默认情况下，DozerMapper映射，设置为HashSet会破坏元素的顺序

Question

I have 2 DTOS namely OutputResponse and OutputDTO. The format of the class is as follow:

class OutputDTO{

    private LinkedHashSet<String> items;
}

class OutputResponse{

    private Set<String> items;
}

When I try to use DozerMapper to map these 2 objects, it maps the destination to HashSet instead of LinkedHashSet.

class X{

    DozerBeanMapper mapper;

    mapper.map(OutputDTO.class, OutputResponse.class);

}

In the above scenario, the map() method maps the LinkedHashSet to HashSet which destroys the order of output response. Any suggestions regarding this?

Answer 1

If you want the Set of items in OutputResponse to have some kind of order, you will need to use a different Collection implementation. A Set is unordered by definition. List is ordered, as is LinkedHashSet. By defining the items as a Set, you have defined that there is no specific order, and Dozer has honored that specification by using HashSet, which is also unordered.