ModelMapper return Null in DTO fields while mapping from Entity to DTO

Question

ModelMapper returns null in my DTO fields while mapping from Entity Object to Dto. Anyone please explain why I am getting Null response.

TestEntity

@Data
@Entity
@Table(name="TestEntity")
public class TestEntity {
    @Id
    @Column(name="id")
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;

    @Column(name="test_name")
    private String test_name;
}

TestEntityDto

@Data
public class TestEntityDto {

    private long id;
    private String test_name;
}

TestService

@Service
public class TestService {

    @Autowired
    TestEntityRepo testEntityRepo;

    public TestEntityDto getAllTestList() {
        List<TestEntity> testEntity= testEntityRepo.findAll();
        ModelMapper mapper = new ModelMapper();
        TestEntityDto testEntityDto = mapper.map(TestEntity.class, TestEntityDto.class);

        return  testEntityDto;
    }
}

Actual Result:

{
   "id": 0,
   "test_name": null
}

Expected Result:

{
   "id": 1,
   "test_name": "Test"
}

Answer 1

You are trying to map List<TestEntity> to TestEntityDto which is wrong. Try to map for each TestEntity using ModelMapper and make list of TestEntityDto .

public List<TestEntityDto> getAllTestList() {

    List<TestEntity> testEntity= testEntityRepo.findAll();
    List<TestEntityDto> testEntityDtos = new ArrayList<TestEntityDto>();
    ModelMapper mapper = new ModelMapper();
    mapper.getConfiguration().setMatchingStrategy(MatchingStrategies.STRICT);
    for(TestEntity perTestEntity :testEntity){
        TestEntityDto testEntityDto = mapper.map(perTestEntity , TestEntityDto.class);
         testEntityDtos.add(testEntityDto);
    }
    return  testEntityDtos;

}

Answer 2

You are using private String test_name; in class but in dto there is no field named test_name .

Use private String testName; in TestEntity class.

Or

Use private String test_name; in TestEntityDto class.

Update use STRICT mapping and use testEntity for source.

ModelMapper mapper = new ModelMapper();
mapper.getConfiguration().setMatchingStrategy(MatchingStrategies.STRICT);
TestEntityDto testEntityDto = mapper.map(testEntity, TestEntityDto.class);