hibernate 双向一对多(多对一)

配置hibernate环境

实体类

package com.wd.pojo;

public class Student {
	private Integer id;
	private String name;
	private Teacher teacher;//此处通过t_student中的tid列映射到t_teacher表中的一行记录
	
	public Teacher getTeacher() {
		return teacher;
	}
	public void setTeacher(Teacher teacher) {
		this.teacher = teacher;
	}
	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;
	}
	@Override
	public String toString() {
		return "Student [id=" + id + ", name=" + name + "]";
	}
	public Student(String name) {
		super();
		this.name = name;
	}
	public Student(Integer id, String name) {
		super();
		this.id = id;
		this.name = name;
	}
	public Student() {
		super();
		// TODO Auto-generated constructor stub
	}
	
}

public class Teacher {
	private Integer id;
	private String name;
	private Set<Student> stuSet =new HashSet<>();//此处指定映射Student,注意添加get/set方法
	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;
	}
	public Set<Student> getStuSet() {
		return stuSet;
	}
	public void setStuSet(Set<Student> stuSet) {
		this.stuSet = stuSet;
	}
	public Teacher(Integer id, String name, Set<Student> stuSet) {
		super();
		this.id = id;
		this.name = name;
		this.stuSet = stuSet;
	}
	public Teacher(String name, Set<Student> stuSet) {
		super();
		this.name = name;
		this.stuSet = stuSet;
	}
	public Teacher() {
		super();
		// TODO Auto-generated constructor stub
	}
	@Override
	public String toString() {
		return "Teacher [id=" + id + ", name=" + name + "]";
	}
	
}

映射文件：一定注意inverse控制关联关系

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping SYSTEM "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd" >
<hibernate-mapping>
		<class name="com.wd.pojo.Student" table="t_student">
			<id name="id" column="id">
				<generator class="identity"></generator>
			</id>
			<property name="name" column="name" length="50"></property>
			<!-- 注意此处所指定的是一行记录，并且能够通过tid列映射到t_teacher表格中 -->
			<!-- 若是Teacher.hbm.xml中没有设置inverse可以在此处 insert="false" update="false" -->
			<many-to-one name="teacher" column="tid"/>
		</class>
</hibernate-mapping>

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping SYSTEM "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd" >
<hibernate-mapping>
	<class name="com.wd.pojo.Teacher" table="t_teacher">
		<id name="id" column="id">
			<generator class="identity"></generator>
		</id>
		<property name="name" column="name" length="50" ></property>
		<!-- 此处设置inverse为true或者在Student.hbm.xml文件中设置 insert="false" update="false" -->
		<set name="stuSet" inverse="true">
			<!-- 指定外键，可以通过此键值查询出t_student中的信息 -->
			<!-- column指定的外键值必须是t_student中已经有的字段，否则返回[] -->
			<key column="tid" not-null="true"/>
			<one-to-many class="com.wd.pojo.Student"/>
		</set>
	</class>
</hibernate-mapping>

测试代码

public class HibernateTest {

	@Test
	public void testGet() {
		Session session = null;
		try {
			session = HibernateUtil.getSession();
			session.beginTransaction();
			
//			Student student = (Student) session.get(Student.class, 4);
//			Teacher teacher = student.getTeacher();
//			System.out.println(teacher);
			
//			Teacher teacher = (Teacher) session.get(Teacher.class, 1);
//			Set<Student> stuSet = teacher.getStuSet();
//			for (Student student : stuSet) {
//				System.out.println(student);
//			}
			
			session.getTransaction().commit();
		} catch (Exception e) {
			session.getTransaction().rollback();
			e.printStackTrace();
		} finally {
			if (session != null) {
				session.close();
			}
		}
	}
}