Hey Lukas!
I'm following up on my stackOverflow comment on
https://stackoverflow.com/questions/53122656/mapping-jooq-join-result-into-multiple-pojos#comment94047335_53122656.
When stepping away from JPA and using something like jooq, I miss the way
that JPA provides you with a object graph.
Let's say we have the tables `university`, `department` and `employee` and
we want to join them, then get a Java representation something like:
public class University {
private final Long id;
private final List<Department> departments;
// some other fields
}
pubic class Department {
private final Long id;
private final Long universityId;
private final List<Employee> employees;
// some other fields
}
public class Employee {
private final Long id;
private final Long departmentId;
// some other fields
}
>From jooq, we get the denormalised list of pojos that represent a row. When
putting it into the desired structure, the best I've come up with is
overriding the `equals` method to compare `id` and using Java 8 streams.
E.G. (assume a builder for each class)
List<University> universities = rows
.stream()
.map(p -> University
.builder()
.id(p.getUniverisityId())
// some other fields
.build())
.distinct()
.collect(Collectors.toList());
List<Department> departments = rows
.stream()
.map(p -> Department
.builder()
.id(p.getDepartmentId())
// some other fields
.build())
.distinct()
.collect(Collectors.toList());
Map<Long, List<Department>> universityDepartment = departments
.stream()
.collect(Collectors.
groupingBy(Department::getUniversityId));
universities = //loop through universities, set the departments based on
universityDepartment
map (I'm using lombok so would stream and map again using `toBuilder()`)
I feel like I'm missing a trick. Is there a better way?
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