我不知道这是不是更好的方法，但我们找到了一个似乎很成功的方法，如果有人需要，我花几分钟把它写在这里。
基本思想是DTO应该总是更新一个真正的DB实体，只更新它知道的字段，只覆盖Hibernate实体中包含的部分DB状态。这样，我们可以确保实体只在DTO范围内被修改。
否则可能会导致问题，例如一个全新的对象只被部分填充，hVersion过期，问题中提到的id冲突。
要做到这一点，我们有三个部分：

#1Map器的ObjectFactory：

@ApplicationScoped
public class AppMapperDatabaseHandler {

    @PersistenceContext
    private EntityManager em;

    /**
     * Loads database entity from any type from the DTO id.
     * EntityDto is just a contract with id() method.
     */
    @ObjectFactory
    public <E extends BaseEntity> E load(@TargetType @NotNull Class<E> type, @NotNull EntityDto dto) {
        return em.find(type, dto.id());
    }

    /**
     * Same as before, but if the entity is not in the database, uses a Supplier to produces the entity (should come from the business layer).
     * @DatabaseEntityMayBeNew is a custom annotation made to guide mapstruct to know which methods to use.
     */
    @ObjectFactory
    @DatabaseEntityMayBeNew
    public <E extends BaseEntity> E loadOrSupply(@TargetType @NotNull Class<E> type, @NotNull EntityDto dto, @NotNull Supplier<E> supplier) {
        E entity = em.find(type, dto.id());
        return entity != null ? entity : supplier.get();
    }

    /**
     * Merge/persist at the end of the mapping if entity can be new, to ensure it's not transient.
     */
    @AfterMapping
    @DatabaseEntityMayBeNew
    public <E extends BaseEntity> E merge(EntityDto dto, Supplier<E> producer, @MappingTarget E entity) {
        return em.merge(entity);
    }
}

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#2 MapperConfig中的原型定义：

/**
 * Prototype to all "toDb" method, applying the DatabaseEntityMayBeNew qualifier when there is a supplier. This method is never called nor implemented by itself, it's just a mapstruct contract.
 */
@BeanMapping(qualifiedBy = DatabaseEntityMayBeNew.class)
BaseEntity genericToDb(EntityDto dto, Supplier<? extends BaseEntity> producer);

型

#3每个DTO/DB对的几个Map器方法：

// case where the DTO can be mapped to a new entity
Parent toDb(ParentEditDto dto, Supplier<Parent> producer);

// case where the DTO is mapped to an already persisted entity
Parent toDb(ParentRightsDto dto);

型
以下是可以使用这些方法的两种情况：

// in a save REST method, where we use a business handler to create a new entity if needed
Parent parent = parentMapper.toDb(dto, () -> parentHandler.create());
// in another REST method, where the entity is already known
Parent parent = parentMapper.toDb(dto);

型
为了显示结果，下面是由mapstruct生成的方法：

@Override
public Parent toDb(ParentEditDto dto, Supplier<Parent> producer) {
    // ... check params...
    Parent parent = appMapperDatabaseHandler.loadOrSupply( Parent.class, dto, producer );
    // ... call all set()...
    // as you can see, the child entity also uses a toDb() method
    parent.setChild( childMapper.toDb( dto.child() ) );
    // this method contains the following, same as here:
    // Child child = appMapperDatabaseHandler.load( Child.class, dto );
    Parent target = appMapperDatabaseHandler.merge( dto, producer, parent );
    // ...
}

@Override
public Parent toDb(ParentRightsDto dto) {
    // ... check params...
    Parent parent = appMapperDatabaseHandler.load( Parent.class, dto );
    // ... call all set()...
    // ...
}

型