Hibernate一对多

一对多关联通过外键连接两个类对应的表,而没有中间集合表。

 

One：

package org.hibernate.domain;

import java.util.Set;

public class Department {
	private int id;
	private String name;
	private Set<Employee> employees;

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public Set<Employee> getEmployees() {
		return employees;
	}

	public void setEmployees(Set<Employee> employees) {
		this.employees = employees;
	}

	@Override
	public String toString() {
		return "Department [id=" + id + ", name=" + name + ", employees="
				+ employees + "]";
	}

}

 

Many:

package org.hibernate.domain;

public class Employee {
	private int id;
	private String name;
	private Department department;

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public Department getDepartment() {
		return department;
	}

	public void setDepartment(Department department) {
		this.department = department;
	}

	@Override
	public String toString() {
		return "Employee [id=" + id + ", name=" + name + ", department="
				+ department + "]";
	}

}

 

映射文件：

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="org.hibernate.domain">
	<class name="Department" table="department">
		<id name="id">
			<generator class="native" />
		</id>

		<property name="name" />
		
		<set name="employees">
			<key column="department_id" />
			<one-to-many class="Employee"/>
		</set>
	</class>
</hibernate-mapping>

 

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="org.hibernate.domain">
	<class name="Employee" table="employee">
		<id name="id">
			<generator class="native" />
		</id>

		<property name="name" />
		<!-- 如果忽略了column这个属性那么默认的外键与实体的属性一致 -->
		<many-to-one name="department" column="department_id" />
	</class>
</hibernate-mapping>

 

测试类：

package org.hibernate.test;

import org.hibernate.Hibernate;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.domain.Department;
import org.hibernate.domain.Employee;
import org.hibernate.util.HibernateUtil;

public class OneToMany {
	public static void main(String[] args) {
		Department department = add();
		department = queryDepartmentByDepartmentId(department.getId());
	}
	
	public static Department add() {
		Session session = null;
		Transaction tx = null;
		
		try {
			Department department = new Department();
			department.setName("department name");

			Employee emp1 = new Employee();
			emp1.setDepartment(department);// 对象模型：建立两个对象的关联
			emp1.setName("emp1 name");

			Employee emp2 = new Employee();
			emp2.setDepartment(department);// 对象模型：建立两个对象的关联
			emp2.setName("emp2 name");

			session = HibernateUtil.getSession();
			tx = session.beginTransaction();
			session.save(department);
			session.save(emp1);
			session.save(emp2);
			tx.commit();
			return department;
		} finally {
			if (session != null)
				session.close();
		}
	}
	
	public static Department queryDepartmentByDepartmentId(int departmentId) {
		Session s = null;
		Transaction tx = null;
		
		try {
			s = HibernateUtil.getSession();
			tx = s.beginTransaction();
			Department department = (Department) s.get(Department.class,
					departmentId);
			Hibernate.initialize(department.getEmployees());
			tx.commit();
			return department;
		} finally {
			if (s != null)
				s.close();
		}
	}
}

 

控制台打印结果：