Decorators

Decorate mapping operations with additional logic.

In some use cases mapping fields is not enough. Sometimes we need to add additional logic to the mapping. For these use cases we have the decorators, the decorators allow us to perform operations on our models after the mapping has finished.

We start with our two classes, our source class User and our destination class UserDisplay.

Kotlin

data class User(
    var firstName: String,
    var lastName: String
)

Java

public class User {
    private String firstName;
    private String lastName;

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
}

Kotlin

data class UserDisplay(
    var firstName: String,
    var lastName: String,
    var fullName: String
)

Java

public class UserDisplay {
    private String firstName;
    private String lastName;
    private String fullName;

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getFullName() {
        return fullName;
    }

    public void setFullName(String fullName) {
        this.fullName = fullName;
    }
}

In this example, we want to merge the firstName and lastName fields to the fullName field.

Adding Decorators

Adding decorators is available through the ShapeShiftBuilder class. Decorators can be added inline or as a separate class.

Class Decorators

To create a decorator class implement the MappingDecorator interface.

Kotlin

class UserUserDisplayDecorator : MappingDecorator<User, UserDisplay> {
    override fun decorate(context: MappingDecoratorContext<User, UserDisplay>) {
        val (from, to) = context
        to.fullName = "${from.firstName} ${from.lastName}"
    }
}

Java

public class UserUserDisplayDecorator implements MappingDecorator<User, UserDisplay> {
    @Override
    public void decorate(@NonNull MappingDecoratorContext<User, UserDisplay> mappingDecoratorContext) {
        User from = mappingDecoratorContext.getFrom();
        UserDisplay to = mappingDecoratorContext.getTo();
        to.setFullName(from.getFirstName() + " " + from.getLastName());
    }
}

And register it to the ShapeShift instance.

Kotlin

val shapeShift = ShapeShiftBuilder()
    .withDecorator(UserUserDisplayDecorator())
    .build()

Java

ShapeShift shapeShift = new ShapeShiftBuilder()
        .withDecorator(User.class, UserDisplay.class, new UserUserDisplayDecorator())
        .build();

Inline Decorators

It is also possible to add the decorator logic inline.

Kotlin

val shapeShift = ShapeShiftBuilder()
    .withDecorator(MappingDecorator<User, UserDisplay> {
        val (from, to) = it
        to.fullName = "${from.firstName} ${from.lastName}"
    })
    .build()

Java

ShapeShift shapeShift = new ShapeShiftBuilder()
        .withDecorator(User.class, UserDisplay.class, mappingDecoratorContext -> {
            User from = mappingDecoratorContext.getFrom();
            UserDisplay to = mappingDecoratorContext.getTo();
            to.setFullName(from.getFirstName() + " " + from.getLastName());
        })
        .build();