Solution

src/main/java/koz01/java2/lab10/Clas.java

@@ -3,7 +3,7 @@ package koz01.java2.lab10;
 import java.util.Set;
 
 import javax.persistence.Entity;
-import javax.persistence.Transient;
+import javax.persistence.ManyToMany;
 
 import lombok.AllArgsConstructor;
 import lombok.Getter;
@@ -19,7 +19,7 @@ public class Clas extends BaseEntity {
 	@Setter
 	private String cname;
 
-	@Transient
+	@ManyToMany(mappedBy = "clas")
 	@Getter
 	@Setter
 	private Set<Teacher> teacher;

src/main/java/koz01/java2/lab10/Department.java

@@ -3,7 +3,7 @@ package koz01.java2.lab10;
 import java.util.List;
 
 import javax.persistence.Entity;
-import javax.persistence.Transient;
+import javax.persistence.OneToMany;
 
 import lombok.AllArgsConstructor;
 import lombok.Getter;
@@ -21,7 +21,8 @@ public class Department extends BaseEntity {
 	@Setter
 	private String name;
 
-	@Transient
+	@ToString.Exclude
+	@OneToMany(mappedBy = "department")
 	@Getter
 	@Setter
 	private List<Employee> employee;

src/main/java/koz01/java2/lab10/Employee.java

 package koz01.java2.lab10;
 
 import javax.persistence.Entity;
-import javax.persistence.Transient;
+import javax.persistence.ManyToOne;
 
 import lombok.AllArgsConstructor;
 import lombok.Getter;
@@ -28,7 +28,7 @@ public class Employee extends BaseEntity {
 	private String deg;
 
 	@ToString.Exclude
-	@Transient
+	@ManyToOne
 	@Setter
 	@Getter
 	private Department department;

src/main/java/koz01/java2/lab10/NonTeachingStaff.java

 package koz01.java2.lab10;
 
+import javax.persistence.DiscriminatorValue;
 import javax.persistence.Entity;
 
 import lombok.Getter;
@@ -7,6 +8,7 @@ import lombok.NoArgsConstructor;
 import lombok.Setter;
 
 @Entity
+@DiscriminatorValue(value = "nts")
 @NoArgsConstructor
 public class NonTeachingStaff extends Staff {
 

src/main/java/koz01/java2/lab10/Staff.java

 package koz01.java2.lab10;
 
 import javax.persistence.Entity;
+import javax.persistence.Inheritance;
+import javax.persistence.InheritanceType;
 
 import lombok.Getter;
 import lombok.NoArgsConstructor;
 import lombok.Setter;
 
 @Entity
+@Inheritance(strategy = InheritanceType.JOINED)
 @NoArgsConstructor
 public class Staff extends BaseEntity {
 

src/main/java/koz01/java2/lab10/Teacher.java

@@ -4,7 +4,7 @@ package koz01.java2.lab10;
 import java.util.Set;
 
 import javax.persistence.Entity;
-import javax.persistence.Transient;
+import javax.persistence.ManyToMany;
 
 import lombok.AllArgsConstructor;
 import lombok.Getter;
@@ -24,7 +24,7 @@ public class Teacher extends BaseEntity {
 	@Setter
 	private String subject;
 
-	@Transient
+	@ManyToMany
 	@Getter
 	@Setter
 	private Set<Clas> clas;