Question

我正在尝试将List保留在对象Team中。我无法让JPA为我坚持下去。在阅读了一些帖子后，看起来您需要通过List＆lt;＆gt;进行迭代，并单独保留每个帖子。这对我来说似乎不对。 JPA必须有办法自动保持List的自动化。

我是否错过了一种简单的JPA方法来深度坚持这些对象？

团队课程：

@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;
...
}

玩家类：

@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);

添加此代码的代码：

@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为我解决这个问题/指向我正确的帖子，在这里：Understanding annotations and JPA(hibernate)

关键是必须设置反向关系。在上面的示例中，要修复它：

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

一旦设置了关系的两边，它就会持久存储到数据库中。

Answer 2

您可以使用其他方法：

Unidirectional OneToMany： http://en.wikibooks.org/wiki/Java_Persistence/OneToMany#Unidirectional_OneToMany.2C_No_Inverse_ManyToOne.2C_No_Join_Table_.28JPA_2.0_ONLY.29

您仍需要保留Object，然后将其添加到Collection中。

如何使用JPA在集合中保留集合/列表

2 个答案: