參考文章: http://viralpatel.net/blogs/hibernate-one-to-many-annotation-tutorial/
One To Many : 一個部門 (department) 有多個員工(employee )
Many To One : 多個員工(employee )屬於一個部門
一對多情況時,必須於 一 與 多的二方設定以上關聯
在 MS SQL 執行 CREATE TABLE
CREATE TABLE dbo.department (
department_id INT IDENTITY(1,1)PRIMARY KEY,
dept_name VARCHAR(50) NOT NULL DEFAULT '0'
);
CREATE TABLE dbo.employee (
employee_id INT IDENTITY(1,1)PRIMARY KEY,
firstname VARCHAR(50) NULL DEFAULT NULL,
lastname VARCHAR(50) NULL DEFAULT NULL,
birth_date DATE NULL DEFAULT NULL,
cell_phone VARCHAR(15) NULL DEFAULT NULL,
department_id INT FOREIGN KEY REFERENCES dbo.department(department_id)
);
Employee.java
import java.sql.Date;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
@Entity
@Table(name="EMPLOYEE")
public class Employee {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name="employee_id")
private Integer employeeId;
@Column(name="firstname")
private String firstname;
@Column(name="lastname")
private String lastname;
@Column(name="birth_date")
private Date birthDate;
@Column(name="cell_phone")
private String cellphone;
@ManyToOne
@JoinColumn(name="department_id")
private Department department;
public Employee() {
}
public Employee(String firstname, String lastname, String phone) {
this.firstname = firstname;
this.lastname = lastname;
this.birthDate = new Date(System.currentTimeMillis());
this.cellphone = phone;
}
public Department getDepartment() {
return department;
}
public void setDepartment(Department department) {
this.department = department;
}
public Integer getEmployeeId() {
return employeeId;
}
public void setEmployeeId(Integer employeeId) {
this.employeeId = employeeId;
}
public String getFirstname() {
return firstname;
}
public String getLastname() {
return lastname;
}
public Date getBirthDate() {
return birthDate;
}
public String getCellphone() {
return cellphone;
}
public void setFirstname(String firstname) {
this.firstname = firstname;
}
public void setLastname(String lastname) {
this.lastname = lastname;
}
public void setBirthDate(Date birthDate) {
this.birthDate = birthDate;
}
public void setCellphone(String cellphone) {
this.cellphone = cellphone;
}
}
Department.java
import java.util.Set;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
@Entity
@Table(name="DEPARTMENT")
public class Department {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name="DEPARTMENT_ID")
private Integer departmentId;
@Column(name="DEPT_NAME")
private String departmentName;
@OneToMany(mappedBy="department")
private Set<Employee> employees;
public Integer getDepartmentId() {
return departmentId;
}
public void setDepartmentId(Integer departmentId) {
this.departmentId = departmentId;
}
public String getDepartmentName() {
return departmentName;
}
public void setDepartmentName(String departmentName) {
this.departmentName = departmentName;
}
public Set<Employee> getEmployees() {
return employees;
}
public void setEmployees(Set<Employee> employees) {
this.employees = employees;
}
}
For TEST
import org.hibernate.Session;
import org.hibernate.SessionFactory;
public class Main {
public static void main(String[] args) {
SessionFactory sf = HibernateUtil.getSessionFactory();
Session session = sf.openSession();
session.beginTransaction();
Department department = new Department();
department.setDepartmentName("Sales");
session.save(department);
Employee emp1 = new Employee("Nina", "Mayers", "111");
Employee emp2 = new Employee("Tony", "Almeida", "222");
emp1.setDepartment(department);
emp2.setDepartment(department);
session.save(emp1);
session.save(emp2);
session.getTransaction().commit();
session.close();
}
}
