hibernate笔记-012-多对一双向映射

package com.hibernate.entity;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import org.hibernate.annotations.GenericGenerator;

// 年级
@Entity
@Table(name = "t_grade")
public class Grade implements Serializable {

private static final long serialVersionUID = 554334303764498498L;
@Id
@GeneratedValue(generator = "grade_gen")
@GenericGenerator(name = "grade_gen", strategy = "native")
private int id;
private String name;
@OneToMany(mappedBy = "grade")
private Set<Student> students = new HashSet<Student>();

public int getId() {
return id;
}

public String getName() {
return name;
}

public Set<Student> getStudents() {
return students;
}

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

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

public void setStudents(Set<Student> students) {
this.students = students;
}

}

package com.hibernate.entity;

import java.io.Serializable;
import javax.persistence.CascadeType;
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;

// 学生
@Entity
@Table(name = "t_student")
public class Student implements Serializable {

private static final long serialVersionUID = -2005812841024253872L;
@Id
@GeneratedValue(generator = "student_gen")
@GenericGenerator(name = "student_gen", strategy = "native")
private int id;
private String name;
@ManyToOne(cascade = CascadeType.ALL)
@JoinColumn(name = "grade_id")
private Grade grade;

public Grade getGrade() {
return grade;
}

public int getId() {
return id;
}

public String getName() {
return name;
}

public void setGrade(Grade grade) {
this.grade = grade;
}

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

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

}