Reduce footprint due to RootBeanDefinition [SPR-11343]

[spring-projects-issues]

AdiB opened SPR-11343 and commented

Related to #12149
RootBeanDefinition members (externallyManagedConfigMember, externallyManagedInitMethods,externallyManagedDestroyMethods) are initialized even if not in use.
Setting ConcurrentHashMap initial size as 0 is not good enough it still allocates a map with ~ 10 empty elements.

Should delay the initialization.

For example -

public void registerExternallyManagedConfigMember(Member configMember) {
    if (externallyManagedConfigMembers == null){
        externallyManagedConfigMembers = new ConcurrentHashMap<Member, Boolean>(0);
    }
	this.externallyManagedConfigMembers.put(configMember, Boolean.TRUE);
}

public boolean isExternallyManagedConfigMember(Member configMember) {
    if (externallyManagedConfigMembers == null){
        return false;
    }
	return this.externallyManagedConfigMembers.containsKey(configMember);
}

---

Affects: 3.2.6, 4.0 GA

Issue Links:

• Reduce footprint due to BeanDefinitions [SPR-7491] #12149 Reduce footprint due to BeanDefinitions

Referenced from: commits d9ab6aa, a599b57

Backported to: 3.2.7

[spring-projects-issues]

Juergen Hoeller commented

Looking at the current code paths that call those methods, we can conveniently reuse the existing postProcessingLock which will typically be active already when registerExternallyManaged* calls come in from the bean factory's post-processing phase. Since that's a regular synchronized lock, we can also safely lazily initialize regular HashSets for those externallyManaged* holders.

Note that with ConcurrentHashMaps, lazily initializing them introduces a race condition. Simply speaking, ConcurrentHashMaps need to be initialized as final fields, otherwise we'd need some form of synchronization for the lazy creation of each ConcurrentHashMap itself.

Juergen