CODEWITHSUNDEEP
neo4jspring-dataspring-data-neo4j
Jotschi
Jotschi

Reputation: 3632

Neo4j SDN UUID Transaction Handler

I'm using Neo4j 2.1.7 with SDN 3.3.0.RELEASE in embedded mode.

How can i automatically assign UUIDs to new nodes? What is the best practice when trying to achieve this?

Current Solution:

I added a TransactionEventHandler which automatically add a uuid property to every node. Additionally this handler also blocks the commit when someone tries to remove the uuid.

Problems:

With SDN i always have to reload the entity outside of my transaction in order to use the generated uuid. This limits the usefulness of @Transactional. Is there maybe a way to workaround this?

Upvotes: 0

Views: 204

Answers (2)

František Hartman
František Hartman

Reputation: 15086

You have several posibilities

  1. Assign the uuid in entity constructor, the advantage of this is that you can then use the uuid safely in equals and hashCode.

    MyNodeEntity() {
  uuid = UUID.randomUUID.toString()
  ....
}

  2. Use lifecycle events, very useful for cases similar to "add uuid if it is not set"

    @Bean
ApplicationListener<BeforeSaveEvent> beforeSaveEventApplicationListener() {
    return new ApplicationListener<BeforeSaveEvent>() {
        @Override
        public void onApplicationEvent(BeforeSaveEvent event) {
            MyNodeEntity entity = (MyNodeEntity) event.getEntity();
            if (!entity.hasUuid()) {
                entity.setUuid(UUID.randomUUID.toString());
            }
        }
    };
}

  3. Subclass GraphRepository and override save() method - too complicated for something that can be achieved using the lifecycle events

Upvotes: 1

Jotschi
Jotschi

Reputation: 3632

I just enhanced my save method in my entity service implementation which will set the uuid upfront when it determined that the given entity is new.

Entity:

public boolean isNew() {
    return null == getId();
}

EntityServiceImpl:

@Override
public T save(T node) {
    if (node.isNew() && node.getUuid() == null) {
        node.setUuid(UUIDTransactionEventHandler.getUUID());
    }
    return nodeRepository.save(node);
}

Upvotes: 0

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