Does ModelMapper library support collections like ArrayList or HashSet?

Question

This question is not relating with AutoMapper. My question is about ModelMapper in java, however I cannot create new tag for modelmapper as my little reputation. Sorry for confusion.

Anyway, my question is that does modelmapper library support collections like arraylist or hashset? it seems not support collection to collection mapping. Is it true?

score 63 · Answer 1 · edited Aug 04 '16 at 08:46

63

You can also map collections () directly:

    List<Person> persons = getPersons();
    // Define the target type
    java.lang.reflect.Type targetListType = new TypeToken<List<PersonDTO>>() {}.getType();
    List<PersonDTO> personDTOs = mapper.map(persons, targetListType);

Documentation on mapping Generics.

edited Aug 04 '16 at 08:46

real_paul

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answered Jul 29 '13 at 08:41

José

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score 8 · Answer 2 · edited Mar 22 '19 at 15:40

8

Or with Java 8:

List<Target> targetList =
    sourceList
        .stream()
        .map(source -> modelMapper.map(source, Target.class))
        .collect(Collectors.toList());

edited Mar 22 '19 at 15:40

Sterling Archer

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answered Mar 22 '19 at 15:22

Phong Bui

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2

The disadvantage with this is that the modelMapper is not doing all of the mapping from one list to another. By using the TypeToken the mapping from one list to another is all encapsulated in the modelMapper. – Xenson Jun 06 '19 at 20:37
I think this way is more readable and I just simply hate that "{}.getType()" (it will look ugly if you reformat the code). And I said "Or..." though :D – Phong Bui Dec 20 '19 at 10:16
1

I like this solution! – Renato Vasconcellos Jun 05 '20 at 17:52
1

elegant solution – Miroslav Trninic Jul 29 '20 at 10:46

score 5 · Answer 3 · answered Jan 19 '17 at 13:48

You can also avoid the TypeToken stuff if you work with arrays:

  List<PropertyDefinition<?>> list = ngbaFactory.convertStandardDefinitions(props);
  ModelMapper modelMapper = new ModelMapper();
  PropertyDefinitionDto[] asArray = modelMapper.map(list, PropertyDefinitionDto[].class);

score 4 · Answer 4 · answered Jul 25 '12 at 16:55

4

Yes - Collection to Collection mapping is supported. Ex:

static class SList {
    List<Integer> name;
}

static class DList {
    List<String> name;
}

public void shouldMapListToListOfDifferentTypes() {
    SList list = new SList();
    list.name = Arrays.asList(Integer.valueOf(1), Integer.valueOf(2), Integer.valueOf(3));
    DList d = modelMapper.map(list, DList.class);

    assertEquals(d.name, Arrays.asList("1", "2", "3"));
}

answered Jul 25 '12 at 16:55

Jonathan

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For this example you used two wrapper classes around the Collections. Would it be possible without them? – miguelcobain Oct 12 '12 at 18:43
@miguelcobain - Yes, the wrappers just happened to be the example I gave. – Jonathan Nov 05 '12 at 21:44

William · Answer 5 · 2021-04-10T21:24:30.980

1

Even if all the answers are correct in their own way, I would like to share a rather simplified and easy way of doing it. For this example let's supose we have a list of entities from the database and we want to map into his respective DTO.

Collection<YourEntity> ListEntities = //GET LIST SOMEHOW;
Collection<YourDTO> ListDTO = Arrays.asList(modelMapper.map(ListEntities, YourDTO[].class));

You can read more at: https://docs.oracle.com/javase/8/docs/api/java/util/Arrays.html

You can still use a more old school way to do it: https://www.baeldung.com/java-modelmapper-lists

Use with moderation (or not).

edited Apr 10 '21 at 21:24

answered Apr 10 '21 at 20:00

William

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The resultant List will be sorted in what way? Since the target class is provided as an array (YourDTO[]) then converted to a List. Is there a way of knowing how the resultant list will be sorted? – Lewis Munene May 27 '21 at 15:46
@LewisMunene ListDTO should keep the same order as the ListEntities. https://stackoverflow.com/questions/4972406/does-the-list-returned-from-arrays-aslist-maintain-the-same-order-as-the-origina – William May 28 '21 at 12:15

Does ModelMapper library support collections like ArrayList or HashSet?

5 Answers5