jpa - 如何使用JPA将对象中的Collections/List持久化

Question

我正在尝试将列表保留在对象团队中。我无法让JPA为我坚持下去。阅读了一些帖子后，您似乎需要遍历List <>，并逐一保存每个帖子。这对我来说似乎不对。 JPA必须有一种方法可以自动神奇地保留该列表。

我是否缺少一种轻松持久存储这些对象的简单JPA方法？

团队类:

@Entity
@Table(name = "rahCLUB_TEAM")
public class Team implements Serializable{
....
@OneToMany(fetch=FetchType.EAGER, mappedBy = "team", cascade={CascadeType.PERSIST,  CascadeType.REMOVE})
    private List<Player> players;
...
}

玩家等级:

@Entity
@PrimaryKeyJoinColumn(name="id")
@Table(name = "rahCLUB_PLAYER")

public class Player extends Individual implements Serializable{
 ...
   @ManyToOne
   @JoinTable(name="rahCLUB_PLAYER_TEAM_LINK")
   private Team team;
 ...
 }

JPAClubDAOTest:

//create a valid team code
 ...
 Team team = new Team();
 team.setName("Pittsburgh Pirates");
 team.setLeague("NFL");
 team.setGroup("group");
 team.setLevel("AAA");

 Player player = new Player();
 player.setFirstName("firstNameA");
 player.setLastName("lastNameA");
 player.setEmail("emaila@email.com");
 player.setLogin("loginA");
 player.setJerseyNo(22);
 player.setPosition("fullback");
 Date dob  =new SimpleDateFormat("dd/MM/yyyy").parse("21/11/1986");
 player.setDob(dob);

 Player playerb = new Player();
 playerb.setFirstName("firstNameB");
 playerb.setLastName("lastNameB");
 playerb.setEmail("emailB@email.com");
 playerb.setLogin("loginB");
 playerb.setJerseyNo(15);
 playerb.setPosition("widereceiver");
 Date dobb  =new SimpleDateFormat("dd/MM/yyyy").parse("06/06/1986");
 playerb.setDob(dobb);

 ArrayList<Player> players = new ArrayList<Player>();
 players.add(player);
 players.add(playerb);

 team.setPlayers(players);

 Team queryTeam = em.find(Team.class, team.getId());
 log.debug("checking coach...");

这些都失败了:

assertTrue(queryTeam.getPlayers().size()>0);
assertNotNull(queryTeam.getPlayers().get(0));
assertTrue(queryTeam.getPlayers().size()==2);

添加代码的代码:

@Override
public void createTeam(Team team) throws ClubDAOException {
em.persist(team);
for (Player player : team.getPlayers())
{
   this.createPlayer(player);
   //em.persist(player);
}

Answer 1

好吧，我要回答我自己的问题，因为我想在这里看到一个...

感谢JB Nizet帮我解决这个问题/将我指向正确的位置，这里:Understanding annotations and JPA(hibernate)

关键是必须设置逆关系。在上面的示例中，要解决此问题，请执行以下操作:

player.setTeam(team);
playerb.setTeam(team);

关系的双方都设置好之后，就将其持久保存到数据库中。