[FIXED] ModelMapper reverse map from a destination field onto itself

Issue

Is there a way ModelMapper can reverse map a value already set using PropertyMap again to another field in destination? In other words, I have a computed value and the same has to be set on two fields using PropertyMap, computation changes the value everytime and cannot be invoked twice using(converter).

Solution

Introduction

Let's consider the following versions as the current versions:

• ModelMapper: 3.1.0.

It seems that by the «ModelMapper» library design:

• There is no way to «reuse» the converted source value to set multiple destination property values.

Possible solution

A post-converter may be used to copy a value from one destination property to another.

Draft example program

pom.xml file

<dependency>
    <groupId>org.modelmapper</groupId>
    <artifactId>modelmapper</artifactId>
    <version>3.1.0</version>
</dependency>

Customer class

class Customer {
    private String fullName;

    public String getFullName() {
        return fullName;
    }

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

CustomerDTO class

import java.util.StringJoiner;

class CustomerDTO {
    private String fullName;
    private String copyOfFullName;

    public String getFullName() {
        return fullName;
    }

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

    public String getCopyOfFullName() {
        return copyOfFullName;
    }

    public void setCopyOfFullName(final String copyOfFullName) {
        this.copyOfFullName = copyOfFullName;
    }

    @Override
    public String toString() {
        return new StringJoiner(", ", CustomerDTO.class.getSimpleName() + "[", "]")
            .add("fullName='" + fullName + "'")
            .add("copyOfFullName='" + copyOfFullName + "'")
            .toString();
    }
}

Program class

import org.modelmapper.Converter;
import org.modelmapper.ModelMapper;

public final class Program {
    public static void main(final String[] args) {
        final Customer customer = new Customer();
        customer.setFullName("Full name");

        final ModelMapper modelMapper = new ModelMapper();

        final Converter<Customer, CustomerDTO> customerConverter = context -> {
            final CustomerDTO destination = context.getDestination();
            // NOTE: Copying the value of the full name property to another property.
            destination.setCopyOfFullName(destination.getFullName());
            return destination;
        };
        modelMapper.typeMap(
            Customer.class, CustomerDTO.class
        ).addMapping(
            Customer::getFullName, CustomerDTO::setFullName
        ).setPostConverter(customerConverter);

        modelMapper.validate();

        final CustomerDTO customerDTO = modelMapper.map(customer, CustomerDTO.class);
        System.out.println(customerDTO);
    }
}

Output

CustomerDTO[fullName='Full name', copyOfFullName='Full name']

Additional references

• Post-converter example. java - ModelMapper: transferring attribute from root to each elements of a list - Stack Overflow.

  • Answer.

Answered By - Sergey Vyacheslavovich Brunov
Answer Checked By - Candace Johnson (JavaFixing Volunteer)