ModelMapper, mapping list of Entites to List of DTO objects

Question

I am writing simple blog web application using Spring MVC framework. I am willing to add DTO layer to my app.

I decided to use ModelMapper framework for conversion from Entity objects to DTO objects used in my views.

I have just one problem. On my main page, I am showing a list of posts on my blog. In my view, it's just list of Post (Entity) objects. I want to change it to pass a list of PostDTO objects to my view. Is there any way to map List of Post objects to List of PostDTO object with single method call? I was thinking about writing converter that will convert this but I am not sure it's a good way to do it.

Also, I am using Lists of Entities in few more places like administrative panel or comment below every Post on my page.

Link to code of my app on GitHub repository: repository

Answer 1

You can create util class:

public class ObjectMapperUtils {      private static final ModelMapper modelMapper;      /**      * Model mapper property setting are specified in the following block.      * Default property matching strategy is set to Strict see {@link MatchingStrategies}      * Custom mappings are added using {@link ModelMapper#addMappings(PropertyMap)}      */     static {         modelMapper = new ModelMapper();         modelMapper.getConfiguration().setMatchingStrategy(MatchingStrategies.STRICT);     }      /**      * Hide from public usage.      */     private ObjectMapperUtils() {     }      /**      * <p>Note: outClass object must have default constructor with no arguments</p>      *      * @param <D>      type of result object.      * @param <T>      type of source object to map from.      * @param entity   entity that needs to be mapped.      * @param outClass class of result object.      * @return new object of <code>outClass</code> type.      */     public static <D, T> D map(final T entity, Class<D> outClass) {         return modelMapper.map(entity, outClass);     }      /**      * <p>Note: outClass object must have default constructor with no arguments</p>      *      * @param entityList list of entities that needs to be mapped      * @param outCLass   class of result list element      * @param <D>        type of objects in result list      * @param <T>        type of entity in <code>entityList</code>      * @return list of mapped object with <code><D></code> type.      */     public static <D, T> List<D> mapAll(final Collection<T> entityList, Class<D> outCLass) {         return entityList.stream()                 .map(entity -> map(entity, outCLass))                 .collect(Collectors.toList());     }      /**      * Maps {@code source} to {@code destination}.      *      * @param source      object to map from      * @param destination object to map to      */     public static <S, D> D map(final S source, D destination) {         modelMapper.map(source, destination);         return destination;     } } 

And use it for your needs:

List<PostDTO> listOfPostDTO = ObjectMapperUtils.mapAll(listOfPosts, PostDTO.class); 

Answer 2

considering you have a list of Post Entity (postEntityList) and a PostDTO class, you can try following:

use the following imports to get the desired results

import org.modelmapper.ModelMapper; import org.modelmapper.TypeToken; import java.lang.reflect.Type; 

use the below code

Type listType = new TypeToken<List<PostDTO>>(){}.getType(); List<PostDTO> postDtoList = modelmapper.map(postEntityList,listType);