java - Hibernate 将父级与分离的子级合并

Question

我遇到了将实体与其集合中一个分离的子实体合并的问题。它抛出异常:org.hibernate.PersistentObjectException:传递给持久化的分离实体:com.adastragrp.cmsms.data.SeedNumber

您可以在这个“test()”方法中看到，我从数据库中获取一些队列并获取其子队列。当它们被发送到“saveQueue()”方法时，它们处于分离状态。在这个方法中，我将它们添加到其他队列中。当合并这个队列时，hibernate会抛出异常。

我怎样才能让它发挥作用？感谢您的回答或解释。

    private void test() {
        List<SeedNumber> list = loadQueue();
        saveQueue(list);
    }

    @Transactional
    private List<SeedNumber> loadQueue() {
        return queueDAO.find("SECONDARY").getSeedNumbers();
    }

    @Transactional
    private void saveQueue(List<SeedNumber> detachedSeeds) {
        Queue q = queueDAO.find("DEFAULT");

        List<SeedNumber> seeds = new ArrayList<>();
        SeedNumber sn = new SeedNumber();
        sn.setPhoneNumber("123456");
        sn.setQueue(q);
        seeds.add(sn);
        for(SeedNumber s : detachedSeeds) {
            s.setQueue(q);
            seeds.add(s);
        }

        q.setSeedNumbers(seeds);            

        q = queueDAO.save(q);
    }

DAO 代码:

public Queue save(Queue entity) {
    if (entity == null) {
        LOG.info("queue is null");
        return null;
    }
    if (getEntityManager().contains(entity)) {
        return entity;
    }

    entity = getEntityManager().merge(entity);

    return entity;
}

这是父类:

@Entity
@Table(name = "CMSMS_QUEUE")
public class Queue {

    @Id
    @Column(name = "ID", length = 40)
    private String id;

    @OneToMany(mappedBy = "queue", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    private List<SeedNumber> seedNumbers;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }   

    public List<SeedNumber> getSeedNumbers() {
        return seedNumbers;
    }

    public void setSeedNumbers(List<SeedNumber> seedNumbers) {
        this.seedNumbers = seedNumbers;
    }
}

这是子类:

@Entity
@Table(name = "CMSMS_SEED_NUMBER")
@SequenceGenerator(name = "SeedNumberSeq", sequenceName = "CMSMS_SEED_NUMBER_SEQ", allocationSize = 1)
public class SeedNumber {

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SeedNumberSeq")
    @Column(name = "ID")
    private Long id;

    @Column(name = "PHONE_NUMBER")
    private String phoneNumber;

    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "QUEUE_ID")
    private Queue queue;


    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getPhoneNumber() {
        return phoneNumber;
    }

    public void setPhoneNumber(String phoneNumber) {
        this.phoneNumber = phoneNumber;
    }

    public Queue getQueue() {
        return queue;
    }

    public void setQueue(Queue queue) {
        this.queue = queue;
    }


}

Answer 1

我认为以下代码有问题:

if (getEntityManager().contains(entity)) {
    return entity;
}

entity = getEntityManager().merge(entity);

return entity;

如果您希望 cascade=MERGE 传播到种子编号列表，则不应跳过对 merge 的调用。

恕我直言，一个更清晰的解决方案是像这样实现 saveQueue :

private void saveQueue(List<SeedNumber> detachedSeeds) {
    Queue queue = queueDAO.find("DEFAULT");

    SeedNumber sn = new SeedNumber();
    sn.setPhoneNumber("123456");
    sn.setQueue(q);
    seedNumberDao.saveSeed(sn);
    for (SeedNumber seed : detachedSeeds) {
        seed.setQueue(queue);
        seedNumberDao.saveSeed(seed);
    }
}

顺便说明一下，将 @Transactional 放在私有(private)方法上没有任何效果。