Why jcr:uuid is generating after publishing the content?

[akshaybhujbale]

 Above image shows properties of Arctic surfing page before Publishing.

Above Image shows having jcr:uuid after publishing this page.

Is jcr:uuid genearte after publishing the page only?

[Sachin_Arora_]

No its not necessary. jcr:uuid property is getting added due to the jcr:mixinTypes = mix:referenceable added on the asset. Assets that are not published also would have jcr:uuid property if mix:referenceable mixinType is present.

Please refer this link for more details related to jcr:uuid :

https://developer.adobe.com/experience-manager/reference-materials/spec/jcr/1.0/4.9_Referenceable_No...

For testing you can try adding jcr:mixinTypes[Name[]] = mix:referenceable on any nt:unstructured node. Once you save the property, you will see jcr:uuid automatically created for that node.

[akshaybhujbale]

@Sachin_Arora_ 

what is the usecase of mix:referenceable. type.

So if uuid is not mandetory as you said then is there any property to uniquely identify any page or asset in aem.

[Sachin_Arora_ · Accepted solution]

For mix:referenceable you can refer this community page 

https://experienceleaguecommunities.adobe.com/t5/adobe-experience-manager/what-is-mix-referenceable-...

[ManviSharma]

Hi,

• The mix:referenceable type has the effect of enforcing, on any node to which it is assigned, the presence of a property called jcr:uuid.

• The jcr:uuid property is a protected, auto-created, mandatory property. This means that it is created and administered by the system and can only be read (but not changed or deleted) by the client.

• The job of the jcr:uuid property is to expose the universally unique identifier (UUID) of its node.

• The UUID of a referenceable node is assigned on node creation (or at least on node persistence) by the system itself.

• In a given workspace, there is never more than one node with a given UUID, though there may be nodes that are not mix:referenceable and so do not have UUIDs at all.

• If a node that is not mix:referenceable happens to have a property called jcr:uuid, then this property has no special significance (Note that adding such a property is not recommended: In general, the jcr prefix should be reserved for items defined within the specification, though this restriction may not be enforced by the implementation).

• A repository implementation may make its workspace root nodes mix:referenceable. If so, then the root node of all workspaces must be referenceable, and all must have the same UUID.

[Jörg_Hoh]

When you publish a page, a version is created. And when you create a version of a node it will get a jcr:uuid property added.

(of course there are more reasons why a jcr:uuid is added.)