如何使用休眠方式更新实体 [英] How to update entity using hibernate

问题描述

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 公共类BaseObject {

Base object is: @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:

The proble is, when I try to UPDATE object, I am getting errors:

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:

For update entity I am using:

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

我不知道为什么会收到此错误，如何更新对象?谢谢您的帮助.

I am dont know why I am getting this error, how can I update my object? Thank you for your help.

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

推荐答案

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

It looks like your update duplicates entries in the set (em.merge). To prevent the duplication you should merge set explicitly. Do as following.

1. 添加方法合并到用户:

1. Add method merge to User:

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

准备一个更新的对象实例:

Prepare an updated object instance:

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

更新现有的数据库实体:

Update the existing db entity:

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

更新后无需校准即可合并，因为保存只会在事务结束时进行.

Not necessary to cal to em.merge after the update, since save will be just done at the end of a transaction.

您可以在此处找到说明

这篇关于如何使用休眠方式更新实体的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！