a MapStruct mapper a Spring bean?

A Add @Component on the interface

B Add componentModel = "spring" in @Mapper

C Use @Autowired on the interface

D Add @Service on the implementation

Setting componentModel = "spring" in @Mapper makes MapStruct generate a Spring bean.

If source and target fields have different names, how do you map them?

A Use @Mapping annotation with source and target attributes

B MapStruct maps them automatically

C Rename fields manually in both classes

D Use @Autowired to inject mapping

You specify field mappings explicitly with @Mapping(source = ..., target = ...).

What is a main benefit of MapStruct over manual mapping?

A It requires no annotations

B It uses reflection at runtime

C It generates mapping code at compile time for better performance

D It only works with XML files

MapStruct generates code at compile time, improving performance and safety.

Explain how MapStruct helps in mapping between DTOs and entities in Spring Boot.

Think about how MapStruct reduces manual coding and errors.

Describe how you handle mapping fields with different names using MapStruct.

Focus on the annotation that lets you define explicit field mappings.