春天如何在包含在对象中的列表上做出选择语句？

Question

How do you make a select statement or filter a List that is nested within an entity in spring? I have an object that looks like this...

@Entity
@Table(name = "employee")
public class Employee {

...

    @OneToMany(mappedBy = "_employee", fetch = FetchType.EAGER, cascade = CascadeType.REMOVE)
    @JsonManagedReference
    Set<Deal> _deals;

    @OneToMany(mappedBy = "_employee", fetch = FetchType.EAGER, cascade = CascadeType.REMOVE)
    @JsonManagedReference //This is simply to avoid a stackoverflow error according to this link http://stackoverflow.com/questions/3325387/infinite-recursion-with-jackson-json-and-hibernate-jpa-issue
    Set<Recommendation> _recommendations;


    @OneToMany(mappedBy = "_employee", fetch = FetchType.EAGER, cascade = CascadeType.REMOVE)
    @JsonManagedReference //This is simply to avoid a stackoverflow error according to this link http://stackoverflow.com/questions/3325387/infinite-recursion-with-jackson-json-and-hibernate-jpa-issue
    Set<Event> _events;

  public Employee() {
    }

//getters and setters

....

I get employees with a repository that is accessed by a service class.

The repository looks like this.

public interface EmployeeRepository extends CrudRepository<Employee, Long> {

    public Employee getEmployeeById(Long _id);

    public Employee getEmployeeBy_username(String username);

}

So bascially when I get an employee by its id, it returns the above lists. When an employee is retrieved I need to do a select statement or filter in some way _deals, _recommendations and _events. So that only those who have the boolean attribute _active=true returned. As it is now, all deals recommendations and events are returned whether they are active or not. How do I filter or select from these lists only active objects?

Answer 1

You almost always select a single Entity type per query, and preferably you would do the filtering in the database. If you want the Deals, Recommendations and Events belonging to a specific Employee, I would normally put these methods in the Repository belonging to entity type I'm trying to load, it could look like this:

@Repository
public interface DealRepository extends JpaRepository<Deal, Long> {

    @Query("select d from Deal d where d.active= true and d.employee.id = :employeeId")
    List<Deal> findActiveDeals(@Param("employeeId") long employeeId);
}