spring mvc中处理多对多的同时存储

问题：

在多对多关系中，例如参考中的学生和教师，如果教师也没有存入数据库，学生也没有存入数据库，如何在他们同时存入数据库时，还建立他们的关系表？

Hibernate的处理：

Student s = new Student();
s.setName("小猪");
Teacher t = new Teacher();
t.setName("小李");
Set<Teacher> t_set = new HashSet<Teacher>();
t_set.add(t);
s.setTeacherList(t_set);
session.save(s);

Spring MVC的处理：

Student s = new Student();
s.setName("小猪");
Teacher t = new Teacher();
t.setName("小李");

[b]teacherDao.save(t);
[/b]

Set<Teacher> t_set = new HashSet<Teacher>();
t_set.add(t);
s.setTeacherList(t_set);

studentDao.save(s);

这样处理的情况是将老师的信息存入DAO，然后将学生信息存入DAO，学生信息存入时关联了对应的老师信息。

参考：
http://blog.csdn.net/liuxianbing119/article/details/7283769
原作者liuxianbing

这部分内容实现多对多如下，

一般情况下，多对多的关联关系是需要中间表的；

情况一：如果中间表仅仅是做关联用的，它里面仅有2个外键做联合主键，则使用ManyToMany（不用写中间表的Model，只需要写出两张主表的model即可）

学生表

@Entity
@Table(name = "T_STUDENT")
@SequenceGenerator(name = "SEQ_STUDENT", sequenceName = "SEQ_STUDENT")
public class Student implements Serializable {
private static final long serialVersionUID = 2524659555729848644L;
private Long id;
private String name;
private Date birthday;
private int sex;
private String address;
private Set<Teacher> teacherList;
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SEQ_STUDENT")
@Column(name = "ID", nullable = false, precision = 22, scale = 0)
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
@Column(name = "NAME")
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Temporal(TemporalType.DATE)
@Column(name = "BIRTHDAY")
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
@Column(name = "sex")
public int getSex() {
return sex;
}
public void setSex(int sex) {
this.sex = sex;
}
@Column(name = "address")
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@ManyToMany(cascade = CascadeType.ALL)
@JoinTable(name = "T_TEACHER_STUDENT",
joinColumns = @JoinColumn(name = "student_id"),
inverseJoinColumns = @JoinColumn(name = "teacher_id"))
public Set<Teacher> getTeacherList() {
return teacherList;
}
public void setTeacherList(Set<Teacher> teacherList) {
this.teacherList = teacherList;
}
}

教师表

@Entity
@Table(name = "T_TEACHER")
@SequenceGenerator(name = "SEQ_TEACHER", sequenceName = "SEQ_TEACHER")
public class Teacher implements Serializable {
private static final long serialVersionUID = 2297316923535111793L;
private Long id;
private String name;
private int sex;
private Set<Student> studentList;
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SEQ_TEACHER")
@Column(name = "ID", nullable = false, precision = 22, scale = 0)
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
@Column(name = "name")
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Column(name = "sex")
public int getSex() {
return sex;
}
public void setSex(int sex) {
this.sex = sex;
}
@ManyToMany(mappedBy = "teacherList", cascade = CascadeType.ALL)
public Set<Student> getStudentList() {
return studentList;
}
public void setStudentList(Set<Student> studentList) {
this.studentList = studentList;
}
}

hibernate.cfg.xml配置2个class类

<mapping class="com.dvn.li.model.Student"/>
<mapping class="com.dvn.li.model.Teacher"/>

测试：

SessionFactory sessionFactory = null;
Session session = null;
try {
sessionFactory = HibernateUtil.getSessionFactory();
session = sessionFactory.getCurrentSession();
session.beginTransaction();
Student s = new Student();
s.setName("小猪");
Teacher t = new Teacher();
t.setName("小李");
Set<Teacher> t_set = new HashSet<Teacher>();
t_set.add(t);
s.setTeacherList(t_set);
session.save(s);

} catch (Exception e) {
if (session != null) {
session.getTransaction().rollback();
}
}