ModelMapper mapping the wrong id

Question

I have an issue while mapping a dto to an entity with nested objects. Basically a "DayEntry" cotains many "SingleEntry" and each "SingleEntry" has a "Category". Here are my entities :

@Entity
public @Data class SingleEntry {

    @Id
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    private Integer id ;
    private float value ;
    private boolean isInEntry= true;
    @ManyToOne
    @JoinColumn(nullable=false)
    private Category category;
    @ManyToOne
    @JoinColumn(nullable=false)
    private DayEntry dayEntry;
}

@Entity
public @Data class Category {

    @Id
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    private Integer id;
    @Column(unique = true)
    private String name;
    private String color ="cc8282";
    @OneToMany(mappedBy = "category")
    //@JsonManagedReference
    private List<SingleEntry> singleEntryList;
}

@Entity
public @Data class DayEntry {

    @Id
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    private Integer id;
    @Column(nullable = false)
    private LocalDate date;
    @OneToMany(mappedBy = "dayEntry", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    private List<SingleEntry> singleEntryList;

}

And this is the Dto i'm using :

public @Data class SingleEntryForCreationDto {

    private float value ;
    private boolean isInEntry;
    private int categoryId;
    private int dayEntryId;
}

I'm trying to create a new "SingleEntity" so that's why i have no "id" in the dto as it's going to be generated, but when i use model mapper :

modelMapper.map(singleEntryForCreationDto, SingleEntry.class)

it maps the "categoryId" to the "id" field of the entity "SingleEntry" like you can see in this example of logs :

********* dto == SingleEntryForCreationDto(value=50.0, isInEntry=false, categoryId=2, dayEntryId=1)

********* mapped dto == SingleEntry(id=2, value=50.0, isInEntry=false, category=Category(id=2, name=null, color=cc8282, singleEntryList=null), dayEntry=DayEntry(id=1, date=null, singleEntryList=null))

I looked at the documentation of Modelmapper and tried to change the NamingConventions and Transormation configuration but it didn't help. I must be missing something and i surely don't understand how Modelmapper really works as i couldn't fix it on my own.

I'd appreciate any help or suggestions.

******EDIT : I still don't understand why it mapped categoryId (SingleEntryForCreationDto) to id (SingleEntry). I resolved it this way for now

modelMapper.typeMap(SingleEntryForCreationDto.class,SingleEntry.class).addMappings(mapper -> mapper.skip(SingleEntry::setId));

Answer 1

I couldn't find why your configuration set the value of SingleEntry's id 2, but I think you'd better use explicit mapping.

You can skip any field in destination with PropertyMap configuration.

Explicit mappings example: no skipping but map() https://github.com/modelmapper/modelmapper/blob/master/examples/src/main/java/org/modelmapper/flattening/example2/FlatteningExample2.java

You can find how to use skip() in 'Skipping Properties' section in this link. http://modelmapper.org/javadoc/org/modelmapper/PropertyMap.html

Answer 2

You need to set Matching Strategies to STRICT http://modelmapper.org/user-manual/configuration/#matching-strategies

    @Bean
    public ModelMapper modelMapper() {
        ModelMapper modelMapper = new ModelMapper();
        modelMapper.getConfiguration()
                .setMatchingStrategy(MatchingStrategies.STRICT);
        return modelMapper;
    }