Chapter 22. Model the domain objects

Procedure

1. Create the src/main/java/com/example/domain/Timeslot.java class:

   package com.example.domain;
   
   import java.time.DayOfWeek;
   import java.time.LocalTime;
   
   public class Timeslot {
   
       private DayOfWeek dayOfWeek;
       private LocalTime startTime;
       private LocalTime endTime;
   
       private Timeslot() {
       }
   
       public Timeslot(DayOfWeek dayOfWeek, LocalTime startTime, LocalTime endTime) {
           this.dayOfWeek = dayOfWeek;
           this.startTime = startTime;
           this.endTime = endTime;
       }
   
       @Override
       public String toString() {
           return dayOfWeek + " " + startTime.toString();
       }
   
       // ********************************
       // Getters and setters
       // ********************************
   
       public DayOfWeek getDayOfWeek() {
           return dayOfWeek;
       }
   
       public LocalTime getStartTime() {
           return startTime;
       }
   
       public LocalTime getEndTime() {
           return endTime;
       }
   
   }

   Notice the toString() method keeps the output short so it is easier to read Red Hat Business Optimizer’s DEBUG or TRACE log, as shown later.

2. Create the src/main/java/com/example/domain/Room.java class:

   package com.example.domain;
   
   public class Room {
   
       private String name;
   
       private Room() {
       }
   
       public Room(String name) {
           this.name = name;
       }
   
       @Override
       public String toString() {
           return name;
       }
   
       // ********************************
       // Getters and setters
       // ********************************
   
       public String getName() {
           return name;
       }
   
   }

3. Create the src/main/java/com/example/domain/Lesson.java class:

   package com.example.domain;
   
   import org.optaplanner.core.api.domain.entity.PlanningEntity;
   import org.optaplanner.core.api.domain.variable.PlanningVariable;
   
   @PlanningEntity
   public class Lesson {
   
       private Long id;
   
       private String subject;
       private String teacher;
       private String studentGroup;
   
       @PlanningVariable(valueRangeProviderRefs = "timeslotRange")
       private Timeslot timeslot;
   
       @PlanningVariable(valueRangeProviderRefs = "roomRange")
       private Room room;
   
       private Lesson() {
       }
   
       public Lesson(Long id, String subject, String teacher, String studentGroup) {
           this.id = id;
           this.subject = subject;
           this.teacher = teacher;
           this.studentGroup = studentGroup;
       }
   
       @Override
       public String toString() {
           return subject + "(" + id + ")";
       }
   
       // ********************************
       // Getters and setters
       // ********************************
   
       public Long getId() {
           return id;
       }
   
       public String getSubject() {
           return subject;
       }
   
       public String getTeacher() {
           return teacher;
       }
   
       public String getStudentGroup() {
           return studentGroup;
       }
   
       public Timeslot getTimeslot() {
           return timeslot;
       }
   
       public void setTimeslot(Timeslot timeslot) {
           this.timeslot = timeslot;
       }
   
       public Room getRoom() {
           return room;
       }
   
       public void setRoom(Room room) {
           this.room = room;
       }
   
   }

   The Lesson class has an @PlanningEntity annotation, so Red Hat Business Optimizer knows that this class changes during solving because it contains one or more planning variables.

   The timeslot field has an @PlanningVariable annotation, so Red Hat Business Optimizer knows that it can change its value. In order to find potential Timeslot instances to assign to this field, Red Hat Business Optimizer uses the valueRangeProviderRefs property to connect to a value range provider that provides a List<Timeslot> to pick from. See Chapter 24, Gather the domain objects in a planning solution for information about value range providers.

   The room field also has an @PlanningVariable annotation for the same reasons.