@ManyToMany级联= CascadeType.REMOVE删除关联和实体 [英] @ManyToMany with cascade = CascadeType.REMOVE removes associations AND entities

问题描述

我有2个实体： Group 和分组，其中1个ManyToMany关联。在数据库中，关联表在组中都有一个NOT NULL FK。 / code>和分组。

我想让Hibernate删除关联，但不是删除分组实体的代码：

@Autowired
private final GroupedRepository groupedRepository;

public void delete（grouped groupedToRemove）{
groupedRepository.delete（groupedToRemove）;如果我将 cascade = CascadeType.ALL


code>或 cascade = CascadeType.REMOVE ，我的 Group 实体被删除，当我删除分组实体，不仅是关联：
$ b

  @ ManyToMany（cascade = CascadeType.ALL，//与CascadeType.REMOVE相同的行为
 mappedBy =分组，
 targetEntity = Group.class）
私人设置< Group> groups = new HashSet<>（）; 
  

如果我删除级联，hibernate会尝试设置group_id = null，并且会引发 ModelConstraintException 。我不想将FK设置为​​空。

组实体：

  @Entity 
 @Table（name =groups）
 @Getter 
 @Setter 
 public class Group {
 
 @Id 
 @GeneratedValue（strategy = GenerationType.AUTO）
 private Integer id; 
 
 @ManyToMany（targetEntity = Grouped.class）
 @JoinTable（
 name =association，
 joinColumns = @JoinColumn（name =group_id，nullable = false，updatable = false），
 inverseJoinColumns = @JoinColumn（name =grouped_id，nullable = false，updatable = false）
）
 private Set< Grouped> groupped = new HashSet<>（）; 
 
  

分组实体：

< pre-class =lang-java prettyprint-override> @Entity
@Table（name =grouped）
@Getter
@Setter
public class分组{b
$ b @Id
@GeneratedValue（strategy = GenerationType.AUTO）
私有整数id;

@ManyToMany（mappedBy =groupped，targetEntity = Group.class）
private Set< Group> groups = new HashSet<>（）;
}


解决方案

这是预期的行为。删除级联意味着：删除此实体时，还要删除关联的实体。在ManyToXxx上没有任何意义，因为很明显，其他实体仍在引用相关实体。

如果您想要删除一个分组，但将关联的组留在那里，您需要先删除两个实体之间的关联：

  for（Group group：grouped.getGroups（））{
 group.getGrouped（）。remove（grouped）; 
} 
 grouped.getGroups（）。clear（）; 
  

，然后删除与任何组无关的分组实体。

I have 2 entities: Group and Grouped, with 1 ManyToMany association.

In database, the Association table has a NOT NULL FK on both Group and Grouped.

I want Hibernate to delete the association but not the group when all grouped are deleted.

Code to delete a Grouped entity:

@Autowired
private final GroupedRepository groupedRepository;

public void delete(Grouped groupedToRemove) {
    groupedRepository.delete(groupedToRemove);
}

If I set cascade = CascadeType.ALL or cascade = CascadeType.REMOVE, my Group entities are deleted when I delete a Grouped entity, not only the associations:

@ManyToMany(cascade = CascadeType.ALL, // same behavior with CascadeType.REMOVE
        mappedBy = "grouped", 
        targetEntity = Group.class)
private Set<Group> groups = new HashSet<>();

If I remove the cascade, hibernate tries to set group_id=null and it throws a ModelConstraintException. I don't want to set the FK as nullable.

Group entity:

@Entity
@Table(name = "groups")
@Getter
@Setter
public class Group {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;

    @ManyToMany(targetEntity = Grouped.class)
    @JoinTable(
            name = "association",
            joinColumns = @JoinColumn(name = "group_id", nullable = false, updatable = false),
            inverseJoinColumns = @JoinColumn(name = "grouped_id", nullable = false, updatable = false)
    )
    private Set<Grouped> grouped= new HashSet<>();
}

Grouped entity:

@Entity
@Table(name = "grouped")
@Getter
@Setter
public class Grouped {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;

    @ManyToMany(mappedBy = "grouped", targetEntity = Group.class)
    private Set<Group> groups= new HashSet<>();
}

解决方案

That's the expected behavior. REMOVE cascading means: when removing this entity, also remove the associated entities. It makes no sense on a ManyToXxx, since obviously, other entities are still referencing the associated entity.

If you want to delete a Grouped, but leave the associated Groups there, you need to remove the association between the two entities first:

for (Group group : grouped.getGroups()) {
    group.getGrouped().remove(grouped);
}
grouped.getGroups().clear();

and then remove the Grouped entity, which is not associated to any Group anymore.

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