如何使用休眠更新实体

Question

我有实体用户：

@Entity
@Table(name = "entity_user")
@AttributeOverride(name = "id", column = @Column(name = "user_id"))
public class User extends BaseObject implements Serializable {

    /**
     * Login, unique
     */
    private String email;

    private String username;

    /**
     * Secret for signing-in
     */
    private String password;

    /**
     * Type of user
     */
    private UserType userType;

    @OneToMany(fetch = FetchType.EAGER, cascade = {CascadeType.ALL})
    @JoinTable(name = "view_user_to_requestSet", joinColumns = {
        @JoinColumn(name = "user_id")}, inverseJoinColumns = {
        @JoinColumn(name = "requestSet_id")})
    private Set<RequestSet> setOfRequesSet = new HashSet<>();

    @OneToMany(fetch = FetchType.EAGER, cascade = {CascadeType.ALL})
    @JoinTable(name = "view_user_to_requestSetCreator", joinColumns = {
        @JoinColumn(name = "user_id")}, inverseJoinColumns = {
        @JoinColumn(name = "requestSet_id")})
    private Set<RequestSet> setOfRequesSetCreator = new HashSet<>();

    @OneToMany(fetch = FetchType.EAGER, cascade = {CascadeType.ALL})
    @JoinTable(name = "view_user_to_userTask", joinColumns = {
        @JoinColumn(name = "user_id")}, inverseJoinColumns = {
        @JoinColumn(name = "userTask_id")})
    private Set<UserTask> setOfUserTask = new HashSet<>();

    public User() {
    }

    .
    .
..... GET AND SET

基础对象是：@MappedSuperclass public class BaseObject {

@Id
@GeneratedValue
@Column(name = "entity_id")
private Long id;

/**
 *
 * @return true if the entity hasn't been persisted yet
 */
@Transient
public boolean isNew() {
    return id == null;
}

public Long getId() {
    return id;
}

public void setId(Long id) {
    this.id = id;
}

}

问题是，当我尝试更新对象时，出现错误：

Exception in thread "Thread-15" org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]; constraint [UK_5fa729oayn43ynq4v2y4d9qcn]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement

Caused by: org.hibernate.exception.ConstraintViolationException: could not execute statement

Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry '5' for key 'UK_5fa729oayn43ynq4v2y4d9qcn'

对于我正在使用的更新实体：

@Transactional
public void save(User value){
   em.merge(value);
}

我不知道为什么会出现此错误，如何更新我的对象？感谢您的帮助。

编辑： 我更新：

User u = em.find(persistedType, id); //get user by ID
u.getSetOfRequesSet().add(requestSet); //add one otem to set
userDap.merge(u); //save

Answer 1

看起来您的更新重复了集合中的条目（em.merge）。为了防止重复，您应该显式合并集。按如下操作。

1. 将方法合并添加到用户：

   protected User merge(User other) {
       // Just assign all data members(2 examples here)
       setEmail(other.getEmail());
       ....
       setSetOfRequesSet(other.getSetOfRequesSet());
       ...            
   }
   

2. 准备更新的对象实例：

   User updated = em.find(persistedType, id); //get user by ID
   updated.getSetOfRequesSet().add(requestSet); //add one item to set
   

3. 更新现有的数据库实体：

   User existing = em.find(persistedType, id);
   existing.merge(updated);
   

更新后无需调用 em.merge，因为保存将在事务结束时完成。

您可以在这里找到解释。