Chapter 24. Gather the domain objects in a planning solution
A TimeTable instance wraps all Timeslot, Room, and Lesson instances of a single dataset. Furthermore, because it contains all lessons, each with a specific planning variable state, it is a planning solution and it has a score:
-
If lessons are still unassigned, then it is an uninitialized solution, for example, a solution with the score
-4init/0hard/0soft. -
If it breaks hard constraints, then it is an infeasible solution, for example, a solution with the score
-2hard/-3soft. -
If it adheres to all hard constraints, then it is a feasible solution, for example, a solution with the score
0hard/-7soft.
The TimeTable class has an @PlanningSolution annotation, so Red Hat Business Optimizer knows that this class contains all of the input and output data.
Specifically, this class is the input of the problem:
A
timeslotListfield with all time slots- This is a list of problem facts, because they do not change during solving.
A
roomListfield with all rooms- This is a list of problem facts, because they do not change during solving.
A
lessonListfield with all lessons- This is a list of planning entities because they change during solving.
Of each
Lesson:-
The values of the
timeslotandroomfields are typically stillnull, so unassigned. They are planning variables. -
The other fields, such as
subject,teacherandstudentGroup, are filled in. These fields are problem properties.
-
The values of the
However, this class is also the output of the solution:
-
A
lessonListfield for which eachLessoninstance has non-nulltimeslotandroomfields after solving -
A
scorefield that represents the quality of the output solution, for example,0hard/-5soft
Procedure
Create the src/main/java/com/example/domain/TimeTable.java class:
package com.example.domain;
import java.util.List;
import org.optaplanner.core.api.domain.solution.PlanningEntityCollectionProperty;
import org.optaplanner.core.api.domain.solution.PlanningScore;
import org.optaplanner.core.api.domain.solution.PlanningSolution;
import org.optaplanner.core.api.domain.solution.drools.ProblemFactCollectionProperty;
import org.optaplanner.core.api.domain.valuerange.ValueRangeProvider;
import org.optaplanner.core.api.score.buildin.hardsoft.HardSoftScore;
@PlanningSolution
public class TimeTable {
@ValueRangeProvider(id = "timeslotRange")
@ProblemFactCollectionProperty
private List<Timeslot> timeslotList;
@ValueRangeProvider(id = "roomRange")
@ProblemFactCollectionProperty
private List<Room> roomList;
@PlanningEntityCollectionProperty
private List<Lesson> lessonList;
@PlanningScore
private HardSoftScore score;
private TimeTable() {
}
public TimeTable(List<Timeslot> timeslotList, List<Room> roomList,
List<Lesson> lessonList) {
this.timeslotList = timeslotList;
this.roomList = roomList;
this.lessonList = lessonList;
}
// ********************************
// Getters and setters
// ********************************
public List<Timeslot> getTimeslotList() {
return timeslotList;
}
public List<Room> getRoomList() {
return roomList;
}
public List<Lesson> getLessonList() {
return lessonList;
}
public HardSoftScore getScore() {
return score;
}
}The value range providers
The timeslotList field is a value range provider. It holds the Timeslot instances which Red Hat Business Optimizer can pick from to assign to the timeslot field of Lesson instances. The timeslotList field has an @ValueRangeProvider annotation to connect those two, by matching the id with the valueRangeProviderRefs of the @PlanningVariable in the Lesson.
Following the same logic, the roomList field also has an @ValueRangeProvider annotation.
The problem fact and planning entity properties
Furthermore, Red Hat Business Optimizer needs to know which Lesson instances it can change as well as how to retrieve the Timeslot and Room instances used for score calculation by your TimeTableConstraintProvider.
The timeslotList and roomList fields have an @ProblemFactCollectionProperty annotation, so your TimeTableConstraintProvider can select from those instances.
The lessonList has an @PlanningEntityCollectionProperty annotation, so Red Hat Business Optimizer can change them during solving and your TimeTableConstraintProvider can select from those too.
