Java 如何使列表（包含对象）持久化

首先，正如您所看到的，我使用Java，特别是NetBeans IDE。 所以，我有一个班上的人，扩展了两个班：教练和运动员

在main中，我创建了一个新的

ArrayList list=new ArrayList（）

然后，我用我创建并持久化的对象填充列表

Trainer tr1=        new Trainer("George","White","England",5665);
Athlete ath1=       new Athlete("Mairy","Willians","France",1,'f',"21/3/1988",68,172,"France");
list.add(ath1);
Athlete ath2=new Athlete("Iggy","Black","USA",2,'f',"10/4/1988",70,175,"U.S.A.");
list.add(ath2);
tr1.setAthletes(list);

em2.persist(tr1);
em2.persist(ath1);
em2.persist(ath2);

（这些字段分别在培训师和运动员课程的构造函数中定义良好

我也让他们坚持不懈

Trainer tr1=        new Trainer("George","White","England",5665);
Athlete ath1=       new Athlete("Mairy","Willians","France",1,'f',"21/3/1988",68,172,"France");
list.add(ath1);
Athlete ath2=new Athlete("Iggy","Black","USA",2,'f',"10/4/1988",70,175,"U.S.A.");
list.add(ath2);
tr1.setAthletes(list);

em2.persist(tr1);
em2.persist(ath1);
em2.persist(ath2);

但最终，尽管运动员和教练们坚持不懈，我列出的名单却并非如此

这就是我的问题开始的地方，我希望这些列表是持久的

Trainer tr1=        new Trainer("George","White","England",5665);
Athlete ath1=       new Athlete("Mairy","Willians","France",1,'f',"21/3/1988",68,172,"France");
list.add(ath1);
Athlete ath2=new Athlete("Iggy","Black","USA",2,'f',"10/4/1988",70,175,"U.S.A.");
list.add(ath2);
tr1.setAthletes(list);

em2.persist(tr1);
em2.persist(ath1);
em2.persist(ath2);

在这里，这些列表正在运行并经过测试，没有问题，但它们在Java级别很好，而不是在ObjectDB级别

我应该重新开始吗

有谁能帮我对付这些家伙吗？我真的需要帮助，这很严重

PS：当然，我已经做了必要的进口，比如

import javax.persistence.*;
import java.util.*;

EntityManagerFactory emf2 = Persistence.createEntityManagerFactory("$objectdb/db/personas2.odb");
EntityManager em2 = emf2.createEntityManager();
em2.getTransaction().begin();
em2.close();
emf2.close();

但最终，尽管运动员和教练们坚持不懈，我列出的名单却并非如此

一些想法：


确保
commit
事务（尽管您提到实体是持久化的）

如果
培训师
和
运动员
之间的一对多关联是双向的（可能显示您的实体），请确保正确设置链接的“另一侧”，如下所示：

Trainer tr1 = new Trainer("George","White","England",5665);
Athlete ath1 = new Athlete("Mairy","Willians","France",1,'f',"21/3/1988",68,172,"France");
ath1.setTrainer(tr1); // set the other side of the link
list.add(ath1);
...
tr1.setAthletes(list);

或者在您的实体中添加方法（在
Trainer
此处）：

并将上述行替换为：

Trainer tr1 = new Trainer("George","White","England",5665);
Athlete ath1 = new Athlete("Mairy","Willians","France",1,'f',"21/3/1988",68,172,"France");
tr1.addToAthletes(ath1);


谢谢，似乎已经足够好了，而且只要稍加努力，我就可以做到完美。非常感谢帕斯卡·Thivent！顺便说一句，关于wtf/分钟度量的笑话真不错。：）