Mapping list size to int field with modelmapper

Question

I am new to modelmapper. I have Department and Staff classes in my SpringBoot project. Department class has list of staffs. Using ModelMapper I want to create DepartmentDTO that has staffCount field. I have added Department and DepartmentDTO classes below. How to achive this mapping?

Department class

public class Department {

    private Long id;
    private String departmentName;
    private Set<Staff> staffList = new HashSet<>();


    public Department(String departmentName) {
        super();
        this.departmentName = departmentName;
    }

    // getters and setters
} 

DepartmentDTO class

public class DepartmentDTO {

    private Long id;
    private String departmentName;
    private int staffCount = 0;

    public DepartmentDTO(String departmentName) {
        this.departmentName = departmentName;
    }

    // getters and setters

}

Answer 1

I have found solution from this post. I have created DepartmentStaffListToStaffCountConverter class. And used it when adding mappings to modelmapper instance on SpringBootApplication configuration file.

DepartmentStaffListToStaffCountConverter

public class DepartmentStaffListToStaffCountConverter extends AbstractConverter<Set<Staff>, Integer> {

    @Override
    protected Integer convert(Set<Staff> staffList) {
        if(staffList != null) {
            return staffList.size();
        } else {
            return 0;
        }
    }
}

SpringBootApplication file

@SpringBootApplication
public class SpringBootApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringBootApplication.class, args);
    }

    @Bean
    public ModelMapper getModelMapper() {
        ModelMapper modelMapper = new ModelMapper();
        modelMapper.getConfiguration().setMatchingStrategy(MatchingStrategies.STRICT);
        modelMapper.typeMap(Department.class, DepartmentDTO.class)
                   .addMappings(new PropertyMap<Department, DepartmentDTO>() {
            @Override
            protected void configure() {
                using(new DepartmentStaffListToStaffCountConverter()).map(source.getStaffList(), destination.getStaffCount());
            }
        });
        return modelMapper;
    }
}