Hibernate inverse

inverse主要用在一对多和多对多双向关联上，可以被设置到集合标签<set>上，默认inverse为false。

inverse只对set+one-to-many或many-to-many有效，对many-to-one, one-to-one无效。

hibernate 一对多 单向

classes---->student (one--->many)

类：

one

public class Classes {

private Integer id; 
private String name;
private Set students;

}

many

public class Student {//不用动

private Integer id; 
private String name;

}

hbm.xml

Classes.hbm.xml

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.model">
    <class name="Classes" table="classes" >
        <id name="id" column="id" type="java.lang.Integer">
            <generator class="native" />
        </id>
        <property name="name" column="name" type="java.lang.String" />
        <set name="students">
            <key column="class_id" />
            <one-to-many class="com.model.Student" />
        </set>
    </class>

</hibernate-mapping>

Student.hbm.xml 

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.zd.model">
    <class name="Student" table="student" >
        <id name="id" column="id" type="java.lang.Integer">
            <generator class="native" />          
        </id>
        <property name="name" column="name" length="50" type="java.lang.String" />
    </class>

</hibernate-mapping>

测试用例

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

import junit.framework.TestCase;

import org.hibernate.Session;
import org.hibernate.Transaction;

import com.model.Classes;
import com.model.Student;


public class OneToManyTest extends TestCase {

public void testSave1(){
   Session session = null;
   Transaction ta = null;
   try{
    session = HibernateUtil.getSession();
    ta = session.beginTransaction();
    Student stu1 = new Student();
    stu1.setName("z3");
    Student stu2 = new Student();
    stu2.setName("l4");
   session.save(stu1); //一定要先保存,要不是瞬时对象
    session.save(stu2);
    Set stuSet = new HashSet();
    stuSet.add(stu1);
    stuSet.add(stu2);
    Classes c = new Classes();
    c.setName("Java Class");
    c.setStudents(stuSet);
   session.save(c);
    ta.commit();
   }catch(Exception e){
    e.printStackTrace();
    if(ta != null){
     ta.rollback();
    }
   }finally{
    //关闭session， user变为detached离线对象
    HibernateUtil.closeSession(session);
   }
  
}

Hibernate: insert into student (name) values (?)

Hibernate:insertintostudent(name)values(?)

Hibernate:insertintoclasses(name)values(?)

Hibernate:updatestudentsetclass_id=?whereid=?

Hibernate: update student set class_id=? where id=?

注：表student 的字段class_id必须null（若为not null，就会报错）。多了2条update， 所以one-to-many保存时，不太好，不推荐。