Select only specific column in Spring with Querydsl?

Question

Let say i have model called Employee with 70 column. How can i implement query SELECT id from t_employee in spring + querydsl without modifying lot of code from this code.

BooleanExpression paramEmployee = qEmployee.company.id.eq(new Long(data.get("company").toString()));
Iterable<Employee> employeeReportIterable =employeeRepository.findAll(paramEmployee);

Answer 1

If You want to use QueryDSL predicate and have single attribute response you could use just QueryDSL directly without using spring-data.

// where entityManager is a JPA EntityManager
JPAQuery<?> query = new JPAQueryFactory(entityManager);

BooleanExpression paramEmployee = qEmployee.company.id.eq(new Long(data.get("company").toString()));

List<Long> id = query.select(qEmployee.id).from(qEmployee).where(paramEmployee).fetch();

Answer 2

I'm afraid querydsl integration with spring only allows for construction of dynamic predicates and not full queries as indicated per spring data documentation.

I suppose though you could just use the getId() method from your Employee class without modifying the code.