Hibernate关联关系疑问

　　有这样两个持久化对象Person和Book，两者是一对多双向关联关系，对Person.hbm.xml的bag元素设置了cascade="all"属性。下面来看看我的测试类以及测试结果来引出我的疑问。

 

 

package com.aaxis;

import com.aaxis.model.Book;
import com.aaxis.model.Person;
import junit.framework.TestCase;
import org.hibernate.*;
import org.hibernate.cfg.Configuration;

import java.util.ArrayList;
import java.util.List;

/**
 * Created by IntelliJ IDEA.
 * User: Zhong Gang
 * Date: 10/24/11
 * Time: 11:50 AM
 */
public class HibernateCoreTest extends TestCase {

    public void testBook() throws Exception {
        Book book1 = new Book("book1", "booksssssss");
        Book book2 = new Book("book2", "booksssssss");
        List<Book> books = new ArrayList<Book>();
        books.add(book1);
        books.add(book2);
        Person person = new Person("person1", "personsssss", books);
        SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
        Session session = sessionFactory.openSession();
        Transaction transaction = session.beginTransaction();
        session.save(person);
        System.out.println("person's id is " + person.id());
        List<Book> booksAfterFound = person.books();
        for (Book book : booksAfterFound) {
            System.out.println("book's id is " + book.id());
            System.out.println("the person of book's id is " + book.person());
        }
        transaction.commit();
        session.close();
    }
}

 

　　下面是我运行测试的截图

 

 　　按照上述代码，当我在save person后，因为设置了级联book的操作，所以person和book会从瞬时态转化为持久态，这时，我想通过book来获取它的person，但是事实上是book的person为空，因为在save person时，它只发出了三条插入对象的语句，而将两者的一对多关联关系建立的语句却是在事务提交之后才发出来的，造成了从book获取person时为null，如何避免此种情况的发生呢？附上我的源码以供参考。