CODEWITHSUNDEEP
javahibernatejpa
Ulug Toprak
Ulug Toprak

Reputation: 1222

Hibernate JPA cascade types

I have read the cascade type definitions multiple times but i just cannot get my head around which one to use for the particular case i am trying to implement.

I have @OneToMany relationship between the Worker class and Task class, so worker can have multiple tasks but each Task is only for one Worker

private List <Task> tasks holds the tasks in the Worker class and private Worker worker; is the Worker object in the Task class

I am stuck at the ? below, don't know which cascade type i should use.

@OneToMany(targetEntity=Task.class, mappedBy="worker", cascade=CascadeType.?, fetch = FetchType.LAZY)

Both objects should exist without one another but i want the changes to Task objects to reflect on the Worker object and vice versa

Ultimately(if i can get this to work :) ) i am suppose to write an algorithm to match the best worker when a new task get entered to the system i want to know if i am on the right track or not. Thanks

Upvotes: 3

Views: 6407

Answers (2)

EasterBunnyBugSmasher
EasterBunnyBugSmasher

Reputation: 1582

This depends on how you are using your entities.

  • If you never detach your entities, then you don't need CascadeType.DETACH. If you do, then you should probably include this CascadeType.
  • When you merge your detached worker back into your persistence context, do you also want its tasks merged? This is not an easy decision, but from what you're saying you probably don't modify a worker and a task in the same process, so you probably don't want this.
  • CascadeType.PERSIST is usually a good choice and you can't really go wrong with this one. But like above: It doesn't sound like you are creating a worker and a new task in the same process. But if you do, then choose this CascadeType.
  • You definitely don't want to use CascadeType.REMOVE from what I understand.

Upvotes: 3

cнŝdk
cнŝdk

Reputation: 32155

Well in your specific case you want to revert changes in one entity to the other side and you don't want to remove it if the mapping entity is removed, to answer both your requirements:

Both objects should exist without one another

In that case you should not use CascadeType.REMOVE type because it emoves all related entities association with this setting when the owning entity is deleted.

but i want the changes to Task objects to reflect on the Worker

In that case using the CascadeType.PERSIST and CascadeType.MERGE types will be sufficient to reflect changes between both sides as CascadeType.PERSIST covers both save() and persist() operations while CascadeType.MERGE will handle the merge() operation.

For further details about this topic I suggest reading HowToDoInJava Hibernate JPA Cascade Types article as it briefly illustartes all these cases.

Upvotes: 4

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