MapStruct: Mapping 2 objects to a 3rd one

问题

I have Object1 and Object2. Now, I want to map object3, with attributes from 1 & 2.

Say, I have 2 object:

1. User: {first_name, last_name, id}
2. Address: {street, locality, city, state, pin, id}

Now, with these, I want to map that in

User_View: {firstName, lastName, city, state}.

Where, first_name & last_name will be from User object and city & state from Address object.

Now, my question is, how to do that?

However, currently, I'm doing like this

@Mapper    
public abstract class UserViewMapper {
        @Mappings({
                    @Mapping(source = "first_name", target = "firstName"),
                    @Mapping(source = "last_name", target = "lastName"),
                    @Mapping(target = "city", ignore = true),
                    @Mapping(target = "state", ignore = true)

            })
            public abstract UserView userToView(User user);

        public UserView addressToView(UserView userView, Address address) {

                if (userView == null) {
                    return null;
                }

                if (address == null) {
                    return null;
                }

                userView.setCity(address.getCity());
                userView.setState(address.getState()); 

            return userView;

            }
    }

But, here, I have to manually write the mapping in addressToView().

Therefore, is there, any way, to avoid that?

Or, what would be the preferred way, to handle such situations?

回答1:

You can declare a mapping method with several source parameters and refer to the properties of all these parameters in your @Mapping annotations:

@Mapper
public abstract class UserViewMapper {

    @Mapping(source = "first_name", target = "user.firstName"),
    @Mapping(source = "last_name", target = "user.lastName"),
    public abstract UserView userAndAddressToView(User user, Address address);
}

As the "city" and "state" property names match in source and target, there is no need for mapping them.

Also see the chapter "Defining a mapper" in the reference documentation for more details.

回答2:

Using MapStruct you are missing a step using the @Mapper annotation. The @Mapper will create the implementation of the mappings.

You should review the docs at this link http://mapstruct.org/documentation/stable/reference/html/

Specifically

Defining a mapper

In this section you’ll learn how to define a bean mapper with MapStruct and which options you have to do so. 3.1 Basic mappings

To create a mapper simply define a Java interface with the required mapping method(s) and annotate it with the org.mapstruct.Mapper annotation:
@Mapper
public interface CarMapper {

    @Mappings({
        @Mapping(source = "make", target = "manufacturer"),
        @Mapping(source = "numberOfSeats", target = "seatCount")
    })
    CarDto carToCarDto(Car car);

    @Mapping(source = "name", target = "fullName")
    PersonDto personToPersonDto(Person person);
}
The @Mapper annotation causes the MapStruct code generator to create an implementation of the CarMapper interface during build-time.

来源：https://stackoverflow.com/questions/34130599/mapstruct-mapping-2-objects-to-a-3rd-one

标签

java

object-object-mapping

mapstruct