Question

我有2个实体User和UserSettings。我正在尝试构建一个流来修改DB中的UserSettings行。这是我的User和UserSetting对象 -

@Entity
@Table(name = "user")
public class User implements Serializable{


    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    @Column(name = "id")
    private int id;
    private String name;

    @Type(type = "org.jadira.usertype.dateandtime.joda.PersistentDateTime")
    private DateTime createdat = new DateTime();

    @OneToMany( fetch=FetchType.EAGER)
    @JoinColumn(referencedColumnName="id", name = "userID")  
    @BatchSize(size = 50)
    @MapKey(name="name")
    @Cascade({CascadeType.ALL})
    private Map<String,UserSetting> userSetting;


    ...

}


@Entity
@IdClass(UserSetting.UserSettingId.class)
@Table(name = "usersettings")
public class UserSetting implements Serializable{


    @Id
    private String name;

    private String value;

    @Column(name="UserID",insertable = false,updatable = false) //
    private Integer userId;

    @Id
    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name="userID")
    private User user;

    ...
}

在修改UserSetting之前我试图获取对象，修改其值，然后使用save方法。

这是保存修改数据的方法 -

public void saveUserSettings(int userId, String name, String value) {

    UserSetting userSetting = new UserSetting();
    userSetting.setUserId(userId);
    userSetting.setName(name);
    userSetting.setValue(value);

    User user = usersRepository.findOne(userId);
    userSetting.setUser(user);

    userSettingRepository.save(userSetting);
}

保存总是失败，因为从usersRepository.findOne（userId）返回的用户是一个惰性对象而不是实际对象。

为什么会这样？如何让find返回实际对象？

提前谢谢

亚伊尔

Answer 1

使用EntityManager#getReference

@Autowired
    EntityManager em;

    public void saveUserSettings(int userId, String name, String value) {

        UserSetting userSetting = new UserSetting();
        userSetting.setUserId(userId);
        userSetting.setName(name);
        userSetting.setValue(value);

        User user = em.getReference(userId,User.class); // no actual fetch
        userSetting.setUser(user);

        userSettingRepository.save(userSetting);
    }

Answer 2

试试这个：

UserSetting userSettingDb = usersRepository.findOne(userId); User user = userSettingDb.getUser（）; userSetting.setUser（user）;`

userSettingRepository.save(userSetting);`

Answer 3

我通过强制延迟对象返回实现来解决问题（unproxying）。

得到了答案 - https://stackoverflow.com/a/2216603/4797399

使用findOne而不是实际对象时加载Lazy对象（急切）

3 个答案: