Hibernate：多对一-优快云博客

本文介绍Hibernate框架中实现多对一关系的两种方式：单向和双向。通过具体代码示例展示了如何在User和Department两个实体类间建立多对一的关系，并提供XML映射文件及测试代码。

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Hibernate对多对一有两种，分为单向和双向。一般都是采用双向

public class User1 {
	private int id;
	private String name;
	private Department department;

	public Department getDepartment() {
		return department;
	}

	public void setDepartment(Department department) {
		this.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 class Department {
	private Integer id;
	private String name;
	private Set<User1> users;

	public Set<User1> getUsers() {
		return users;
	}

	public void setUsers(Set<User1> users) {
		this.users = users;
	}

	public Department(){}

	public Department(String name) {
		this.name = name;
	}
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}


}

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="cn.itcast.hibernate.domain">

	<class name="User1" table="user1">
		<id name="id" unsaved-value="-1">
			<generator class="native" />
		</id>
		<property name="name"/>
		<many-to-one name="department" column="deptid"/>
	</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="cn.itcast.hibernate.domain">

	<class name="Department" table="Department">
		<id name="id" unsaved-value="-1">
			<generator class="native" />
		</id>
		<property name="name"/>
		<set name="users">
		  <key column="deptid"/>
		  <one-to-many class="User1"/>
		</set>
	</class>
</hibernate-mapping>

测试

import java.util.HashSet;
import java.util.Set;

import org.hibernate.Session;
import org.hibernate.Transaction;

import cn.itcast.hibernate.HibernateUtil;
import cn.itcast.hibernate.domain.Department;
import cn.itcast.hibernate.domain.User1;

public class ManyToOneTest {

	public static void main(String[] args) {
		Session session = null;
		Transaction tx = null;

/*		try {
			session = HibernateUtil.getSession();
			tx = session.beginTransaction();

			Department department = new Department("研发部");

			User1 user1 = new User1();
			user1.setName("小新");
			user1.setDepartment(department);

			session.save(department);
			session.save(user1);

			tx.commit();
		} catch (HibernateException e) {
			if (tx!=null) {
				tx.rollback();
			}
			e.printStackTrace();
		}finally{
			if (session!=null) {
				session.close();				
			}
		}*/

/*		//获得
		try {
			session = HibernateUtil.getSession();

			User1 user1 = (User1)session.get(User1.class, 5);
			System.out.println(user1.getName());

			Department department = user1.getDepartment();
			System.out.println(department.getName());

			session.close();

		} catch (Exception e) {
			e.printStackTrace();
		}*/

		try {
			session = HibernateUtil.getSession();
			tx = session.beginTransaction();

			//新建几个用户
			User1 usera = new User1();
			usera.setName("一号");

			User1 userb = new User1();
			userb.setName("二号");

			Set<User1> users = new HashSet<User1>();
			users.add(usera);
			users.add(userb);

			//新建部门
			Department department = new Department("业务部");
			department.setUsers(users);

			session.save(department);

			session.save(usera);
			session.save(userb);


			tx.commit();
		} catch (Exception e) {
			e.printStackTrace();
		}

	}

}