springhibernateormdtoobject-model

Retrieving foreign key attributes in DTO

I am using java+Spring framework+Hibernate for creating rest api but I have stumbled upon retrieving details of a table using foreign key attributes. I have the following tables::

https://i.sstatic.net/lG7UR.png

I am retrieving all the ratings given using product id and then mapping to DTO, now I also want to populate the username using idusers as this is my foreign key.

Same is the case when I try to retrieve ratings given by the users, instead of displaying idproducts I want to display the product name and product description as It is a foreign key.

Any advice on how to do so using DTO's.

Solution

  • You can use ModelMapper when converting a DTO to an Entity bean and back from Entity bean to a DTO.

    Add ModelMapper to your project

    <dependency>
<groupId>org.modelmapper</groupId>
<artifactId>modelmapper</artifactId>
<version>2.3.5</version>
</dependency>

    Define the ModelMapper bean in your Spring configuration

    @Bean
public ModelMapper modelMapper() {
return new ModelMapper();
}

    Assuming the following models based on the given ER diagram you have given

    public class UserDto {
Integer userId;
String role;
String username;
String password;
boolean enabled;
...default and parameterized constructor
...getter and setter methods
}


public class ProductDto {
Integer productId;
String imageUrl;
String category;
int productPrice;
int productQuantity;
String productName;
String productDesc;
...default and parameterized constructor
...getter and setter methods
}


public class RatingDto {
@Id
Integer id;
int rating;
String review;
String ratingscol;
ProductDto productDto;
UserDto userDto;
...default and parameterized constructor
...getter and setter methods
}

    You can retrieve the ratings of a product using product id along with the user details by using the following method

     @Repository
 public interface RatingRepository extends JpaRepository<Rating, Integer>{
 List<Rating> findByProduct_ProductId(Integer productId);
 }

    Then mapping rating objects to DTO

     RatingDto ratingDto = modelMapper.map(rating, RatingDto.class);

    Now you can retrieve username as following

     ratingsDto.getUserDto().getUserName()

    The same way you can retrieve the ratings by userId and access product details