Question

I am having a hard time deciding if I should stick with Hibernate for a new project, or get my feet wet with JPA and the new Spring Data implementation.

Is the Spring Data framework intended for large projects or small projects with modest query requirements?

While I certainly see the advantage in code reduction by using the @Query annotation, what do you do for dynamic queries? What about when you want to implement a save() method that’s quite complex?

The documentation says to make a Custom interface and implementation that your main repository implements, but what if you need to access any super methods on the crud repository itself? The crud repository implements the custom one – not the other way around. It seems like an odd design.

I am very uncertain whether this framework will meet the challenges of complex and large applications. I’ve never ran into many problems with Hibernate, and I’m considering sticking with the good old reliable rather than go with Spring Data JPA.

What should I do? What unforeseen complications and costs will I encounter if I go with Spring Data JPA?

Answer 1

So, spring-data does some extra magic that helps with complex queries. It is strange at first and you totally skip it in the docs but it is really powerful and useful.

It involves creating a custom Repository and a custom `RepositoryImpl’ and telling Spring where to find it. Here is an example:

Configuration class – point to your still-needed xml config with annotation pointing to your repositories package (it looks for *Impl classes automatically now):

@Configuration
@EnableJpaRepositories(basePackages = {"com.examples.repositories"})
@EnableTransactionManagement
public class MyConfiguration {
}

jpa-repositories.xml – tell Spring where to find your repositories. Also tell Spring to look for custom repositories with the CustomImpl file name:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:jpa="http://www.springframework.org/schema/data/jpa"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:util="http://www.springframework.org/schema/util"
xsi:schemaLocation="http://www.springframework.org/schema/data/mongo http://www.springframework.org/schema/data/jpa/spring-jpa.xsd
    http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd">

<jpa:repositories base-package="com.example.repositories" repository-impl-postfix="CustomImpl" />

</beans>

MyObjectRepository – this is where you can put annotated and unannotated query methods. Note how this repository interface extends the Custom one:

@Transactional
public interface MyObjectRepository extends JpaRepository<MyObject, Integer>, MyObjectRepositoryCustom {

    List<MyObject> findByName(String name);

    @Query("select * from my_object where name = ?0 or middle_name = ?0")
    List<MyObject> findByFirstNameOrMiddleName(String name);
}

MyObjectRepositoryCustom – repository methods that are more complex and cannot be handled with a simple query or an annotation:

public interface MyObjectRepositoryCustom {

    List<MyObject> findByNameWithWeirdOrdering(String name);
}

MyObjectRepositoryCustomImpl – where you actually implement those methods with an autowired EntityManager:

public class MyObjectRepositoryCustomImpl implements MyObjectRepositoryCustom {

    @Autowired
    private EntityManager entityManager;

    public final List<MyObject> findByNameWithWeirdOrdering(String name) {
        Query query = query(where("name").is(name));
        query.sort().on("whatever", Order.ASC);
        return entityManager.find(query, MyObject.class);
    }
}

Amazingly, this all comes together and methods from both interfaces (and the CRUD interface, you implement) all show up when you do:

myObjectRepository.

You will see:

myObjectRepository.save()
myObjectRepository.findAll()
myObjectRepository.findByName()
myObjectRepository.findByFirstNameOrMiddleName()
myObjectRepository.findByNameWithWeirdOrdering()

It really does work. And you get one interface for querying. spring-data really is ready for a large application. And the more queries you can push into simple or annotation only the better off you are.

All of this is documented at the Spring Data Jpa site.