CODEWITHSUNDEEP
javaspringspring-data-jpa
Serhii
Serhii

Reputation: 7553

How to specify spring data jpa request to load collection of entity properties?

I use spring data JPA. I need in my repository request to load only collection of concrete properties colors:

@Query(value = "SELECT cd.color FROM CalendarDetails cd where cd.userCalendar.userId = :userId")
List<String> findCalendarColorsByUserWithDuplicates(@Param("userId") Long userId);

Provided solution works correctly.

I want simplify it using spring approach to load collection of the repository objects I'd use (repository public interface CalendarDetailsRepository extends JpaRepository<CalendarDetails, Long>):

List<CalendarDetails> findByUserCalendarUserId(@Param("userId") Long userId);

But I need collection of colors! Trying

List<String> findColorByUserCalendarUserId(Long userId);

I get collection of CalendarDetails

Is it possible to improve my last request following spring data approaches to load list of colors?

Upvotes: 1

Views: 854

Answers (2)

dvelopp
dvelopp

Reputation: 4315

You can try special Projection mechanisms that Spring Data provides. It will allow you not only to optimize your queries but also to make it with pure java without using @Query.

There are a lot of ways to make it, but I would recommend the following. You add an interface that contains getters for the properties that you need to take from entity:

public interface ColorOnly {
    String getColor();
}

Then you return the list of this interface' objects:

List<ColorOnly> findColorByUserCalendarUserId(Long userId);

To use the colours from the interface, you just invoke getColor method. You may consider simplifying it with Java 8 streams and map conversions. BTW, this one will only query colour. No other fields will be included into the query Hibernate produces.

Upvotes: 2

reconnect
reconnect

Reputation: 346

Try to add All

findAllByUserCalendarUserId(Long userId);

BTW, IntelliJ IDEA provide very deep support of JPA repositories, so it's prevent a lot of possible issues when you create queries like this one

Upvotes: -1

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