非列对象的 Hibernate @Entity 与 Spring @Autowired 冲突

Question

I have a table which contains item descriptions. Items have a price history which can be very extensive. It's that last bit that leads me to avoid using a normal one-to-many Hibernate mapping with lazy loading. Think a price history like ticks on a stock exchange, lots of history.

So I have a cache which works well, it's all wired with Spring, the DAO is injected, the cache manages what needs to be queried vs what it already knows.

So, the "natural" thing is to be able to ask an item about it's price history. Here's some code, which is a slimmed down version of the real thing:

@Entity @Table(name="item")
public class Item {
    @Id
    @Column(name="id")
    private long id;
    @Column(name="name")
    private String name;

    @Autowired
    private PriceCache priceCache;

    /* ...setters, getters for id, name ... */

    public NavigableMap<LocalDateTime,SecurityValue> getPrices(LocalDateTime begTime, LocalDateTime endTime) {
        return priceCache.get(id, begTime, endTime);
    }
}

My original version used all static methods with PriceCache; I want to switch to using an injected bean in part because it will mean I can rewrite the cache as an implementation of an interface which makes it easier to set up unit tests for some bits that aren't in the example; I can create a test cache object that supplies my price history in whatever way I need to the test without ever going to the database.

The problem is that when Spring and Hibernate scan the packages, they seem to conflict over what to do with that @Autowired field; I get the following with some formatting for readability); dbEMF is my EntityManagerFactory:

Exception in thread "main" org.springframework.beans.factory.BeanCreationException:
   Error creating bean with name 'dbEMF' defined in class path resource [applicationContext.xml]:
     Invocation of init method failed;
   nested exception is javax.persistence.PersistenceException:
     [PersistenceUnit: default] Unable to build Hibernate SessionFactory;
   nested exception is org.hibernate.MappingException:
     Could not determine type for: com.example.cache.PriceCache, at table: item, for columns: [org.hibernate.mapping.Column(priceCache)]

Again, the basic code and cache work fine provided I use only static methods with the PriceCache, where I create it as a singleton "manually". Converting it to let Spring handle the creating and injection elsewhere works just fine, too. It's only when I have this mix of Hibernate and Spring that I run into a problem.

I haven't tried going back to using an external XML file for the hibernate config which might solve the issue, or not.

Is there a way to tell Hibernate this is not a column? Or is there a different pattern I should be following to do this sort of thing, maybe some sort of proxy for the Item objects?

Answer 1

you can use @Transient annotation, to indicate it should not be persisted into DB.

Generally speaking, I think if this is an entity, it should not have any autowired cache which is not part of it, but that's a different story

Answer 2

Regarding the discussion in the answer below. Hibernate collections and entities are all proxied objects. Maybe what you can try is to implement a custom HibernateProxy that will manage your collection. As per the docs it seems to be possible (CustomProxies) but I have never done it check here: https://docs.jboss.org/hibernate/orm/5.4/userguide/html_single/Hibernate_User_Guide.html#entity-proxy