Make references transient.

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

@@ -3,6 +3,7 @@ package koz01.java2.lab10;
 import java.util.Set;
 
 import javax.persistence.Entity;
+import javax.persistence.Transient;
 
 import lombok.AllArgsConstructor;
 import lombok.Getter;
@@ -18,6 +19,7 @@ public class Clas extends BaseEntity {
 	@Setter
 	private String cname;
 
+	@Transient
 	@Getter
 	@Setter
 	private Set<Clas> clas;

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

@@ -3,6 +3,7 @@ package koz01.java2.lab10;
 import java.util.List;
 
 import javax.persistence.Entity;
+import javax.persistence.Transient;
 
 import lombok.AllArgsConstructor;
 import lombok.Getter;
@@ -18,6 +19,7 @@ public class Department extends BaseEntity {
 	@Setter
 	private String name;
 
+	@Transient
 	@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 lombok.AllArgsConstructor;
 import lombok.Getter;
@@ -28,6 +29,7 @@ public class Employee extends BaseEntity {
 	@Setter
 	private String deg;
 
+	@Transient
 	@Setter
 	@Getter
 	private Department department;

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

@@ -4,6 +4,7 @@ package koz01.java2.lab10;
 import java.util.Set;
 
 import javax.persistence.Entity;
+import javax.persistence.Transient;
 
 import lombok.AllArgsConstructor;
 import lombok.Getter;
@@ -23,6 +24,7 @@ public class Teacher extends BaseEntity {
 	@Setter
 	private String subject;
 
+	@Transient
 	@Getter
 	@Setter
 	private Set<Clas> clasSet;