Hibernate多对多出问题

Question

在练习Hibernate多对多出现了问题，但是怎么也发现不了问题的所在，很苦恼！希望高人指点错误的所在。 
项目的结构是这样的 
  |---test（包） 
  | |--Course.java 
  | |--ExportDB.java 
  | |--Student.java 
  | |--Test.java 
  | |--Course.hbm.xml 
  | |--Student.hbm.xml 
  |------hibernate.cfg.xml 
Java code
--------------------------
hibernate.cfg.xml文件的配置如下：<hibernate-configuration>
<session-factory>
    <property name="hibernate.connection.username">scott</property>
    <property name="hibernate.connection.url">jdbc:oracle:thin:@localhost:1521:oracle</property>
    <property name="hibernate.dialect">org.hibernate.dialect.Oracle9Dialect</property>
    <property name="hibernate.myeclipse.connection.profile">oracle</property>
    <property name="hibernate.connection.password">tiger</property>
    <property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
    <property name="hibernate.show_sql">true</property>
    <property name="hibernate.format_sql">true</property>
    <mapping resource="test/Course.hbm.xml" />
    <mapping resource="test/Student.hbm.xml" />
</session-factory>
</hibernate-configuration>-------------------------
Student.javapackage test;
import java.io.Serializable;
import java.util.HashSet;public class Student implements Serializable{    private long id;    
    private String name;    
    private HashSet courses = new HashSet();    
    public Student(){}    
    public Student(String name,HashSet courses){
        this.name = name;
        this.courses = courses;
    }
    public HashSet getCourses() {
        return courses;
    }
    public void setCourses(HashSet courses) {
        this.courses = courses;
    }
    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }    
}
************************
Student.hbm.xml
<hibernate-mapping>
    <class name="test.Student" table="d_student">
        <id name="id" type="java.lang.Long">
            <column name="id"></column>
            <generator class="sequence">
                <param name="sequence">stu_seq</param>
            </generator>
        </id>
        <property name="name" type="java.lang.String"></property>
        <set name="courses" table="d_student_course" cascade="all">
            <key column="studentid"></key>
            <many-to-many class="test.Course" column="courseid" outer-join="true"></many-to-many>
        </set>
    </class>
</hibernate-mapping>
----------------------------------
Course.java
package test;import java.io.Serializable;
import java.util.HashSet;public class Course implements Serializable{    private long id;
    private String name;
    private HashSet students = new HashSet();
    public Course(){}
    public Course(String name,HashSet students){
        this.name = name;
        this.students = students;
    }
    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public HashSet getStudents() {
        return students;
    }
    public void setStudents(HashSet students) {
        this.students = students;
    }
}
************************************
Course.hbm.xml<hibernate-mapping>
    <class name="test.Course" table="d_course">
        <id name="id" type="java.lang.Long">
            <column name="id"></column>
            <generator class="sequence">
                <param name="sequence">cou_seq</param>
            </generator>
        </id>
        <property name="name" type="java.lang.String" />
        <set name="students" table="d_student_course" cascade="all" inverse="true">
            <key column="courseid"></key>
            <many-to-many class="test.Student" column="studentid" outer-join="true"></many-to-many>
        </set>
    </class>
</hibernate-mapping>
--------------------------------------------------
ExportDB.java
package test;import org.hibernate.cfg.Configuration;
import org.hibernate.tool.hbm2ddl.SchemaExport;public class ExportDB {    
    public static void main(String[] args){
        Configuration con = new Configuration().configure();
        SchemaExport sche = new SchemaExport(con);
        sche.create(true,true);
    }
}
********************************************
运行ExportDB.java之后，可以看见控制台显示如下：
    drop table d_course cascade constraints    drop table d_student cascade constraints    drop table d_student_course cascade constraints    drop sequence cou_seq    drop sequence stu_seq    create table d_course (
        id number(19,0) not null,
        name varchar2(255 char),
        primary key (id)
    )    create table d_student (
        id number(19,0) not null,
        name varchar2(255 char),
        primary key (id)
    )    create table d_student_course (
        courseid number(19,0) not null,
        studentid number(19,0) not null,
        primary key (studentid, courseid)
    )    alter table d_student_course 
        add constraint FK260A8BDA6972978D 
        foreign key (courseid) 
        references d_course    alter table d_student_course 
        add constraint FK260A8BDA4ECDA955 
        foreign key (studentid) 
        references d_student    create sequence cou_seq    create sequence stu_seq***************************************************
Test.java
package test;import java.util.HashSet;import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;public class Test {    Configuration con;
    SessionFactory factory;
    Session session;
    
    public Test(){
        con = new Configuration().configure();
        factory = con.buildSessionFactory();
    }
    
    public void insert(){
        try{
                session = factory.openSession();
                Student stu1 = new Student();
                Student stu2 = new Student();
                HashSet set1 = new HashSet();
                HashSet set2 = new HashSet();
                Course cou1 = new Course();
                cou1.setName("English");
                Course cou2 = new Course();
                cou2.setName("China");
                set1.add(cou1);
                set1.add(cou2);
                set2.add(cou1);
                set2.add(cou2);
                stu1.setCourses(set1);
                stu2.setCourses(set2);
                
                session.save(stu1);
                session.save(stu2);
                session.beginTransaction().commit();
        }catch(HibernateException hh){
                hh.printStackTrace();
                session.beginTransaction().rollback();
        }finally{
                if(session.isOpen()){
                    session.close();
                }            
        }
    }    
    public static void main(String[] args){
        Test test = new Test();
        test.insert();
    }
}
但是再运行Test.java进行添加数据的时候却出现这个错误，我在网上Google了，但是还是无法查出错误的所在，迫切的希望前辈指点迷津！log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment).
log4j:WARN Please initialize the log4j system properly.
Hibernate: 
    select
        stu_seq.nextval 
    from
        dual
org.hibernate.PropertyAccessException: exception setting property value with CGLIB (set hibernate.cglib.use_reflection_optimizer=false for more info) setter of test.Student.setCourses
---------------------------------------------
真诚感谢您的指点~

Answer 1

 <generator class="increment">
                <param name="sequence">stu_seq </param>
</generator> 
Transaction tr=session.beginTransaction();
session.save(stu1);
session.save(stu2);
tr.commit(); 

Answer 2

这个和主键生成策略是无关的，提示说cglib代理类设置属性时出现异常，可能和你声明set为hashset有关，你把两个类中的set修改为Set接口试一下！！

Answer 3

感觉这段代码有问题
                  Student stu1 = new Student(); 
                Student stu2 = new Student(); 
                HashSet set1 = new HashSet(); 
                HashSet set2 = new HashSet(); 
                Course cou1 = new Course(); 
                cou1.setName("English"); 
                Course cou2 = new Course(); 
                cou2.setName("China"); 
                set1.add(cou1); 
                set1.add(cou2); 
                set2.add(cou1); 
                set2.add(cou2); 
                stu1.setCourses(set1); 
                stu2.setCourses(set2); 
1.Student 的name属性没有赋值。
2.Course 的students集合没有把实体Student添加进去程序改一下你试试
                  Student stu1 = new Student(); 
                stu1.setName("tom");//对name赋值
                Student stu2 = new Student(); 
                stu2.setName("jerry");//对name赋值
                HashSet set1 = new HashSet(); 
                HashSet set2 = new HashSet();                 HashSet setStu1 = new HashSet(); //cou1中用来存放Student的集合
                HashSet setStu2 = new HashSet(); //cou2中用来存放Student的集合
                Course cou1 = new Course(); 
                cou1.setName("English"); 
                Course cou2 = new Course(); 
                cou2.setName("China"); 
                set1.add(cou1);
                setStu1.add(stu1);//学生stu1选了课，把stu1加到集合中 
                set1.add(cou2); 
                setStu2.add(stu1);//学生stu1选了课，把stu1加到集合中
                set2.add(cou1); 
                setStu1.add(stu2);//学生stu2选了课，把stu2加到集合中
                set2.add(cou2);
                setStu2.add(stu2);//学生stu2选了课，把stu2加到集合中                stu1.setCourses(set1); 
                stu2.setCourses(set2);                 cou1.setSudents(setStu1);//注入选了cou1学生的集合
                cou2.setSudents(setStu2);//注入选了cou2学生的集合
                  session.save(stu1); 
                session.save(stu2); 
                session.save(cou1); //保存课程cou1
                session.save(cou2); //保存课程cou2加注释的是我加上去的。结合你原来的程序看看还有什么问题。

Answer 4

4楼你说的好像和楼主出的问题没什么联系呀，Student设置了级联你就不用手动保存Course ，多对多关联映射是根据你对象的关系映射成数据库的关系，操作对象是很随意的事情，哪里会和"students集合没有把实体Student添加进去"有什么关系。