Spring: ApplicationStartingEvent cannot be cast to ApplicationPreparedEvent for OptaPlanner Examination App - spring

Question

I'm a newbie and I try to start a Spring application linked to Optaplanner which will solve and place exams on a timetable.
I fixed the various issues with missing jars and I started the app on main.
However, it gives error:
Exception in thread "main" java.lang.ClassCastException: class org.springframework.boot.context.event.ApplicationStartingEvent cannot be cast to class org.springframework.boot.context.event.ApplicationPreparedEvent (org.springframework.boot.context.event.ApplicationStartingEvent and org.springframework.boot.context.event.ApplicationPreparedEvent are in unnamed module of loader 'app')
Here is the TimeTable class :
package models;
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.ProblemFactCollectionProperty;
import org.optaplanner.core.api.domain.valuerange.ValueRangeProvider;
import org.optaplanner.core.api.score.buildin.hardsoft.HardSoftScore;
#PlanningSolution
public class Timetable {
#ValueRangeProvider(id = "PeriodeRange")
#ProblemFactCollectionProperty
public List<Periode> periodeList;
#ValueRangeProvider(id = "SalleRange")
#ProblemFactCollectionProperty
public List<Salle> salleList;
#PlanningEntityCollectionProperty
public List<Examen> examenList;
#PlanningScore
public HardSoftScore score;
public void TimeTable(List<Periode> periodeList, List<Salle> roomList,
List<Examen> examenList) {
this.periodeList = periodeList;
this.salleList = roomList;
this.examenList = examenList;
}
public List<Periode> getperiodeList() {
return periodeList;
}
public List<Salle> getsalleList() {
return salleList;
}
public List<Examen> getexamenList() {
return examenList;
}
public HardSoftScore getScore() {
return score;
}
}
And the class that defines the solver :
package models;
import java.util.UUID;
import java.util.concurrent.ExecutionException;
import modeles.Timetable;
import org.optaplanner.core.api.solver.SolverJob;
import org.optaplanner.core.api.solver.SolverManager;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
#RestController
#RequestMapping("/Timetable")
public class TimetableController {
#Autowired
public SolverManager<Timetable, UUID> solverManager;
#PostMapping("/solve")
public Timetable solve(#RequestBody Timetable problem) {
UUID problemId = UUID.randomUUID();
// Submit the problem to start solving
SolverJob<Timetable, UUID> solverJob = solverManager.solve(problemId, problem);
Timetable solution;
try {
// Wait until the solving ends
solution = solverJob.getFinalBestSolution();
} catch (InterruptedException | ExecutionException e) {
throw new IllegalStateException("Solving failed.", e);
}
return solution;
}
}
And here is the main :
package models;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
#SpringBootApplication
public class TimeTableSpringBootApp {
public static void main(String[] args) {
System.setProperty("spring.devtools.restart.enabled", "false");
SpringApplication.run(TimeTableSpringBootApp.class, args);
}
}
Any answer would be gladly appreciated.
Thank you in advance.

Answer 1

I suspect your project's dependency tree somehow has that spring class ApplicationStartingEvent twice in it's classpath (coming from different jars), which causes the class cast exception.
Try running mvn dependency:tree on your project and the optaplanner spring boot school timetabling quickstart. I suspect you're mixing spring versions in your dependency tree.