solution

src/main/java/koz01/java2/lab09/BaseEntity.java

+package koz01.java2.lab09;
+
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+import javax.persistence.MappedSuperclass;
+import javax.persistence.SequenceGenerator;
+
+import lombok.EqualsAndHashCode;
+import lombok.Getter;
+
+@MappedSuperclass
+@EqualsAndHashCode
+public abstract class BaseEntity {
+
+	@Id
+	@Getter
+	@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "seq_post")
+	@SequenceGenerator(name = "seq_post", allocationSize = 1)
+	private Long id;
+}

src/main/java/koz01/java2/lab09/Course.java

 package koz01.java2.lab09;
 
-import java.util.Set;
+import javax.persistence.Entity;
 
-public class Course {
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.EqualsAndHashCode;
+import lombok.NoArgsConstructor;
+
+@Data
+@EqualsAndHashCode(callSuper = true)
+@NoArgsConstructor
+@AllArgsConstructor
+@Builder
+@Entity
+public class Course extends BaseEntity {
 
-	private Set<Student> students;
 
 	private String code;
 

src/main/resources/META-INF/persistence.xml

@@ -20,7 +20,7 @@
    xsi:schemaLocation="
         http://java.sun.com/xml/ns/persistence
         http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
-   <persistence-unit name="primary" transaction-type="RESOURCE_LOCAL">
+   <persistence-unit name="lab09" transaction-type="RESOURCE_LOCAL">
       <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
       
       <!-- HSQL -->
@@ -29,7 +29,7 @@
          data source, this example data source is just for development and testing! -->
       <properties>
          <!-- Properties for Hibernate -->
-          <property name="javax.persistence.jdbc.url" value="jdbc:derby:db/lab09;create=true" />
+          <property name="javax.persistence.jdbc.url" value="jdbc:derby:db/demoDb;create=true" />
           <property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.EmbeddedDriver" />
 
           <property name="hibernate.show_sql" value="true" />

src/test/java/koz01/java2/lab09/Lab09Test.java

+package koz01.java2.lab09;
+
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+import java.util.List;
+
+import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+import javax.persistence.EntityTransaction;
+import javax.persistence.Persistence;
+import javax.persistence.Query;
+
+import org.junit.jupiter.api.Test;
+
+import lombok.extern.log4j.Log4j2;
+
+@Log4j2
+public class Lab09Test {
+
+	@Test
+	public void obtainEntityManager() {
+
+		EntityManagerFactory emf = Persistence.createEntityManagerFactory("lab09");
+		assertNotNull(emf);
+		EntityManager em = emf.createEntityManager();
+		assertNotNull(em);
+		emf.close();
+	}
+
+	@Test
+	public void createCourse() {
+
+
+
+		for (int i = 0; i < 10; i++) {
+			EntityManager em = createEntityManager();
+
+			EntityTransaction trx = em.getTransaction();
+			trx.begin();
+			Course course = Course.builder().code("46012").name("Java II").build();
+			assertNull(course.getId());
+			em.persist(course);
+			assertNotNull(course.getId());
+			Long id = course.getId();
+			em.flush();
+			trx.commit();
+
+			em.close();
+
+			em = createEntityManager();
+			Course course2 = em.find(Course.class, id);
+			assertNotNull(course2);
+			log.info("course == course2: {}", course == course2);
+			em.close();
+
+		}
+	}
+
+	@Test
+	public void removeCourse() {
+		EntityManager em = createEntityManager();
+
+		Course course = Course.builder().code("46012").name("Java II").build();
+
+		em.getTransaction().begin();
+		em.persist(course);
+		Long id = course.getId();
+		em.flush();
+		em.getTransaction().commit();
+		em.close();
+
+		em = createEntityManager();
+		course = em.find(Course.class, id);
+		assertNotNull(course);
+		em.close();
+
+		em = createEntityManager();
+		course = em.find(Course.class, id);
+		em.getTransaction().begin();
+		em.remove(course);
+		em.flush();
+		em.getTransaction().commit();
+		log.info("course = {} was not deleted with id = {}", course, id);
+		em.close();
+
+		em = createEntityManager();
+		course = em.find(Course.class, id);
+		assertNull(course);
+		em.close();
+	}
+
+	@Test
+	public void query() {
+		EntityManager em = createEntityManager();
+
+		Query query = em.createQuery(
+			"select c from Course as c where c.name LIKE ?1");
+		query.setParameter(1, "%Java%");
+		List list = query.getResultList();
+		for (Object obj : list) {
+			log.info("obj: {}, id: {}", obj, ((BaseEntity) obj).getId());
+		}
+
+		em.close();
+	}
+
+	private EntityManager createEntityManager() {
+		return Persistence.createEntityManagerFactory("lab09")
+			.createEntityManager();
+	}
+}