@SpringBootApplication
public class SpringCd244ManyToManyBootApplication {
public static void main(String[] args) {
    SpringApplication.run(SpringCd244ManyToManyBootApplication.class, args);

    // create session factory
            SessionFactory factory = new Configuration()
                                    .configure("hibernate.cfg.xml")
                                    .addAnnotatedClass(Instructor.class)
                                    .addAnnotatedClass(InstructorDetail.class)
                                    .addAnnotatedClass(Course.class)
                                    .addAnnotatedClass(Review.class)
                                    .addAnnotatedClass(Student.class)
                                    .buildSessionFactory();

            // create session
            Session session = factory.getCurrentSession();
            try {....

2018-01-11 20:45:33.261  INFO 5772 --- [  restartedMain] org.hibernate.orm.connections.pooling    : HHH10001008: Cleaning up connection pool [jdbc:mysql://localhost:3306/webapp?useSSL=false]
Exception in thread "restartedMain" java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49)
Caused by: org.hibernate.property.access.spi.PropertyAccessException: Error accessing field [private io.scalando.Instructor io.scalando.Course.instructor] by reflection for persistent property [io.scalando.Course#instructor] : Course [id=0, title=Pacman - How To Score One Million Points]
    at org.hibernate.property.access.spi.GetterFieldImpl.get(GetterFieldImpl.java:74)
    at org.hibernate.tuple.entity.AbstractEntityTuplizer.getPropertyValue(AbstractEntityTuplizer.java:626)