How to execute a query using @Query Spring JPA annotation

Question

I am trying to write a query using SpringData Jpa using the @Query annotation on the interface method declaration.

The interface looks like this:

public interface MyService {

    @Query("select * from employee e where e.projectId = ?1")
    public List<Employee> getEmployeesWorkingOnAProject(String projectId) throws MyException;
}

I also have a class that implements this interface:

@Component
public class ProjectServiceImpl implements ProjectService {

}

I am not sure how will this query execution work and how to provide an implementation for getEmployeesWorkingOnAProject method in the imeplementing class.

Thanks

Answer 1

In your Interface, you should extend JpaRepository (or any other spring data repository). Then you can just autowire your interface in any spring bean class and call getEmployeesWorkingOnAProject().

So for example:

public interface MyService extends JpaRepository<Employee,Long> {

    @Query("select * from employee e where e.projectId = ?1")
    public List<Employee> getEmployeesWorkingOnAProject(String projectId) throws MyException;

}


@Component
public class ProjectServiceImpl implements ProjectService {

    private final MyService service;

    @Autowire // not necessary in spring 4.3 +
    public ProjectServiceImpl(MyService service) {
        this.service = service;
    }

    public List<Employee> getEmployeesWorkingOnAProject(String projectId) throws MyException {
         return service.getEmployeesWorkingOnAProject();
    }
}

However, Spring Data is able to build a query for you, so is no reason for writing your own query in this example.

Spring Data way:

public interface MyService extends JpaRepository<Employee,Long> {

    public List<Employee> findAllByProjectId(String projectId) throws MyException;

}

Answer 2

First things first. Your interface have to extend some kind of Spring Data Repository, for example JpaRepository .

Second thing, in the Query annotation, you can put two types of query. JPQL or native SQL query. This can be controlled by a flag on the query annotation (nativeQuery).

In JPQL, your query should look like the following:

@Query("select e from employee e where e.projectId = ?1")