Infobip Spring Data JPA Querydsl

Infobip Spring Data JPA Querydsl provides new functionality that enables the user to leverage the full power of Querydsl API on top of Spring Data repository infrastructure.

Contents

1. News
2. Features and examples
   • Native queries with Querydsl
   • Projections
   • Query
   • Update
   • Delete
   • List instead of Iterable return type
   • Transactional support
   • Stored procedure builder
3. Setup
4. Domain Driven Design concerns
5. Requirements
6. Further reading
7. Running tests
8. Contributing
9. License

News

2.0.1

Changed scope of SimpleExtendedQueryDslJpaRepository to public.

2.0.0

Upgrade to Spring Data 2 (Spring Boot 2).

Breaking change: new repository methods introduced in Spring Data 2 CrudRepository#findById(Object) and QuerydslPredicateExecutor#findOne(Predicate) replace old ExtendedQueryDslJpaRepository.findOneById(Object) and ExtendedQueryDslJpaRepository.findOneByPredicate(Predicate) (they were removed).

Features and examples:

All examples have corresponding tests in the project and can be found here.

Native queries with Querydsl:

Example which uses union clause (unions aren't available in JPA):

List<Person> actual = repository.jpaSqlQuery(query -> query
        .union(
                repository.jpaSqlSubQuery(subQuery ->
                                                  subQuery.select(person)
                                                          .from(person)
                                                          .where(person.firstName.like("John"))),
                repository.jpaSqlSubQuery(subQuery ->
                                                  subQuery.select(person)
                                                          .from(person)
                                                          .where(person.firstName.like("Jan%")))
        )
        .orderBy(person.firstName.asc(), person.lastName.asc())
        .fetch()
);

Projections

For examples how to construct projections refer to the official documentation - section result handling.

Here is an example that uses constructor:

@Value
public class PersonProjection {
    private final String firstName;
    private final String lastName;
}
...
 
List<PersonProjection> actual = repository.query(query -> query
                                          .select(Projections.constructor(PersonProjection.class, person.firstName, person.lastName))
                                          .from(person)
                                          .fetch());

Query

Query exposes full API of JPAQuery (QueryDslPredicateExecutor only exposes where clause (Predicate) and order clause (OrderSpecifier)).

This along with Querydsl 4 API improvement can lead to code that looks more like regular SQL:

List<Person> actual = repository.query(query -> query
        .select(person)
        .from(person)
        .where(person.firstName.in("John", "Jane"))
        .orderBy(person.firstName.asc(), person.lastName.asc())
        .limit(1)
        .offset(1)
        .fetch());

Update

repository.update(query -> query
        .set(person.firstName, "John")
        .where(person.firstName.eq("Johny"))
        .execute());

Delete

long numberOfAffectedRows = repository.deleteWhere(person.firstName.like("John%"));

List instead of Iterable return type

QueryDslPredicateExecutor#findAll methods return Iterable which can be cumbersome to use. Those methods were overridden and now return a List which is easier to use and is easier to convert to Stream.

Transactional support

Query execution is always done inside the repository implementation (loan pattern) in a transaction so transactions don't have to be handled manually (like they do if you are manually managing JPAQuery and other Querydsl constructs).

Stored procedure builder

JPA support for stored procedures is quite cumbersome and it also requires a reference to EntityManager which leads to code like this:

@PersistenceContext
private EntityManager entityManager
...
 
@SuppressWarnings("unchecked")
public List<Person> delete(Person personToDelete) {
    return (List<Person>) entityManager
            .createStoredProcedureQuery("Person_Delete")
            .registerStoredProcedureParameter("FirstName", String.class, ParameterMode.IN)
            .registerStoredProcedureParameter("LastName", String.class, ParameterMode.IN)
            .setParameter("FirstName", personToDelete.getFirstName())
            .setParameter("LastName", personToDelete.getLastName())
            .getResultList(); // returns untyped List => unchecked
}

For this case, executeStoredProcedure method was added which supports Q class attributes:

public List<Person> delete(Person personToDelete) {
    return repository.executeStoredProcedure(
            "Person_Delete",
            builder -> builder.addInParameter(person.firstName, personToDelete.getFirstName())
                              .addInParameter(person.lastName, personToDelete.getLastName())
                              .getResultList());
}

Setup:

1. Dependency:

<dependency>
   <groupId>com.infobip</groupId>
   <artifactId>infobip-spring-data-jpa-querydsl</artifactId>
   <version>${infobip-spring-data-jpa-querydsl.version}</version>
</dependency>

As this project depends on querydsl-apt with jpa classifier you don't need to set up explicit Maven build phase for Q classes generation. For building Q classes without Maven, make sure your IDE has Annotation processing enabled.

2. Add @EnableExtendedRepositories to your Main class:

@EnableExtendedRepositories // replaces @EnableJpaRepositories
@SpringBootApplication
public class Main {
 
    public static void main(String[] args) {
        new SpringApplicationBuilder(Main.class).run(args);
    }
}

3. Refactor repository interfaces to use ExtendedQueryDslJpaRepository instead of JpaRepository and QueryDslPredicateExecutor (note that ExtendedQueryDslJpaRepository extends and provides the API of both):

// ExtendedQueryDslJpaRepository replaces both JpaRepository and QueryDslPredicateExecutor
interface FooRepository extends ExtendedQueryDslJpaRepository<Foo, ID> {
}

4. Done

If you need other features from @EnableJpaRepositories you can use:

@EnableJpaRepositories(repositoryBaseClass = SimpleExtendedQueryDslJpaRepository.class)

Domain Driven Design concerns

In following example one could argue that database related logic has leaked from repository to service layer:

class FooService {

    private final FooRepository repository;
    
    ...
    
    List<Foo> findAll(String barName, Long limit, Long offset) {
        
        ...
        
        return repository.query(query -> query.select(foo)
                                              .from(foo)
                                              .where(foo.bar.name.eq(barName))
                                              .limit(limit)
                                              .offset(offset)
                                              .fetch());
    }
}

In order to prevent this, you can customize the repository.

First, create a custom repository:

interface FooCustomRepository {

    List<Foo> findAll(String barName, Long limit, Long offset);
}

Make FooRepository extend FooCustomRepository:

interface FooRepository extends ExtendedQueryDslJpaRepository<Foo, ID>, FooCustomRepository {
}

Provide an implementation for FooCustomRepository:

class FooCustomRepositoryImpl implements FooCustomRepository {

    private final ExtendedQueryDslJpaRepository<Foo, ID> repository;

    FooCustomRepositoryImpl(@Lazy ExtendedQueryDslJpaRepository<Foo, ID> repository) {
        this.repository = repository;
    }
    
    @Override
    public List<Foo> findAll(String barName, Long limit, Long offset) {
        return repository.query(query -> query.select(foo)
                                              .from(foo)
                                              .where(foo.bar.name.eq(barName))
                                              .limit(limit)
                                              .offset(offset)
                                              .fetch());
    }
}

Refactor service layer to use the new method:

class FooService {

    private final FooRepository repository;
    
    ...
    
    List<Foo> findAll(String barName, Long limit, Long offset) {
        
        ...
        
        return repository.findAll(barName, limit, offset);
    }
}

Requirements:

• Java 8
• Hibernate (if you need support for other JPA implementors please open an issue)
• Spring Data
• Querydsl

Further reading

• Querydsl documentation
• Atlassian Querydsl examples
• Querydsl google group
• Spring Data JPA documentation

Running tests

Tests require SQL Server DB.

Easies way to set it up on your machine is to use docker:

docker run -e 'ACCEPT_EULA=Y' -e 'SA_PASSWORD=<YourStrong!Passw0rd>' -p 1433:1433 -d microsoft/mssql-server-linux:2017-latest

Contributing

If you have an idea for a new feature or want to report a bug please use the issue tracker.

Pull requests are welcome!

License

This library is licensed under the Apache License, Version 2.0.