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How to add custom method to Spring Data JPA

java
spring-data-jpa
custom-methods
repository-patterns
Anton ShumikhinbyAnton ShumikhinยทOct 13, 2024
โšกTLDR

To effortlessly integrate a custom method within a Spring Data JPA repository, follow these steps:

  1. Create a custom interface: Declare your method in this interface.
  2. Implement the interface: Create an implementation class annotated with @Repository.
  3. Extend your JPA repository interface: Add your custom interface to your JPA repository.

Let's see it in action:

// Custom operations interface
public interface CustomRepository {
    List<MyEntity> findByNameLike(String namePattern);
}

// Captain's log: Implementing custom behavior
// Artificial gravity fully functional ๐Ÿš€
@Repository
public class CustomRepositoryImpl implements CustomRepository {
    @PersistenceContext
    private EntityManager entityManager;

    @Override
    public List<MyEntity> findByNameLike(String namePattern) {
        // Scotty? We need a QueryDSL or EntityManager for warp speed!
        return entityManager.createQuery(
        "FROM MyEntity e WHERE e.name LIKE :namePattern", 
        MyEntity.class)
            .setParameter("namePattern", namePattern)
            .getResultList();
    }
}

// Extending Spring Data repository with custom operations
// Engaging warp drive in 3..2..1...
public interface MyEntityRepository extends JpaRepository<MyEntity, Long>, CustomRepository {
    // Standard Spring Data methods โœจ
}

Now, go explore the universe with MyEntityRepository as it can invoke both predefined and custom query methods.

Implementing custom methods: The nuts and bolts

The magic of Impl suffix

Spring bestows upon us a convention where the custom implementation must end with Impl. This visibility cloak helps Spring to magically detect and couple custom code with the corresponding repository.

Twist the EntityManager for detailed queries

The @PersistenceContext annotation brings forth the EntityManager into your custom repository, giving you the power to brew special queries outside the limited realm of Spring Data's method names.

Breaking the circular dependency chain

Beware of the horrid circular dependencies. To escape this curse, use constructor-based injection over field injection with @Autowired. This ensures the dependencies are immutable, thus forming a cleaner codebase.

Increase productivity with custom query methods

Custom query methods are productivity-enhancing spells that leverage Spring's capabilities without much toil. They achieve entity manipulation and complex queries with the snap of your fingers.

Keeping codebase clean and maintainable

As a good citizen of the coding world, consider the team and project size when you bring in custom methods. Use @SuppressWarnings to keep warnings for unused custom methods at bay in large projects. Keep your codebase clean by limiting the custom implementation to one Impl class per repository.

Simple requirements? Use default methods

For simple custom needs, utilize default methods within the interface. It saves time as it evades the need for a separate implementation.

Custom methods: The real superheroes

Spring Data repositories offer CRUD operations and query generation, no doubt. But when you have to save the world from a complex business requirement, the custom methods come to your rescue.

explain-codes / Java / How to add custom method to Spring Data JPA
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๎“ขLinked

Spring CrudRepository findByInventoryIds(List<Long> inventoryIdList) - equivalent to IN clause

๏”

What is the difference between @Inject and @Autowired in Spring Framework? Which one to use under what condition?

๏”

How to fetch FetchType.LAZY associations with JPA and Hibernate in a Spring Controller

๏”

What exactly is Spring Framework for?

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Consider defining a bean of type 'package' in your configuration [Spring-Boot]

๏”

What's the difference between @Component, @Repository & @Service annotations in Spring?

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What is the difference between CrudRepository and JpaRepository interfaces in Spring Data JPA?

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