关于EJB3.0的多对多映射问题

2008-05-19 08:47:38 123 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

基于EJB3.0的远程方法调用前面我已经转载一边基于weblogic服务器、RMI技术的远程方法调用，现在我们来看一下基于EJB3.0的远程方法调用的实现过程。其实这两种都是一个同样的原理，于weblogic服务器作为中转站。实现服务端与客户端间的参数和返回值的传输，而唯一不同的地方：RMI技术是通过注册的方式写入到weblogic服务器上，而EJB3.0就直接咯，将一个EJB项目发布到weblogic中便可。。。十分简单阅读详情

教师和学生是多对多关联，为此我做了三张表：教师表，学生表和中间表。在对这三张表做测试的时候，我写了这么段代码：
//教师为关系的维护端
TeacherFacadeRemote sdao = (TeacherFacadeRemote)ctx.lookup("TeacherFacade/remote");

Teacher teacher1 = new Teacher();
teacher1.setTcourse("徐德志");
teacher1.setTname("数据结构");

Teacher teacher2 = new Teacher();
teacher2.setTcourse("罗三定");
teacher2.setTname("数字图像");

Student student1 = new Student();
student1.setSclass("软件0302");
student1.setSname("王博");

Student student2 = new Student();
student2.setSclass("软件0301");
student2.setSname("阿标");

Student student3 = new Student();
student3.setSclass("软件0302");
student3.setSname("全中");

Student student4 = new Student();
student4.setSclass("软件0301");
student4.setSname("曹梅");

teacher1.getStudents().add(student1); //teacher1带的学生是student1
teacher1.getStudents().add(student3);

teacher2.getStudents().add(student1); //teacher2带的学生也是student1
teacher2.getStudents().add(student4);
teacher2.getStudents().add(student2);

sdao.save(teacher1);
sdao.save(teacher2);

这样学生表会出现两条student1的纪录，但我只想让学生表存在唯一的学生纪录而中间表里可以存在一个教师对应多个学生这样的纪录，请问有什么办法？
附：
Teacher.java
@ManyToMany(cascade = { CascadeType.ALL }, fetch = FetchType.LAZY)
@JoinTable(name = "teacher_student", catalog = "ejb", joinColumns = { @JoinColumn(name = "teacherid", unique = false, nullable = true, insertable = true, updatable = true) }, inverseJoinColumns = { @JoinColumn(name = "studentid", unique = false, nullable = true, insertable = true, updatable = true) })
public Set<Student> getStudents() {
return this.students;
}
public void setStudents(Set<Student> students) {
this.students = students;
}

Student.java
@ManyToMany(cascade = { CascadeType.ALL }, fetch = FetchType.LAZY, mappedBy = "students")
public Set<Teacher> getTeachers() {
return this.teachers;
}
public void setTeachers(Set<Teacher> teachers) {
this.teachers = teachers;
}

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