Hibernate学习的一个问题

[jaisokforron]

在学习Hibernate的集合映射（用List映射），想做成多对多的List集合映射，单向的能做成功，可是双向的老是报错， Field 't_index' doesn't have a default value可是一个它要什么默认值啊？代码如下，请指教

public class Student {

	private int id;
	private String name;
	private Date creDate;
	private List<Teacher> teachers;……}

public class Teacher {

	private int id;
	private int age;
	private String pro;
	private List<Student> students;……}

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.test.vo">
	<class name="Teacher" table="t_teacher">
	 <id name="id">
	   <generator class="native"/>
	 </id>
	 <property name="pro" column="pro"/>
	 <property name="age" column="age"/>
	  
	
	<list name="students" table="t_teacher_student" cascade="save-update">
	<key column="t_id" not-null="true"></key>
	<index column="s_index"></index>
	<many-to-many class="Student" column="s_id"></many-to-many>
	</list>
	
	 </class>
</hibernate-mapping>

<hibernate-mapping package="com.test.vo">
	<class name="Student" table="t_student">
	 <id name="id">
	   <generator class="native"/>
	 </id>
	 <property name="name" column="sname"/>
	 <property name="creDate" column="credate" type="date"/>
 
	<list name="teachers" table="t_teacher_student" cascade="save-update">
	<key column="s_id" not-null="true"></key>
	<index column="t_index"></index>
	<many-to-many class="Teacher" column="t_id"></many-to-many>
	</list>

	 </class>
</hibernate-mapping>

public class TestSave1 extends TestCase {

	public void save1(){
		Session session=null;
		try {
			session=HibernateSessionFactory.getSession();
			session.beginTransaction();
			Student s1=new Student();
			s1.setName("s1");
			SimpleDateFormat sf=new SimpleDateFormat("yyyy-MM-dd");
			try {
				s1.setCreDate(sf.parse("1988-08-09"));
			} catch (ParseException e) {
				e.printStackTrace();
			}
  
			Student s2=new Student();
			s2.setName("s2");
			try {
				s2.setCreDate(sf.parse("1988-09-08"));
			} catch (ParseException e) {
				e.printStackTrace();
			}
			
			Teacher t1=new Teacher();
		
			List<Student> list=new ArrayList<Student>();
			list.add(s1);
			list.add(s2);
			t1.setAge(77);
			t1.setPro("computer");
			t1.setStudents(list);
		
			session.save(t1);
			session.getTransaction().commit();
		} catch (HibernateException e) {
			e.printStackTrace();
		} catch(Exception ee){
			ee.printStackTrace();
		} finally{
			HibernateSessionFactory.closeSession();
		} }

[huangchbao]

不建议你使用List来映射···因为List映射需要多对多表中要有一个区分字段··是避免重复的！
建议你使用Set来映射
public class Student {

private int id;
private String name;
private Date creDate;
private Set<Teacher> teachers=new HashSet<Teacher>(0);
}
public class Teacher {

private int id;
private String name;
private Date creDate;
private Set<Student> students=new HashSet<Student>(0);
}

在XML配置文件中使用set节点来映射就哦了!

[auklli]

用list还真不知道怎么搞 用set咯 官方也推荐用。。

[handsome_huxiulei]

我也不晓得 没怎么高过..

[hepeng_8]

[Quote=引用 1 楼 huangchbao 的回复:]
不建议你使用List来映射···因为List映射需要多对多表中要有一个区分字段··是避免重复的！
建议你使用Set来映射
public class Student {

private int id;
private String name;
private Date creDate;
private Set<Teacher> teachers=new HashSet……
[/Quote]
tong 一

[auklli]

不能两边都拥有控制权 必须一方放弃维护关系 inverse="true"

[study_liuy]

唉 怎么用还不会呢！

[乱世出英雄]

用set来映射啊！在set的props标签中配置。

[angel]

[Quote=引用 1 楼 huangchbao 的回复:]
不建议你使用List来映射···因为List映射需要多对多表中要有一个区分字段··是避免重复的！
建议你使用Set来映射
public class Student {

private int id;
private String name;
private Date creDate;
private Set<Teacher> teachers=new HashSet……
[/Quote]
+1

[jaisokforron]

我也准备放弃它用Set了，至于业务逻辑，取出来再说，学习了，谢谢……