Adding a list to object in spring

Question

Situation : (Using springs) I have a repository with two methods defined with custom queries

@Query("-----")
public Object getA();
@Query("-----")
public List<Object> getB();

For some reason I don't want to write a join query to retrieve the data,

In the controller I define an end point and in that I can call those methods for which I am able to retrieve the data,

But I would want something like this,

All objects of B should be inside the A Object.

A(Object)
a1:
a2:
a3:
B[3] :
  b1:
  b2:
  b3

How can I do this?

First, you generally shouldn't be calling repository methods directly from your controller. This is what @Service is for. Second, if A has a relation to B, you should be using @JoinTable on a field of A, which would mean that fetching A (@Query("select a from A a")) would give you access to the associated Bs. — beerbajay
– beerbajay, Commented Jul 9, 2015 at 10:16
Thank you beerbajay, The point is when I said "For some reason" I meant this, There are like 10 more entities which has dependency on A (OneToMany) I defined all of them, When I query for A, hibernate is querying for all possible dependencies and retrieving details which I don't want. I would want only A and B in this case. A and D in other case. — Kiran Joshi
– Kiran Joshi, Commented Jul 9, 2015 at 10:33
By default FetchType.LAZY is used and your additional entities should not be fetched in their entirety. You also have the option of defining multiple mapped @Entitys for the same table, so one with all of As fields and then only B. This is redundant and in most situations not a best practice, but maybe your use-case is one of these edge cases where it is acceptable (but probably not). — beerbajay
– beerbajay, Commented Jul 9, 2015 at 10:38
I understood what you are talking and I could achieve that using FetchType.LAZY. This is valid in case where two entities are related but there are situations where I need an object like I have shown and there would not be any relation between them. — Kiran Joshi
– Kiran Joshi, Commented Jul 9, 2015 at 11:02
And Beerbajay, why use service to invoke repository methods? What are the advantages over it if I don't have any business logic to be applied. stackoverflow.com/questions/3688664/… Can you add a real time scenario apart from theoretical explanation given in the above link. — Kiran Joshi
– Kiran Joshi, Commented Jul 9, 2015 at 13:32

Chrstian Beutenmueller · Accepted Answer · 2015-07-09 11:02:31Z

1

Apart from writing a Service that wraps the Repository: Since it seems you are already using Spring Data, you could just write a custom query method, that combines both queries (http://docs.spring.io/spring-data/jpa/docs/current/reference/html/#repositories.single-repository-behaviour).

answered Jul 9, 2015 at 11:02

Chrstian Beutenmueller

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1 Comment

Kiran Joshi Over a year ago

Thank you cbeutenmueller, Probably I might get something by looking in this direction :)

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