英文:
Hibernate initializes collection with immutable list
问题
我有以下实体：
@Entity(name = "courses")
public class Course {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
@Singular
@OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
private Collection<Comment> comments = new ArrayList<>();
@ManyToOne(fetch = FetchType.LAZY, optional = false)
private User createdBy;
public void addComment(Comment comment) {
comments.add(comment);
}
}
当我从数据库加载课程时，评论会被初始化为持久集合（Persistent Bag）。问题出现在当我调用 addComment(comment) 方法时，我会得到以下异常：
Caused by: java.lang.UnsupportedOperationException: null
at java.base/java.util.AbstractList.add(AbstractList.java:153) ~[na:na]
at java.base/java.util.AbstractList.add(AbstractList.java:111) ~[na:na]
at org.hibernate.collection.internal.PersistentBag.add(PersistentBag.java:408) ~[hibernate-core-5.4.18.Final.jar:5.4.18.Final]
看起来 Hibernate 分配的 Persistent Bag 是一个不可变的 Collection.EmptyList，因此无法添加评论。
我需要做哪些更改才能够添加评论呢？
英文:
I have the following entity:
@Entity(name = "courses")
public class Course {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
@Singular
@OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
private Collection<Comment> comments = new ArrayList<>();
@ManyToOne(fetch = FetchType.LAZY, optional = false)
private User createdBy;
public void addComment(Comment comment) {
comments.add(comment);
}
}
When I load a course from the database, comments are initialized with a Persistent Bag. The problem occurs when I call addComment(comment), I then get this exception:
Caused by: java.lang.UnsupportedOperationException: null
at java.base/java.util.AbstractList.add(AbstractList.java:153) ~[na:na]
at java.base/java.util.AbstractList.add(AbstractList.java:111) ~[na:na]
at org.hibernate.collection.internal.PersistentBag.add(PersistentBag.java:408) ~[hibernate-core-5.4.18.Final.jar:5.4.18.Final]
It seems that the Persistant Bag, which hibernates assigns, is a Collection.EmptyList, which is immutable and, as such, no comments can be added.
What do I need to change to be able to add comments?
答案1
得分: 3
好的，以下是您提供的内容的翻译：
好的，看起来 lombok 和 hibernate 并没有像我预期的那样很好地配合起来。此外，我将我的实体用以下 lombok 注解进行了注释：
@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
@Builder
public class Course {
//...
@Singular
@OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
private List<Comment> comments = new ArrayList<>();
}
当我从数据库加载一个实体时，似乎 lombok 使用了构建器模式来创建一个新的实例。这将导致评论（comments）被分配一个空的 Collection 列表，然后由于它是不可变的，就无法添加新的评论。我的解决方法是移除 @Singular 注解，并添加 @Builder.Default 注解。现在会分配一个 new ArrayList<> 而不是不可变的列表。虽然现在无法使用创建的单数构建器方法，但至少可以工作了。
英文:
Ok so it seems like lombok and hibernate where not really working together as I expected. In addition I had my entity annotated with the following lombok notations:
@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
@Builder
public class Course {
//...
@Singular
@OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
private List<Comment> comments = new ArrayList<>();
}
When I loaded an entity from the DB it seems lombok uses the builder pattern to create a new instance. This will result in comment having a Collection.EmptyList assigned and then no new comments can be added since it is immutable. My fix was/is to remove the @Singular and add a @Builder.Default. Now a new ArrayList<>() is assigned instead the immutable list. Now I can't use the created singular builder methods but at least it works.
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