mapstructlisted

# MapStruct Compile-time mapping. Annotation-driven. Avoids hand-written boilerplate. ## Quick start ```java @Mapper(componentModel = "spring", unmappedTargetPolicy = ReportingPolicy.ERROR, nullValueCheckStrategy = NullValueCheckStrategy.ALWAYS) public interface UserMapper { @Mapping(source = "name", target = "fullName") @Mapping(target = "createdAt", ignore = true) User toEntity(CreateUserRequest req); UserResponse toResponse(User user); @Mapping(target = "id", ignore = true) @BeanMapping(nullValuePropertyMappingStrategy = NullValuePropertyMappingStrategy.IGNORE) void update(UpdateUserRequest req, @MappingTarget User user); } ``` Detailed patterns: `references/mapping-patterns.md`, `references/null-strategies.md`, `references/lombok-interop.md`, `references/anti-patterns.md`. ## Assets - `assets/templates/Mapper.java.tmpl` ## Hard rules - ALWAYS `componentModel = "spring"` for Spring DI. - ALWAYS `unmappedTargetPolicy = ReportingPolicy.ERROR` — catches typos at compile. - USE `nullValueCheckStrategy = NullValueCheckStrategy.ALWAYS` for partial-update mappers. - USE `@MappingTarget` for in-place updates. - DO NOT commit generated impl files (`target/generated-sources/` or `build/generated/`) — gitignore. - USE `@AfterMapping` only for cross-field derivation; keep mappers declarative. ## Lombok interop Add `lombok-mapstruct-binding` to annotation processor classpath — otherwise mapping silently breaks. ## Exit criteria