如何在 Spring 数据休息中返回深层嵌套投影？

Question

鉴于这 3 个实体：

@Entity
class Department{
    Set<Employee> employees;
    Set<Employee> getEmployees(){
        return this.employees;
    };    
}

@Entity
class Employee{
    Nationality nationality;
    Nationality getNationality(){
        this.nationality;
    }
}
@Entity
class Nationality{

}

我想为 Department 创建一个投影，返回所有部门及其员工和国籍。我所取得的成就是让所有部门及其员工使用：

@Projection(name = "fullDepartment", types = { Department.class })
public interface DepartmentsProjection {
    Set<Employee> getEmployees();
}

@RepositoryRestResource(collectionResourceRel = "department", path = "departments")
public interface DepartmentRepository extends JpaRepository<Department, Long> {
}

Answer 1

一种方法是为您的嵌套对象创建一个投影，然后在更全局的对象中使用此投影。因此，根据您的问题，您可以为 Nationality 创建一个投影，然后为 Department 创建另一个具有获取 Nationality 投影的 getter 的投影，最后是另一个获取 Department 实体的投影。

@Projection(name = "NationalityProjection", types = { Nationality.class })
public interface NationalityProjection{
    // getters of all attributes you want to project
}

@Projection(name = "EmployeeProjection", types = { Employee.class })
public interface EmployeeProjection{
    NationalityProjection getNationality();
}

@Projection(name = "DepartmentProjection", types = { Department.class })
public interface DepartmentProjection{
    Set<EmployeeProjection> getEmployees();
}

希望对你有帮助！