Hibernate PersistentSet remove（）操作不起作用 [英] Hibernate PersistentSet remove() operation not working

问题描述

 父类{
 @OneToMany（mappedBy = parent，cascade = CasacadeType.ALL）
 Set< Child>儿童; 
} 
 
类子元素{
 @Column（nullable = false）
 @ManyToOne 
父亲; 
 
 
 
 
 
 $ b现在，如果我在Set上执行remove（）操作，它的元素实际上并没有被移除。
 
解决方案
映射应该如下所示：
  public class Parent {
 @OneToMany（mappedBy = parent，cascade = CasacadeType.ALL，orphanRemoval = true）
 Set< Child>儿童; 
 
 public void removeChild（Child child）{
 children.remove（child）; 
 child.setParent（null）; 
} 
} 
 
 public class Child {
 @ManyToOne 
父亲; 
} 
  
正如这篇文章，因为你有一个双向关联，你必须让双方同步。 
 
 
 
因此，最好调用： 
 
 
  parent.removeChild （儿童）; 
  
这样， removeChild 即将删除来自 children  Set的 Child ，并设置 Child  父母与空的关联。
 
I've a Set in my Parent entity as below:
Class Parent {
 @OneToMany(mappedBy = parent, cascade = CasacadeType.ALL)
 Set<Child> children;
}

Class Child {
 @Column(nullable=false)
 @ManyToOne
 Parent parent;
}
Now event if I do a remove() operation on the Set for one of its element it doesn't actually get removed.
解决方案
Your mapping should look like this:
public class Parent { 
    @OneToMany(mappedBy = parent, cascade = CasacadeType.ALL, orphanRemoval = true) 
    Set<Child> children;

    public void removeChild(Child child) {
        children.remove(child);
        child.setParent(null);
    }
}

public class Child {
    @ManyToOne
    Parent parent; 
}
As explained in this article, because you have a bidirectional association you have to have both sides in-sync. 

Therefore, it's good practice to call:
parent.removeChild(child);
This way, removeChild is going to remove the Child from the children Set and also set the Child's parent association to null.

                        
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