How to map HashMap with Array List of Objects (list is the value in the hash map) into another HashMap using DozerBeanMapper?

Question

I have two classes and want to map the properties from Female object to Male object using org.dozer.Mapper(http://dozer.sourceforge.net/).

The first class is:

public class Male {
    private String name;
    private String surname;

    private Map<String, List<Contact>> contacts;
....

and the second class is :

public class Female {
    private String name;
    private String surname;
    private String mobile;
    private String dateOfBirth;

    private Map<String, List<Contact>> contacts;
...

and the third class is :

public class Contact {
    private String street;
    private String postcode;
    private String email;
...

The Map that i am using like object property is LinkedHashMap and the List which is a value in the Map is ArrayList. When I try to map them using the dozer, the array list which is the value in the hash map is not a list with objects and looks like in the picture:

        Map<String, List<Contact>> contact = new LinkedHashMap<>();
        List<Contact> listOfContacts = new ArrayList<>();
        Contact contactObj = new Contact();
        contactObj.setEmail("lala@gmail.com");
        contactObj.setPostcode("1233355");
        contactObj.setStreet("street");

        listOfContacts.add(contactObj);

        contact.put("2131323213", listOfContacts);
        femaleObj.setContact(contact);

        Mapper objectMapper = new DozerBeanMapper();
        Male maleObj = objectMapper.map(femaleObj, Male.class);

How can I get the list of objects in the List in the Male object?

this is a very vague question. you only show that you map a `female` to a `Male` via `Male maleObj = objectMapper.map(femaleObj, Male.class);` without showing _how_ that is done; besides nowhere does a `LinkedHashMap` or an `ArrayList` appear in the code you posted. — Eugene, Jul 16 '19 at 08:20
*How can I get the list of objects in the List in the Male object* - this makes little sense — Eugene, Jul 16 '19 at 08:43
The List with objects(instances from the Contact class) is not mapped properly in my Male object as it should be. You can see it from the picture that I posted. — ilce, Jul 16 '19 at 08:44
the picture you posted shows an instance of a `Contact` in that `List`. what is wrong with that? — Eugene, Jul 16 '19 at 08:45

Valerio Emanuele · Accepted Answer · 2019-07-16T13:20:16.490

At first, I've tried your code as-is and I got the same behavior.

Then, I've explicit set the mapping configuration with b-hint (see documentation about this) as follow and I got what you need.

First case - Java Configuration (create a class that extends BeanMappingBuilder):

public class CustomMapper extends BeanMappingBuilder {
    @Override
    protected void configure() {
        mapping(Female.class, Male.class).fields("contacts", "contacts", FieldsMappingOptions.hintB(Contact.class));
    }
}

Second case - XML Configuration:

<?xml version="1.0" encoding="UTF-8"?>
<mappings xmlns="http://dozer.sourceforge.net"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://dozer.sourceforge.net
          http://dozer.sourceforge.net/schema/beanmapping.xsd">

  <configuration>
    <stop-on-errors>true</stop-on-errors>
    <wildcard>true</wildcard>
  </configuration>

  <mapping>
    <class-a>blog.valerioemanuele.dozer.Female</class-a>
    <class-b>blog.valerioemanuele.dozer.Male</class-b>

      <field>
        <a>contacts</a>
        <b>contacts</b>
        <b-hint>blog.valerioemanuele.dozer.Contact</b-hint> 
      </field>
  </mapping> 


</mappings>

Here the unit tests I've executed:

import org.dozer.DozerBeanMapper;
import org.junit.Assert;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;

class TestFemaleToMaleConversion {

    private static Female femaleObj;

    @BeforeAll
    private static void initData() {
        Map<String, List<Contact>> contact = new LinkedHashMap<>();
        List<Contact> listOfContacts = new ArrayList<>();
        Contact contactObj = new Contact();
        contactObj.setEmail("lala@gmail.com");
        contactObj.setPostcode("1233355");
        contactObj.setStreet("street");

        listOfContacts.add(contactObj);

        contact.put("2131323213", listOfContacts);
        femaleObj = new Female();
        femaleObj.setName("Elisabeth");
        femaleObj.setSurname("Chesny");
        femaleObj.setContacts(contact);
    }

    @Test
    void testWithXmlMapping() {
        DozerBeanMapper objectMapper = new DozerBeanMapper();
        objectMapper.setMappingFiles(Arrays.asList("dozer-mapping.xml"));
        Male maleObj = objectMapper.map(femaleObj, Male.class);

        Assert.assertEquals("lala@gmail.com", maleObj.getContacts().get("2131323213").get(0).getEmail());
    }

    @Test
    void testWithJavaMapping() {
        DozerBeanMapper objectMapper = new DozerBeanMapper();
        objectMapper.addMapping(new CustomMapper());
        Male maleObj = objectMapper.map(femaleObj, Male.class);

        Assert.assertEquals("street", maleObj.getContacts().get("2131323213").get(0).getStreet());
    }
}

Here the result:

You can get the complete code from my GitHub repository. The example was developed with Java8, Maven and Junit5.

EDIT: I've added Java mapping configuration case. Taking inspiration from another post

score 2 · Answer 2 · answered Jul 16 '19 at 12:24

If you wanna achieve the same with JAVA code instead XML config use this:

public class DemoProvider extends BeanMappingBuilder {

    @Override
    protected void configure() {
        mapping(Female.class, Male.class,
                TypeMappingOptions.oneWay()
        )
                .fields("contact", "contact",
                        FieldsMappingOptions.collectionStrategy(true, RelationshipType.NON_CUMULATIVE),
                        FieldsMappingOptions.hintA(Contact.class),
                        FieldsMappingOptions.hintB(Contact.class),
                        FieldsMappingOptions.oneWay()
                );
      }

}

usage:

DemoProvider demoProvider = new DemoProvider();
DozerBeanMapper objectMapper = new DozerBeanMapper();
objectMapper.addMapping(demoProvider);
Male maleObj = objectMapper.map(femaleObj, Male.class);

How to map HashMap with Array List of Objects (list is the value in the hash map) into another HashMap using DozerBeanMapper?

2 Answers2