Conversion of DTO to entity and vice-versa

Question

I am using Spring MVC architecture with JPA in my web application. Where to convert data transfer object (DTO) to JPA entity and vice-versa, manually (that is, without using any framework)?

Answer 1

This is an old question with accepted answer but though to update it with easy way of doing it using model-mapper API.

<dependency>     <groupId>org.modelmapper</groupId>     <artifactId>modelmapper</artifactId>     <version>0.7.4</version> </dependency> 

Using this API, you avoid manual setter & getters as explained in accepted answer.

In my opinion, both conversions should happen at controller with the help of private utility methods and using Java8 stream's map ( if a Collection of DTOs is exchanged ) like illustrated in this article.

It should happen at controller because DTOs are meant to be exclusive transfer objects. I don't take my DTOs further way down.

You code your service & data access layers on entities and convert DTOs to entities before calling service methods & convert entities to DTOs before returning response from controller.

I prefer this approach because entities rarely change and data can be added / removed from DTOs as desired.

Detailed model mapper configuration and rules are described here

Answer 2

I suggest another approach without extra dependency:

import org.springframework.beans.BeanUtils ... BeanUtils.copyProperties(sourceObject, targetObject); 

Can be used to convert DTO to entity, or vice-versa, if they have same property types and names.

If you want to ignore some fields, just add them after the targetObject.

BeanUtils.copyProperties(sourceObj, targetObj, "propertyToIgnoreA", "propertyToIgnoreB", "propertyToIgnoreC"); 

Source: http://appsdeveloperblog.com/dto-to-entity-and-entity-to-dto-conversion/

I think this is the cleanest way. Remember to check the Javadoc for caveats!