JPA 多对多映射更新问题答案

【问题标题】：JPA Many to Many Mapping Update IssueJPA 多对多映射更新问题
【发布时间】：2021-02-21 04:04:13
【问题描述】：

我在更新记录时遇到了多对多映射问题

我有两个名为 Pack 和 Channels 的表，Pack 可能有许多频道，并且频道可以分配给许多包。当我创建包时，我附加了频道，它可以正常工作，但是当我更新一个包上的频道时，所有其他包也会影响删除的分配频道。

添加 2 个 ID 为 3,7 的包后，这里是多对多表

然后在更新包 id 3 之后

更新一个包，然后所有其他包相关的频道将被删除

Pack Class

@ManyToMany(cascade = {CascadeType.MERGE})
@JoinTable(name = "PacksChannels",
        joinColumns = @JoinColumn(name = "pack_id", referencedColumnName = "packId"),
        inverseJoinColumns = @JoinColumn(name = "channel_id", referencedColumnName = "channelId"),
        uniqueConstraints = {@UniqueConstraint(columnNames = {"pack_id", "channel_id"})})
List<Channel> channels;

频道类

@ManyToMany(cascade = {CascadeType.MERGE})
@JoinTable(name = "PacksChannels",
        joinColumns =  @JoinColumn(name = "channel_id", referencedColumnName = "channelId"),
        inverseJoinColumns = @JoinColumn(name = "pack_id", referencedColumnName = "packId"),
        uniqueConstraints = {@UniqueConstraint(columnNames = {"pack_id", "channel_id"})})
@JsonIgnore
List<Pack> packs;

创建包

@Override
public Pack save(Pack pack) {



        Pack savePack = packRepository.save(pack);
        return savePack;
    }

服务层上的更新包

@Override
    public Pack update(Pack pack, String ref) {

      
            //I've method call find pack by ref and I get the pack according to ref user pass and then update the pack.

            Pack newPack = packRepository.findPackByRef(ref).get();
            newPack.setPackName(pack.getPackName());
            newPack.setChannels(pack.getChannels());
            Pack savedPack = packRepository.save(newPack);

            return savedPack;
        }

方式添加频道

enter image description here

Sample Pack Json 传递给更新包方法

{
    "packId": 3,
    "packName": "Test1",
    "ref": "1604905979484.55",
   
    "channels": [
        {
            "channelId": 1,
            "name": "test"
        },
        {
            "channelId": 2,
            "name": "hShenid"
        },
        {
            "channelId": 3,
            "name": "Genesis"
        }
    ]
    
}

【问题讨论】：

那么执行创建和更新的代码在哪里？我们猜猜？
@Smutje 我已经添加了那个代码部分
更新包时，pack.getChannels() 中的频道是否包含对另一个 pack 的引用？还有，pack 是从哪里来的？
@Smutje 我添加了包 json 对象

标签： spring-boot hibernate jpa spring-data-jpa

【解决方案1】：

去掉级联选项后问题就解决了

@ManyToMany()
    @JoinTable(name = "PacksChannels",
            joinColumns = @JoinColumn(name = "pack_id", referencedColumnName = "packId"),
            inverseJoinColumns = @JoinColumn(name = "channel_id", referencedColumnName = "channelId"),
            uniqueConstraints = {@UniqueConstraint(columnNames = {"pack_id", "channel_id"})})
    List<Channel> channels;


@ManyToMany()
@JoinTable(name = "PacksChannels",
        joinColumns =  @JoinColumn(name = "channel_id", referencedColumnName = "channelId"),
        inverseJoinColumns = @JoinColumn(name = "pack_id", referencedColumnName = "packId"),
        uniqueConstraints = {@UniqueConstraint(columnNames = {"pack_id", "channel_id"})})
@JsonIgnore
List<Pack> packs;

【讨论】：