Hibernate oneToMany 一对多双向

最新推荐文章于 2025-07-28 23:27:29 发布

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#hibernate #integer #generator #string #class #session

本文详细介绍如何使用Hibernate框架实现一对多关系的实体映射。通过具体步骤指导读者完成数据库表设计、JavaBean实体类创建、Hibernate配置文件设置，并提供测试代码示例。

最近重新静下心来好好复习过去的知识，写写文章让自己映象更加深刻

Hibernate oneToMany实现方式：1、只有2个实体表，关系由多方维护；2、有2个实体表，一个关系表，关系在关系表中提现。如下重点介绍1.只有2个实体表方式；

步骤：

1.SQL 建表 tb_teacher表及tb_student表

CREATE TABLE `tb_teacher` (
`t_id` INT(11) NOT NULL AUTO_INCREMENT,
`t_name` VARCHAR(20) DEFAULT NULL,
PRIMARY KEY (`t_id`)
) ENGINE=INNODB DEFAULT CHARSET=utf8

CREATE TABLE `tb_student` (
`s_id` INT(11) NOT NULL AUTO_INCREMENT,
`s_name` VARCHAR(20) DEFAULT NULL,
`t_id` INT(11) DEFAULT NULL,
PRIMARY KEY (`s_id`),
KEY `fk_student_teacher` (`t_id`),
CONSTRAINT `fk_student_teacher` FOREIGN KEY (`t_id`) REFERENCES `tb_teacher` (`t_id`)
) ENGINE=INNODB DEFAULT CHARSET=utf8

2.创建JavaBean对应的实体对象

Teacher.java

package com.hibernate.entity;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;

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.OrderBy;
import javax.persistence.Table;

import org.hibernate.annotations.GenericGenerator;

@Entity
@Table(name="tb_teacher")
public class Teacher implements Serializable {

private Integer teacherId;
private String teacherName;
private Set<Student> students = new HashSet<Student>();

public Teacher(){}

public Teacher(Integer teacherId,String teacherName){
  this.teacherId = teacherId;
  this.teacherName = teacherName;
}

public Teacher(Integer teacherId,String teacherName,String teacherTel,Set<Student> students){
  this.teacherId = teacherId;
  this.teacherName = teacherName;
  this.students = students;
}

@GenericGenerator(name = "generator", strategy = "increment")
@Id
@GeneratedValue(generator = "generator")
@Column(name="t_id",length=11,nullable=false)
public Integer getTeacherId() {
  return teacherId;
}
public void setTeacherId(Integer teacherId) {
  this.teacherId = teacherId;
}

@Column(name="t_name",length=20)
public String getTeacherName() {
  return teacherName;
}
public void setTeacherName(String teacherName) {
  this.teacherName = teacherName;
}

@OneToMany(mappedBy="teacher",cascade={CascadeType.ALL},targetEntity=Student.class,fetch=FetchType.LAZY)
@OrderBy("studentId")

//一对多的关系注意mappedBy为该类名称只有2个实体表的情况，有关系表则为关系表名称

//orderby为student javaBean的属性
public Set<Student> getStudents() {
return students;
}
public void setStudents(Set<Student> students) {
this.students = students;
}

}

Student.java

package com.hibernate.entity;

import java.io.Serializable;

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 org.hibernate.annotations.GenericGenerator;

@Entity

//实体标注
@Table(name="tb_student")

//标注对应的表
public class Student implements Serializable {

private Integer studentId;
private String studentName;
private Teacher teacher;

public Student(){}

public Student(Integer studentId,String studentName){
  this.studentId = studentId;
  this.studentName = studentName;
}

public Student(Integer studentId,String studentName,Teacher teacher){
  this.studentId = studentId;
  this.studentName = studentName;
  this.teacher = teacher;
}

@GenericGenerator(name="generator",strategy="increment")
@Id
@GeneratedValue(generator="generator")
@Column(name="s_id",length=11,nullable=false)
public Integer getStudentId() {
  return studentId;
}
public void setStudentId(Integer studentId) {
  this.studentId = studentId;
}

@Column(name="s_name",length=20)
public String getStudentName() {
  return studentName;
}
public void setStudentName(String studentName) {
  this.studentName = studentName;
}

@ManyToOne

//多对一的关系
@JoinColumn(name="t_id")

//字段指向表中外键字段
public Teacher getTeacher() {
return teacher;
}
public void setTeacher(Teacher teacher) {
this.teacher = teacher;
}
}

3.Hibernate.cfg.xml配置

<!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
    <hibernate-configuration>
    <session-factory>
       <property name="connection.url">jdbc:mysql://localhost:3306/test</property>
       <property name="connection.username">root</property>
       <property name="connection.password">rootpassword</property>
       <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
       <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
       <property name="current_session_context_class">thread</property>

<mapping class="com.hibernate.entity.Teacher" />
       <mapping class="com.hibernate.entity.Student" />
    </session-factory>
    </hibernate-configuration>

4.测试

package com.hibernate.test;

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

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

import com.hibernate.entity.Student;
import com.hibernate.entity.Teacher;

public class Test {

/**
* @param args
*/
public static void main(String[] args) {
  // TODO Auto-generated method stub
  Teacher teacher = new Teacher();
  teacher.setTeacherName("akvo");
  teacher.setTeacherTel("13222654322");

  Student student1 = new Student();
  student1.setStudentName("aaa");
  student1.setStudentTel("13123123123");
  student1.setTeacher(teacher);

  Student student2 = new Student();
  student2.setStudentName("李华");
  student2.setStudentTel("13197211723");
  student2.setTeacher(teacher);

  Student student3 = new Student();
  student3.setStudentName("李四");
  student3.setStudentTel("13128511723");
  student3.setTeacher(teacher);

  Set<Student> students = new HashSet<Student>();

  students.add(student1);
  students.add(student2);
  students.add(student3);

  student1.setStudentBalance(1000f);
  student2.setStudentBalance(100f);
  student3.setStudentBalance(800f);

  SessionFactory sessionFactory = new AnnotationConfiguration().configure("hibernate.cfg.xml").buildSessionFactory();
  Session session = null;
  Transaction ts = null;
  try {
   session = sessionFactory.getCurrentSession();
   ts = session.beginTransaction();
   session.save(teacher);
   ts.commit();
  } catch (Exception e) {
   // TODO: handle exception
   e.printStackTrace();
   ts.rollback();
  }

}

}