5 Essential Features of Mapstruct | Spring Boot Backend #5.2

In this video I show 5 essential features of Mapstruct with which you can solve almost all the operations with Mapstruct. It handles 5 basic features of Mapstruct to solve the most part of the problems.

The video contains the following topics:
* the mapping with constants;
* the inclusion of the imports in the implementation class;
* the Java expressions;
* the default methods of the interfaces and its usage in the Java expressions;
* the dependency of the fields sequence;
* the @MappingTarget annotation to update existing objects.

[omegasilva]

Good explanation of important features. Thanks!

[moussafall]

Hi, thank you for all. I would like you takk about annotation @BeforeMapping

[quickmaths]

at 3:17 how did you get syntax highlighting etc. for the stuff inside java(...) ? It's all a string for me in IntelliJ Ultimate 2021. Anyone else having this?

[aziubin]

Thanks for the video! I found some new ideas for my project. The complicated area when using mapstruct is nested lists/iterable/collections mappings. Could you please cover this may be in new videos?

[venkatr]

is there a way to map string[] {'one', 'two'} to List<TargetClass> targets?

[zenhsuld]

Great video. how to sum and count child table? (one to many
)

[renaudmaxime]

Merci pour les infos. Ça pourrait être intéressant de montrer comment gérer les références circulaires avec mapstruct (comme dans le cadre des relations bidirectionnelles manyToOne oneToMany)

[ainigma]

Thank you Sergio for your video. I have a small issue when I have bidirectional relationship. I get recursive call.

Assume the following scenario:

Department {
@Fetch(FetchMode.SELECT)
@OneToMany(mappedBy = "departmentId", cascade = Cascade.ALL, orphanRemoval = true, fetch = FetchType.EAGER )
private Set<Employee> employees = new LinkedHashSet<Employee>();
}


Employee {
@ManyToOne
@JoinColumn( name = "DEPARTMENT_ID" )
private Department departmentId;
}


I have created a DepartmentDTO which I would like to return to the client. But I receive a stack overflow. It recursively calls the objects.



These are the 2 mappers I have created:
@Mapper(componentModel = "spring")
public interface DepartmentMapper {

List<DepartmentDTO> departmentList, @Context CycleAvoidingMappingContext cycleAvoidingMappingContext);


DepartmentDTO toDepartmentDto(Department department, @Context CycleAvoidingMappingContext cycleAvoidingMappingContext);

}

@Mapper(componentModel = "spring")
public interface EmployeeMapper {

List<EmployeeDTO> employeeList, @Context CycleAvoidingMappingContext cycleAvoidingMappingContext);


EmployeeDTO toEmployeeDto(Employee employee, @Context CycleAvoidingMappingContext cycleAvoidingMappingContext);

}


public class CycleAvoidingMappingContext {

private final Map<Object, Object> knownInstances = new IdentityHashMap<>();

@BeforeMapping
public <T> T getMappedInstance(Object source, @TargetType Class<T> targetType) {
return targetType.cast( knownInstances.get(source) );
}

@BeforeMapping
public void storeMappedInstance(Object source, @MappingTarget Object target) {
knownInstances.put( source, target );
}

}


Inside the service I call the mapper like this:


List<DepartmentDTO> departmentDtoList = listFromDB, new CycleAvoidingMappingContext() );


I would like to send as a response a list of DepartmentDTO which might contain a list of EmployeeDTOs inside of it. But instead I get an infinite loop and then I get a stack overflow. What am I doing incorrectly?

Thank you in advance!

[dmitrikonnov]

Tanks for the video. MapStruct is getting bigger and stronger as well as its community.
Besides, I don't speak french but I can see, someone has had an issue with recursive calls :D So have I. Using @Context CycleAvoidingMappingContext from someone's github-repo as well as @JsonIgnoreProperties ("field name as in callee class") solved my problem. But obviously there's been no best practice, yet, hasn't there?