默认情况下，GORM一对多映射会进行快速获取

Question

Using GORM/Grails 2.3.7/Hibernate 3.6, NO scaffolding.

It's my understanding Hibernate uses lazy loading, so why does my mapping eagerly fetch?

TEAM  ---has many-->  MAILBOX

.

class Team {
   Long id
   Long version

   static hasMany = [mailboxes:Mailbox]
   static mapping = {
      id       sqlType:'number', generator: 'native' 
      version  sqlType:'number'
   }

class Mailbox {
   Long id
   Team team

   static belongsTo = [team:Team]
   static mapping = {
      id       sqlType:'number', generator: 'native' 
   }

Problem

When calling Team.get(id) , the returned object contains all mailboxes, fully instantiated. I was expecting mailboxes to be null unless invoking team.getMailboxes() , is the mapping wrong?

Tried

Removed back-reference in Mailbox:

 class Mailbox {
      Long id
      //Team team
      static belongsTo = Team   //before [team:Team]

Had no impact,

Also confirmed from sql output Hibernate is eargerly fetching the mailboxes:

Hibernate: select team0_.id as id1_0_, team0_.version as version1_0_, team0_.name as name1_0_ from team team0_ where team0_.id=?
Hibernate: select mailboxes0_.team_mailboxes_id as team1_1_0_, mailboxes0_.mailbox_id as mailbox2_0_ from team_mailbox mailboxes0_ where mailboxes0_.team_mailboxes_id=?
Hibernate: select mailbox0_.id as id0_0_, mailbox0_.version as version0_0_, mailbox0_.name as name0_0_ from mailbox mailbox0_ where mailbox0_.id=?

I thought maybe it was related to hibernate cache, but I've disabled it:

hibernate {
    cache.use_second_level_cache = false
    cache.use_query_cache = false
    cache.region.factory_class = 'net.sf.ehcache.hibernate.EhCacheRegionFactory'
    singleSession = false
}

Answer 1

Your understanding of lazy loading is wrong. If you define an object or collection to loaded lazily, it does NOT mean, that they should return a null . Instead, you get a proxy a collection of proxies back, which get "inflated" as soon as you explicitly access the properties of the lazy-loaded object