package com.Employee.Employee;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

import com.Employee.Department.Department;

@Entity
@Table(name = "Employee_1toMany")
public class Employee {
    @Id
    @GeneratedValue
    @Column(name = "EId")
    private int emp_id;
    @Column(name = "EName")
    private String name;
    private Department dept;

    public int getEmp_id() {
        return emp_id;
    }
    public void setEmp_id(int emp_id) {
        this.emp_id = emp_id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    @ManyToOne
    @JoinColumn(name = "DepartmentID")
    public Department getDept() {
        return dept;
    }
    public void setDept(Department dept) {
        this.dept = dept;
    }
}

package com.Employee.Department;

import java.util.List;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;

import com.Employee.Employee.Employee;

@Entity
@Table(name = "Department_1toMany")
public class Department {
    @Id
    @GeneratedValue
    @Column(name = "DId")
    private int Dept_id;
    @Column(name = "DName")
    private String Dept_name;
    private List<Employee> emp;

    public int getDept_id() {
        return Dept_id;
    }
    public void setDept_id(int dept_id) {
        Dept_id = dept_id;
    }
    public String getDept_name() {
        return Dept_name;
    }
    public void setDept_name(String dept_name) {
        Dept_name = dept_name;
    }
    @OneToMany(targetEntity = Employee.class, mappedBy = "dept", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    public List<Employee> getEmp() {
        return emp;
    }
    public void setEmp(List<Employee> emp) {
        this.emp = emp;
    }
}

package com.Employee.MainClass;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

import com.Employee.Department.Department;
import com.Employee.Employee.Employee;

public class MainApp {
    public static void main(String[] args) {
        SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
        Session session = sessionFactory.openSession();
        Transaction tx = session.beginTransaction();

        Department dept = new Department();
        dept.setDept_name("Modern College");

        Employee emp1 = new Employee();
        emp1.setName("Rakesh");
        Employee emp2 = new Employee();
        emp2.setName("Sagar");

        emp1.setDept(dept);
        emp2.setDept(dept);

        session.save(dept);
        session.save(emp1);
        session.save(emp2);

        tx.commit();
    }
}

<?xml version="1.0" encoding="utf-8"?>
 <!DOCTYPE hibernate-configuration SYSTEM "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">root</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost/EMP_PRACTISE</property>
        <property name="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</property>
        <property name="hibernate.hbm2ddl.auto">create</property>
        <property name="hibernate.show_sql">true</property>
        <mapping class="com.Employee.Department.Department"></mapping>
        <mapping class="com.Employee.Employee.Employee"></mapping>
    </session-factory>
</hibernate-configuration>

Exception in thread "main" org.hibernate.MappingException: Could not determine type for: com.Employee.Department.Department, at table: Employee, for columns: [org.hibernate.mapping.Column(dept)]
    at org.hibernate.mapping.SimpleValue.getType(SimpleValue.java:455)
    at org.hibernate.mapping.SimpleValue.isValid(SimpleValue.java:422)
    at org.hibernate.mapping.Property.isValid(Property.java:226)
    at org.hibernate.mapping.PersistentClass.validate(PersistentClass.java:597)
    at org.hibernate.mapping.RootClass.validate(RootClass.java:265)
    at org.hibernate.boot.internal.MetadataImpl.validate(MetadataImpl.java:329)
    at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:451)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:710)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:726)
    at com.Employee.MainClass.MainApp.main(MainApp.java:13)